bench("should never throw", async () => {
    await fc.assert(
      fc.asyncProperty(
        fc.string({ unit: "grapheme-composite" }),
        async (input) => {
          expect(await parse(input)).toBeTruthy();
        },
      ),
    );
  })

Summary: The `parse` function should never throw an error for any grapheme-composite string input, always returning a truthy value.


unknown

test("at-first", (t) => {
    fc.assert(
        fc.property(
            fc.array(
                fc.nat().map((v) => v * 2 ** -32),
                { minLength: 10 }
            ),
            (values) => {
                const treeList = AvlList.empty<number>()
                const expected: number[] = []

                values.sort()
                values.forEach((val) => {
                    const index = asU32Between(0, treeList.length + 1, val)
                    treeList.insert(index, val)
                    expected.splice(index, 0, val)
                })

                const built: number[] = []
                for (const v of treeList) {
                    built.push(v)
                }

                t.deepEqual(built, expected)
            }
        )
    )
})

Summary: An `AvlList` constructed with sorted, inserted values should yield the same sequence when iterated as the expected order.


it('should ensure smooth grade-to-grade transitions', () => {
      fc.assert(
        fc.property(
          fc.tuple(domainArbitraries.grade, domainArbitraries.grade),
          fc.array(domainArbitraries.curriculumCode, { minLength: 3, maxLength: 10 }),
          ([fromGrade, toGrade], expectations) => {
            // Property: Grade transitions should have concept overlap
            if (Math.abs(toGrade - fromGrade) !== 1) {
              return true; // Only test adjacent grades
            }

            if (fromGrade >= toGrade) {
              return true; // Only test upward progression
            }

            // Mock function to get concept difficulty
            const getConceptDifficulty = (code: string, grade: number): number => {
              const baseCode = code.charAt(0);
              const level = parseInt(code.charAt(1));
              return (baseCode.charCodeAt(0) - 65) * 5 + level + grade;
            };

            const fromGradeConcepts = expectations.map((code) =>
              getConceptDifficulty(code, fromGrade),
            );
            const toGradeConcepts = expectations.map((code) => getConceptDifficulty(code, toGrade));

            // Should have some overlap in concept difficulty ranges
            const fromMax = Math.max(...fromGradeConcepts);
            const toMin = Math.min(...toGradeConcepts);

            return fromMax >= toMin; // Some overlap exists
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Grade-to-grade transitions should exhibit overlapping concept difficulties for adjacent, upward progression.


it('should provide appropriate scaffolding reduction', () => {
      fc.assert(
        fc.property(
          domainArbitraries.grade,
          fc.integer({ min: 1, max: 10 }), // scaffolding level
          (grade, scaffoldingLevel) => {
            // Property: Scaffolding should decrease as grade increases
            const maxScaffoldingForGrade = (gradeLevel: number): number => {
              if (gradeLevel <= 2) return 10; // High scaffolding
              if (gradeLevel <= 4) return 7; // Medium scaffolding
              if (gradeLevel <= 6) return 5; // Reduced scaffolding
              return 3; // Minimal scaffolding
            };

            const maxScaffolding = maxScaffoldingForGrade(grade);
            return scaffoldingLevel <= maxScaffolding;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Scaffolding should decrease as grade level increases, ensuring the scaffolding level is within the expected maximum for each grade.


it('can open or close', () => {
    const g = new Goma1015()
    //check definition
    expect(g.open).toBeDefined()
    expect(g.close).toBeDefined()
    expect(g.state).toBeDefined()

    //default is close
    expect(g.state() === State.OFF_CLOSE).toBe(true)

    //property based testing for open/close
    fc.assert(
      fc.property(fc.boolean(), b => {
        if (b) {
          g.open()
          expect(g.state() === State.OFF_OPEN).toBe(true)
          return
        }
        g.close()
        expect(g.state() === State.OFF_CLOSE).toBe(true)
      }),
    )
  })

Summary: The `Goma1015` instance should transition between `OFF_OPEN` and `OFF_CLOSE` states based on the `open` and `close` calls.


it('should handle split-grade curriculum alignment', () => {
      fc.assert(
        fc.property(
          fc.tuple(domainArbitraries.grade, domainArbitraries.grade),
          domainArbitraries.subject,
          ([grade1, grade2], subject) => {
            // Property: Split grades should have feasible curriculum overlap
            if (grade1 === grade2) {
              return true; // Single grade, no split
            }

            const [lowerGrade, higherGrade] = grade1 < grade2 ? [grade1, grade2] : [grade2, grade1];
            const gradeGap = higherGrade - lowerGrade;

            // Split grades should be adjacent or at most 2 grades apart
            if (gradeGap > 2) {
              return false; // Too wide a gap for effective split-grade teaching
            }

            // Core subjects can handle 1-2 grade splits better than others
            const coreSubjects = ['Mathematics', 'Language Arts'];
            if (coreSubjects.includes(subject)) {
              return gradeGap <= 2;
            } else {
              return gradeGap <= 1;
            }
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Split-grade curriculum should have a feasible overlap, with core subjects accommodating up to a 2-grade gap and other subjects accommodating up to a 1-grade gap.


it('should show increasing complexity trends across grades', () => {
      fc.assert(
        fc.property(
          fc.array(domainArbitraries.curriculumProgression, { minLength: 20, maxLength: 50 }),
          (progressions) => {
            // Property: Average complexity should increase with grade level
            const gradeGroups = new Map<number, string[]>();

            progressions.forEach((prog) => {
              if (!gradeGroups.has(prog.grade)) {
                gradeGroups.set(prog.grade, []);
              }
              gradeGroups.get(prog.grade)!.push(prog.complexity);
            });

            const gradeComplexityAverages = new Map<number, number>();

            for (const [grade, complexities] of gradeGroups) {
              const complexityScores = complexities.map((c) => {
                switch (c) {
                  case 'basic':
                    return 1;
                  case 'intermediate':
                    return 2;
                  case 'advanced':
                    return 3;
                  default:
                    return 1;
                }
              });

              const average =
                complexityScores.reduce((sum, score) => sum + score, 0) / complexityScores.length;
              gradeComplexityAverages.set(grade, average);
            }

            // Check if complexity generally increases with grade
            const grades = Array.from(gradeComplexityAverages.keys()).sort((a, b) => a - b);

            if (grades.length < 3) return true; // Need at least 3 grades to test trend

            let increasingTrend = 0;
            for (let i = 1; i < grades.length; i++) {
              const prevAvg = gradeComplexityAverages.get(grades[i - 1])!;
              const currAvg = gradeComplexityAverages.get(grades[i])!;

              if (currAvg >= prevAvg) {
                increasingTrend++;
              }
            }

            // At least 70% of transitions should show increasing complexity
            const trendRatio = increasingTrend / (grades.length - 1);
            return trendRatio >= 0.7;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Average complexity should generally increase with grade level, with at least 70% of grade transitions showing an increase in complexity.


it('should maintain curriculum expectation integrity', () => {
      fc.assert(
        fc.property(domainArbitraries.fullCurriculumExpectation, (expectation) => {
          // Invariant: Curriculum expectations must satisfy business rules
          const hasValidId = expectation.id && expectation.id.length > 0;
          const hasValidCode = /^[A-E][1-5]\.[1-9]|10$/.test(expectation.code);
          const hasValidGrade = expectation.grade >= 1 && expectation.grade <= 8;
          const hasValidDescription = expectation.description.trim().length > 0;
          const hasValidStrand = expectation.strand.trim().length > 0;
          const hasValidSubject = expectation.subject.trim().length > 0;

          // Bilingual consistency
          const bilingualConsistent =
            !expectation.descriptionFr || expectation.descriptionFr.trim().length > 0;

          return (
            hasValidId &&
            hasValidCode &&
            hasValidGrade &&
            hasValidDescription &&
            hasValidStrand &&
            hasValidSubject &&
            bilingualConsistent
          );
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Curriculum expectations must satisfy rules regarding valid ID, code, grade, description, strand, subject, and bilingual consistency.


it('should detect potential issues with the Goma1015', () =>
    fc.assert(
      fc.property(Goma1015Commands, commands => {
        const real = new Goma1015()
        const model = new Goma1015Model()
        fc.modelRun(() => ({ model, real }), commands)
      }),
    ))

Summary: The test checks whether executing a sequence of `Goma1015Commands` on both a `Goma1015` instance and a `Goma1015Model` maintains consistent behavior between the real and model instances.


test("Property-based testing (fast-check)", () => {
  type Boundaries = {
    min: number;
    max: number;
  };

  const minmax =
    ({ min, max }: Boundaries) =>
    (n: number): number =>
      Math.min(max, Math.max(min, n));

  fc.assert(
    fc.property(fc.integer(), (n): boolean => {
      const result = minmax({ min: 1, max: 10 })(n);
      return 1 <= result && result <= 10;
    })
  );
})

Summary: The function `minmax` restricts an integer to a specified range, ensuring the output is between 1 and 10.


it('should maintain curriculum code uniqueness', () => {
      fc.assert(
        fc.property(
          fc.array(domainArbitraries.curriculumCode, { minLength: 10, maxLength: 50 }),
          (codes) => {
            // Invariant: Curriculum codes should be unique within a subject/grade
            const codeFrequency = new Map<string, number>();

            codes.forEach((code) => {
              codeFrequency.set(code, (codeFrequency.get(code) || 0) + 1);
            });

            // Check for duplicates
            const hasDuplicates = Array.from(codeFrequency.values()).some((count) => count > 1);

            // Property: We can detect uniqueness violations
            return typeof hasDuplicates === 'boolean';
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Curriculum codes should be unique within a subject/grade, with the test ensuring the ability to detect violations of uniqueness.


it('calculates dice maximum correctly', () => {
    fc.assert(
      fc.property(
        // count
        fc.integer({ min: 1, max: 1000000 }),
        // sides
        fc.integer({ min: 1, max: 1000000 }),
        (sides, count) => {
          const dice = new SimpleDiceGroup(sides, count);

          expect(dice.statProps.max).toBe(count * sides);
        },
      ),
    );
  })

Summary: `SimpleDiceGroup` calculates the maximum possible sum correctly for dice groups given the number of sides and count.


it('should maintain unit plan temporal consistency', () => {
      fc.assert(
        fc.property(domainArbitraries.unitPlan, (unitPlan) => {
          // Invariant: Unit plans must have valid temporal relationships
          const hasValidDates = unitPlan.startDate < unitPlan.endDate;
          const hasPositiveDuration = unitPlan.estimatedHours > 0;

          // Duration should be reasonable for the time period
          const durationMs = unitPlan.endDate.getTime() - unitPlan.startDate.getTime();
          const durationDays = durationMs / (1000 * 60 * 60 * 24);
          const reasonableDuration = durationDays >= 5 && durationDays <= 60; // 5 days to 2 months

          return hasValidDates && hasPositiveDuration && reasonableDuration;
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Unit plans must have valid temporal relationships, including start and end dates, positive estimated hours, and a reasonable duration between 5 and 60 days.


it('should maintain unit plan content integrity', () => {
      fc.assert(
        fc.property(domainArbitraries.unitPlan, (unitPlan) => {
          // Invariant: Unit plans must have meaningful content
          const hasValidTitle = unitPlan.title.trim().length > 0;
          const hasValidGrade = unitPlan.grade >= 1 && unitPlan.grade <= 8;
          const hasValidSubject = unitPlan.subject.trim().length > 0;

          return hasValidTitle && hasValidGrade && hasValidSubject;
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Unit plans should have a non-empty title, a grade within the range of 1 to 8, and a non-empty subject.


it('should maintain lesson plan structure integrity', () => {
      fc.assert(
        fc.property(domainArbitraries.fullLessonPlan, (lessonPlan) => {
          // Invariant: Lesson plans must have valid structure
          const hasValidId = lessonPlan.id && lessonPlan.id.length > 0;
          const hasValidTitle = lessonPlan.title.trim().length > 0;
          const hasValidDuration = lessonPlan.duration >= 15 && lessonPlan.duration <= 120;
          const hasValidGrade = lessonPlan.grade >= 1 && lessonPlan.grade <= 8;
          const hasValidSubject = lessonPlan.subject.trim().length > 0;

          // Three-part lesson structure (ETFO requirement)
          const hasValidStructure =
            lessonPlan.mindsOn.trim().length > 0 &&
            lessonPlan.action.trim().length > 0 &&
            lessonPlan.consolidation.trim().length > 0;

          return (
            hasValidId &&
            hasValidTitle &&
            hasValidDuration &&
            hasValidGrade &&
            hasValidSubject &&
            hasValidStructure
          );
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Lesson plans must have a valid ID, title, duration, grade, subject, and a three-part structure.


it('should maintain daybook entry reflection structure', () => {
      fc.assert(
        fc.property(domainArbitraries.daybookEntry, (entry) => {
          // Invariant: Daybook entries must have valid reflection data
          const hasValidId = entry.id && entry.id.length > 0;
          const hasValidDate = entry.date instanceof Date && !isNaN(entry.date.getTime());
          const hasValidRating =
            !entry.overallRating || (entry.overallRating >= 1 && entry.overallRating <= 5);
          const hasValidReusability =
            entry.wouldReuseLesson === undefined || typeof entry.wouldReuseLesson === 'boolean';

          return hasValidId && hasValidDate && hasValidRating && hasValidReusability;
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Daybook entries must have non-empty IDs, valid dates, optional ratings between 1 and 5, and an optional boolean for lesson reusability.


it('parses fudge dice', () => {
    fc.assert(
      fc.property(
        // number of dice
        fc.integer({ min: 1, max: 1000000 }),
        (n) => {
          const parseText = `${n}dF`;
          const parseResult = parse(parseText);
          expect(parseResult.lexErrors).toHaveLength(0);
          expect(parseResult.parseErrors).toHaveLength(0);
        },
      ),
    );
  })

Summary: Parsing a string representing fudge dice results in no lexical or parse errors.


it('should maintain calendar event temporal constraints', () => {
      fc.assert(
        fc.property(
          fc.record({
            id: fc.integer({ min: 1, max: 1000000 }),
            title: fc.string({ minLength: 1, maxLength: 100 }),
            start: fc.date(),
            end: fc.date(),
            allDay: fc.boolean(),
            eventType: fc.constantFrom('PD_DAY', 'ASSEMBLY', 'TRIP', 'HOLIDAY', 'CUSTOM'),
          }),
          (event) => {
            // Invariant: Calendar events must have valid temporal relationships
            const hasValidId = event.id > 0;
            const hasValidTitle = event.title.trim().length > 0;
            const hasValidTimeOrder = event.start <= event.end;

            // All-day events should span at least one day
            const validAllDay =
              !event.allDay || event.end.getTime() - event.start.getTime() >= 24 * 60 * 60 * 1000;

            return hasValidId && hasValidTitle && hasValidTimeOrder && validAllDay;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Calendar events must have a valid ID, non-empty title, correctly ordered start and end times, and if marked as all-day, must span at least one day.


it('parses simple dice expressions', () => {
    fc.assert(
      fc.property(
        // number of dice
        fc.integer({ min: 1, max: 1000000 }),
        // number of sides
        fc.integer({ min: 1, max: 1000000 }),
        // modifier value3
        fc.integer({ min: 1, max: 1000000 }),
        // modifier function
        fc.integer({ min: 0, max: 3 }).map((v) => {
          if (v === 0) {
            return '+';
          }
          if (v === 1) {
            return '-';
          }
          if (v === 2) {
            return '*';
          }
          // default 3... why not switch
          return '/';
        }),
        (n, s, m, f) => {
          const parseText = `${n}d${s}${f}${m}`;
          const parseResult = parse(parseText);
          expect(parseResult.lexErrors).toHaveLength(0);
          expect(parseResult.parseErrors).toHaveLength(0);
        },
      ),
    );
  })

Summary: Parses dice expressions consisting of a number of dice, sides, and a modifier without producing lexing or parsing errors.


it('should maintain parent-child relationships', () => {
      fc.assert(
        fc.property(
          fc.record({
            longRangePlan: domainArbitraries.longRangePlan,
            unitPlans: fc.array(domainArbitraries.unitPlan, { minLength: 1, maxLength: 5 }),
          }),
          (planHierarchy) => {
            // Invariant: Child records must reference valid parent
            const { longRangePlan, unitPlans } = planHierarchy;

            // All unit plans should reference the long range plan
            const validReferences = unitPlans.every((unit) => {
              // In real system, unit.longRangePlanId would equal longRangePlan.id
              // Here we check subject/grade consistency as a proxy
              return unit.subject === longRangePlan.subject && unit.grade === longRangePlan.grade;
            });

            return validReferences;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Unit plans should reference a long range plan with consistent subject and grade.


it('should maintain curriculum expectation relationships', () => {
      fc.assert(
        fc.property(
          fc.record({
            expectation: domainArbitraries.fullCurriculumExpectation,
            lessonPlans: fc.array(domainArbitraries.fullLessonPlan, { minLength: 1, maxLength: 3 }),
          }),
          (relationship) => {
            // Invariant: Lesson plans should align with curriculum expectations
            const { expectation, lessonPlans } = relationship;

            const validAlignment = lessonPlans.every(
              (lesson) =>
                lesson.grade === expectation.grade && lesson.subject === expectation.subject,
            );

            return validAlignment;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Lesson plans align with curriculum expectations by matching both grade and subject.


it('should enforce teacher workload limits', () => {
      fc.assert(
        fc.property(
          fc.record({
            teacherId: fc.integer({ min: 1, max: 1000 }),
            dailyLessons: fc.array(domainArbitraries.fullLessonPlan, {
              minLength: 1,
              maxLength: 10,
            }),
          }),
          (teacherDay) => {
            // Invariant: Teachers should not be overloaded
            const { dailyLessons } = teacherDay;

            // Same day lessons
            const sameDay = dailyLessons.filter(
              (lesson) => lesson.date.toDateString() === dailyLessons[0].date.toDateString(),
            );

            const totalDuration = sameDay.reduce((sum, lesson) => sum + lesson.duration, 0);
            const maxDailyMinutes = 7 * 60; // 7 hours maximum

            return totalDuration <= maxDailyMinutes;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Teachers should not exceed seven hours of lessons in a single day.


it('should maintain assessment balance requirements', () => {
      fc.assert(
        fc.property(
          fc.array(domainArbitraries.fullLessonPlan, { minLength: 10, maxLength: 20 }),
          (unitLessons) => {
            // Invariant: Assessment should be balanced across a unit
            const assessmentCounts = new Map<string, number>();

            unitLessons.forEach((lesson) => {
              const type = lesson.assessmentType;
              assessmentCounts.set(type, (assessmentCounts.get(type) || 0) + 1);
            });

            const formativeCount = assessmentCounts.get('formative') || 0;
            const summativeCount = assessmentCounts.get('summative') || 0;
            const total = formativeCount + summativeCount;

            if (total === 0) return true; // No assessments

            const formativeRatio = formativeCount / total;

            // Should have more formative than summative assessments
            return formativeRatio >= 0.6;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: The property ensures that within a unit of lessons, the ratio of formative assessments is at least 60% if any assessments are present.


it('should enforce grade-appropriate content complexity', () => {
      fc.assert(
        fc.property(domainArbitraries.fullLessonPlan, (lessonPlan) => {
          // Invariant: Content complexity should match grade level
          const { grade, action } = lessonPlan;

          // Simple complexity heuristic based on text length and vocabulary
          const words = action.split(/\s+/);
          const averageWordLength =
            words.reduce((sum, word) => sum + word.length, 0) / words.length;

          if (grade <= 3) {
            return averageWordLength <= 6; // Simpler vocabulary
          } else if (grade <= 6) {
            return averageWordLength <= 8; // Moderate vocabulary
          } else {
            return averageWordLength <= 10; // More complex vocabulary
          }
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Content complexity in lesson plans should correspond to the appropriate grade level based on average word length.


it('Drops fudge dice', () => {
    fc.assert(
      fc.property(
        // count & drop: these are dependent
        // we shouldn't be testing if we can drop more than the count - that should be an error
        fc
          .integer({ min: 1, max: 1000000 })
          .chain((count) => fc.tuple(fc.constant(count), fc.nat({ max: count }))),
        // drop mode
        fc.boolean(),
        (countDrop, lowHigh) => {
          const dropGen = new Constant(countDrop[1]);
          const baseDice = new FudgeDiceGroup(countDrop[0]);
          const drop = new Drop(baseDice, dropGen, lowHigh ? KeepDropMode.Low : KeepDropMode.High);
          expect(drop.currentCount).toBe(baseDice.currentCount - dropGen.value());
        },
      ),
    );
  })

Summary: Dropping a specific number of fudge dice should result in the `currentCount` reflecting the correct number of dice removed from the original group.


it('generates stat blocks as expected', () => {
    fc.assert(
      fc.property(fc.integer(), fc.integer(), (valA, valB) => {
        const termA = new Constant(valA);
        const termB = new Constant(valB);
        const combination = new Add(termA, termB);
        expect(combination.statProps.min).toBe(valA + valB);
        expect(combination.statProps.max).toBe(valA + valB);
      }),
    );
  })

Summary: Adding two constant terms results in a `statProps` object where both `min` and `max` are equal to the sum of the two values.


it('should maintain timestamp consistency', () => {
      fc.assert(
        fc.property(
          fc.record({
            createdAt: fc.date({ min: new Date('2020-01-01') }),
            updatedAt: fc.date({ min: new Date('2020-01-01') }),
          }),
          (timestamps) => {
            // Invariant: Updated timestamp should not precede created timestamp
            return timestamps.updatedAt >= timestamps.createdAt;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: The property ensures that the `updatedAt` timestamp does not precede the `createdAt` timestamp.


it('should maintain enumeration value consistency', () => {
      fc.assert(
        fc.property(
          fc.record({
            assessmentType: domainArbitraries.assessmentType,
            achievementLevel: domainArbitraries.achievementLevel,
            userRole: domainArbitraries.userRole,
          }),
          (enums) => {
            // Invariant: Enumeration values should be from valid sets
            const validAssessmentTypes = ['diagnostic', 'formative', 'summative'];
            const validAchievementLevels = ['Level 1', 'Level 2', 'Level 3', 'Level 4'];
            const validUserRoles = ['teacher', 'administrator', 'substitute'];

            return (
              validAssessmentTypes.includes(enums.assessmentType) &&
              validAchievementLevels.includes(enums.achievementLevel) &&
              validUserRoles.includes(enums.userRole)
            );
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Enumeration values for `assessmentType`, `achievementLevel`, and `userRole` should belong to specified valid sets.


it('should maintain data integrity through JSON serialization', () => {
      fc.assert(
        fc.property(domainArbitraries.fullCurriculumExpectation, (expectation) => {
          // Invariant: Data should survive JSON roundtrip
          const serialized = JSON.stringify(expectation);
          const deserialized = JSON.parse(serialized);

          return (
            expectation.id === deserialized.id &&
            expectation.code === deserialized.code &&
            expectation.grade === deserialized.grade &&
            expectation.subject === deserialized.subject
          );
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Ensures data integrity of `expectation` objects is maintained through JSON serialization and deserialization, verifying `id`, `code`, `grade`, and `subject` remain unchanged.


it('should handle date serialization correctly', () => {
      fc.assert(
        fc.property(domainArbitraries.fullLessonPlan, (lessonPlan) => {
          // Invariant: Dates should serialize/deserialize correctly
          const serialized = JSON.stringify({
            ...lessonPlan,
            date: lessonPlan.date.toISOString(),
          });

          const deserialized = JSON.parse(serialized);
          const reconstructedDate = new Date(deserialized.date);

          return reconstructedDate.getTime() === lessonPlan.date.getTime();
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Dates should serialize and deserialize without altering the original timestamp.


it('should maintain reasonable data sizes', () => {
      fc.assert(
        fc.property(domainArbitraries.fullLessonPlan, (lessonPlan) => {
          // Invariant: Data structures should not exceed reasonable sizes
          const serialized = JSON.stringify(lessonPlan);
          const sizeInBytes = new Blob([serialized]).size;

          // Should not exceed 10KB per lesson plan
          return sizeInBytes <= 10 * 1024;
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: The data structure for a lesson plan should not exceed 10KB when serialized.


it('should validate input data constraints', () => {
      fc.assert(
        fc.property(
          fc.record({
            userInput: fc.string({ minLength: 0, maxLength: 10000 }),
            fieldType: fc.constantFrom('title', 'description', 'notes', 'content'),
          }),
          (input) => {
            // Invariant: User input should be validated and sanitized
            const validateInput = (text: string, type: string): boolean => {
              // Basic validation rules
              const maxLengths = {
                title: 200,
                description: 2000,
                notes: 5000,
                content: 10000,
              };

              const maxLength = maxLengths[type as keyof typeof maxLengths] || 1000;

              // Should not exceed length limits
              if (text.length > maxLength) return false;

              // Should not contain obviously malicious patterns (simplified)
              const suspiciousPatterns = ['<script', 'javascript:', 'data:text/html', 'vbscript:'];

              const lowerText = text.toLowerCase();
              const hasSuspiciousContent = suspiciousPatterns.some((pattern) =>
                lowerText.includes(pattern),
              );

              return !hasSuspiciousContent;
            };

            const isValid = validateInput(input.userInput, input.fieldType);

            // Should return a boolean validation result
            return typeof isValid === 'boolean';
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: User input for specified field types should be validated to ensure it doesn't exceed maximum length or contain suspicious patterns, returning a boolean validation result.


it('should maintain valid elementary grade ranges', () => {
      fc.assert(
        fc.property(gradeArbitrary, (grade) => {
          // Property: All grades should be within elementary range (1-8)
          return grade >= 1 && grade <= 8;
        }),
        { numRuns: 100 },
      );
    })

Summary: Grades should be within the elementary range of 1 to 8.


it('should generate diverse curriculum codes', () => {
      fc.assert(
        fc.property(
          fc.array(curriculumCodeArbitrary, { minLength: 10, maxLength: 20 }),
          (codes) => {
            // Property: Should generate reasonably diverse codes
            const uniqueCodes = new Set(codes);
            const diversityRatio = uniqueCodes.size / codes.length;
            return diversityRatio > 0.5; // At least 50% unique
          },
        ),
        { numRuns: 50 },
      );
    })

Summary: Generated curriculum codes should have at least 50% uniqueness.


it('should maintain valid subject-grade combinations', () => {
      fc.assert(
        fc.property(fc.tuple(gradeArbitrary, subjectArbitrary), ([grade, subject]) => {
          // Property: All subject-grade combinations should be valid for elementary
          const validGradeRange = grade >= 1 && grade <= 8;
          const validSubject = [
            'Mathematics',
            'Language Arts',
            'Science',
            'Social Studies',
          ].includes(subject);

          return validGradeRange && validSubject;
        }),
        { numRuns: 100 },
      );
    })

Summary: Subject-grade combinations must be valid, ensuring grades are between 1 and 8 and subjects are within the specified list for elementary education.


it('should maintain curriculum expectation structure', () => {
      fc.assert(
        fc.property(
          fc.record({
            id: fc.uuid(),
            code: curriculumCodeArbitrary,
            description: fc.string({ minLength: 10, maxLength: 200 }),
            grade: gradeArbitrary,
            subject: subjectArbitrary,
          }),
          (expectation) => {
            // Property: All required fields should be present and valid
            const hasValidId = expectation.id.length > 0;
            const hasValidCode = /^[A-E][1-5]\.[1-9]$|^[A-E][1-5]\.10$/.test(expectation.code);
            const hasValidDescription = expectation.description.trim().length >= 10;
            const hasValidGrade = expectation.grade >= 1 && expectation.grade <= 8;
            const hasValidSubject = expectation.subject.length > 0;

            return (
              hasValidId && hasValidCode && hasValidDescription && hasValidGrade && hasValidSubject
            );
          },
        ),
        { numRuns: 50 },
      );
    })

Summary: Curriculum expectations should have a valid structure with a non-empty UUID, a code matching the pattern, a description between 10 and 200 characters, a grade between 1 and 8, and a non-empty subject.


it('should maintain grade ordering properties', () => {
      fc.assert(
        fc.property(fc.tuple(gradeArbitrary, gradeArbitrary), ([grade1, grade2]) => {
          // Property: Grade comparison should be transitive
          if (grade1 < grade2) {
            return grade1 !== grade2 && grade2 > grade1;
          } else if (grade1 > grade2) {
            return grade1 !== grade2 && grade1 > grade2;
          } else {
            return grade1 === grade2;
          }
        }),
        { numRuns: 100 },
      );
    })

Summary: The test checks that the comparison of grades is transitive, ensuring consistent ordering between `grade1` and `grade2`.


it('should handle curriculum code formatting consistently', () => {
      fc.assert(
        fc.property(curriculumCodeArbitrary, (code) => {
          // Property: Code formatting should be consistent
          const upperCased = code.toUpperCase();
          const lowerCased = code.toLowerCase();

          // Original should be uppercase (as generated)
          return code === upperCased && code !== lowerCased;
        }),
        { numRuns: 50 },
      );
    })

Summary: Curriculum codes should be consistently uppercase, ensuring they match their uppercase conversion and differ from their lowercase conversion.


it('should maintain consistent response structure', () => {
      fc.assert(
        fc.property(
          fc.record({
            success: fc.boolean(),
            data: fc.oneof(fc.object(), fc.array(fc.object()), fc.constant(null)),
            error: fc.option(fc.string()),
            timestamp: fc.date().map((d) => d.toISOString()),
            requestId: fc.uuid(),
          }),
          (response) => {
            // Property: API responses should follow consistent structure
            const hasRequiredFields =
              typeof response.success === 'boolean' && response.timestamp && response.requestId;

            // Success responses should have data, error responses should have error message
            const validSuccessResponse = !response.success || response.data !== null;
            const validErrorResponse = response.success || response.error;

            return hasRequiredFields && validSuccessResponse && validErrorResponse;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: API responses should consistently contain boolean `success`, `timestamp`, and `requestId`, with `success` responses having non-null `data`, and non-`success` responses having an `error` message.


it('should validate request payload structure', () => {
      fc.assert(
        fc.property(
          fc.record({
            method: fc.constantFrom('GET', 'POST', 'PUT', 'DELETE', 'PATCH'),
            endpoint: fc.string({ minLength: 1, maxLength: 100 }),
            headers: fc.dictionary(fc.string(), fc.string()),
            body: fc.option(fc.object()),
            query: fc.option(fc.dictionary(fc.string(), fc.string())),
          }),
          (request) => {
            // Property: Requests should have valid structure
            const hasValidMethod = ['GET', 'POST', 'PUT', 'DELETE', 'PATCH'].includes(
              request.method,
            );
            const hasValidEndpoint = request.endpoint.length > 0;
            const hasValidHeaders = typeof request.headers === 'object';

            // GET requests should not have body
            const validGetRequest = request.method !== 'GET' || !request.body;

            // POST/PUT requests should have body for data operations
            const validDataRequest =
              !['POST', 'PUT', 'PATCH'].includes(request.method) || request.body !== null;

            return (
              hasValidMethod &&
              hasValidEndpoint &&
              hasValidHeaders &&
              validGetRequest &&
              validDataRequest
            );
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: The request payload structure must include a valid HTTP method, a non-empty endpoint, valid headers, no body for GET requests, and a body for POST, PUT, or PATCH requests when required.


it('should handle curriculum expectation queries correctly', () => {
      fc.assert(
        fc.property(
          fc.record({
            grade: fc.option(domainArbitraries.grade),
            subject: fc.option(domainArbitraries.subject),
            strand: fc.option(domainArbitraries.curriculumStrand),
            limit: fc.option(fc.integer({ min: 1, max: 100 })),
            offset: fc.option(fc.integer({ min: 0, max: 1000 })),
          }),
          (query) => {
            // Property: Curriculum queries should produce valid filter criteria
            const mockCurriculumAPI = (params: typeof query) => {
              // Simulate API response structure
              const filters: Record<string, any> = {};

              if (params.grade) filters.grade = params.grade;
              if (params.subject) filters.subject = params.subject;
              if (params.strand) filters.strand = params.strand;

              const pagination = {
                limit: Math.min(params.limit || 25, 100),
                offset: Math.max(params.offset || 0, 0),
              };

              return {
                success: true,
                data: {
                  expectations: [], // Would contain actual data
                  filters,
                  pagination,
                  total: 0,
                },
                error: null,
              };
            };

            const response = mockCurriculumAPI(query);

            // Validate response structure and logic
            const hasValidStructure = response.success && response.data;
            const hasValidPagination =
              response.data.pagination.limit <= 100 && response.data.pagination.offset >= 0;

            return hasValidStructure && hasValidPagination;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Curriculum expectation queries should produce API responses with valid filter criteria and pagination limits that do not exceed specified boundaries.


it('should validate curriculum expectation creation', () => {
      fc.assert(
        fc.property(domainArbitraries.fullCurriculumExpectation, (expectation) => {
          // Property: Curriculum creation should validate required fields
          const validateCurriculumExpectation = (data: typeof expectation) => {
            const errors: string[] = [];

            if (!data.code || !/^[A-E][1-5]\.[1-9]|10$/.test(data.code)) {
              errors.push('Invalid curriculum code format');
            }

            if (!data.description || data.description.trim().length === 0) {
              errors.push('Description is required');
            }

            if (!data.strand || data.strand.trim().length === 0) {
              errors.push('Strand is required');
            }

            if (!data.grade || data.grade < 1 || data.grade > 8) {
              errors.push('Grade must be between 1 and 8');
            }

            if (!data.subject || data.subject.trim().length === 0) {
              errors.push('Subject is required');
            }

            return {
              isValid: errors.length === 0,
              errors,
            };
          };

          const validation = validateCurriculumExpectation(expectation);

          // Well-formed expectations should pass validation
          return validation.isValid;
        }),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Curriculum expectation creation should validate that the fields for code, description, strand, grade, and subject meet specified requirements, ensuring well-formed expectations pass validation.


it('should handle lesson plan CRUD operations correctly', () => {
      fc.assert(
        fc.property(
          domainArbitraries.fullLessonPlan,
          fc.constantFrom('CREATE', 'READ', 'UPDATE', 'DELETE'),
          (lessonPlan, operation) => {
            // Property: CRUD operations should follow REST conventions
            const mockLessonPlanAPI = (data: typeof lessonPlan, op: string) => {
              switch (op) {
                case 'CREATE':
                  return {
                    success: true,
                    data: { ...data, id: fc.sample(fc.uuid(), 1)[0] },
                    error: null,
                  };

                case 'READ':
                  return {
                    success: true,
                    data: data,
                    error: null,
                  };

                case 'UPDATE':
                  return {
                    success: true,
                    data: { ...data, updatedAt: new Date() },
                    error: null,
                  };

                case 'DELETE':
                  return {
                    success: true,
                    data: { deleted: true, id: data.id },
                    error: null,
                  };

                default:
                  return {
                    success: false,
                    data: null,
                    error: 'Invalid operation',
                  };
              }
            };

            const response = mockLessonPlanAPI(lessonPlan, operation);

            // Validate operation-specific responses
            if (operation === 'CREATE') {
              return response.success && response.data && response.data.id;
            } else if (operation === 'DELETE') {
              return response.success && response.data && response.data.deleted;
            } else {
              return response.success && response.data;
            }
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Lesson plan CRUD operations return success with expected data formats and handle specific conditions, such as generating an ID on creation and marking as deleted.


it('should validate lesson plan scheduling constraints', () => {
      fc.assert(
        fc.property(
          fc.array(domainArbitraries.fullLessonPlan, { minLength: 2, maxLength: 5 }),
          (lessons) => {
            // Property: API should detect scheduling conflicts
            const detectSchedulingConflicts = (lessonPlans: typeof lessons) => {
              const conflicts: Array<{ lesson1: string; lesson2: string; reason: string }> = [];

              for (let i = 0; i < lessonPlans.length; i++) {
                for (let j = i + 1; j < lessonPlans.length; j++) {
                  const lesson1 = lessonPlans[i];
                  const lesson2 = lessonPlans[j];

                  // Check if same day
                  if (lesson1.date.toDateString() === lesson2.date.toDateString()) {
                    // Calculate end times
                    const end1 = new Date(lesson1.date.getTime() + lesson1.duration * 60 * 1000);
                    const end2 = new Date(lesson2.date.getTime() + lesson2.duration * 60 * 1000);

                    // Check for time overlap
                    if (lesson1.date < end2 && end1 > lesson2.date) {
                      conflicts.push({
                        lesson1: lesson1.id,
                        lesson2: lesson2.id,
                        reason: 'Time overlap',
                      });
                    }
                  }
                }
              }

              return {
                hasConflicts: conflicts.length > 0,
                conflicts,
              };
            };

            const conflictCheck = detectSchedulingConflicts(lessons);

            // Should return valid conflict detection result
            return (
              typeof conflictCheck.hasConflicts === 'boolean' &&
              Array.isArray(conflictCheck.conflicts)
            );
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Validates that the scheduling conflict detection for lesson plans returns a boolean for conflict presence and an array of conflicts.


it('should handle assessment data correctly', () => {
      fc.assert(
        fc.property(
          fc.record({
            lessonId: fc.uuid(),
            assessmentType: domainArbitraries.assessmentType,
            scores: fc.array(
              fc.record({
                expectationId: fc.uuid(),
                score: domainArbitraries.percentage,
                notes: fc.option(fc.string({ maxLength: 500 })),
              }),
              { minLength: 1, maxLength: 5 },
            ),
            completedAt: fc.date(),
          }),
          (assessmentData) => {
            // Property: Assessment API should validate and process scores correctly
            const processAssessmentData = (data: typeof assessmentData) => {
              const validationErrors: string[] = [];

              // Validate lesson reference
              if (!data.lessonId) {
                validationErrors.push('Lesson ID is required');
              }

              // Validate assessment type
              if (!['diagnostic', 'formative', 'summative'].includes(data.assessmentType)) {
                validationErrors.push('Invalid assessment type');
              }

              // Validate scores
              for (const score of data.scores) {
                if (score.score < 0 || score.score > 100) {
                  validationErrors.push(`Invalid score: ${score.score}`);
                }

                if (!score.expectationId) {
                  validationErrors.push('Expectation ID is required for each score');
                }
              }

              // Calculate overall score
              const overallScore =
                data.scores.reduce((sum, s) => sum + s.score, 0) / data.scores.length;

              return {
                isValid: validationErrors.length === 0,
                errors: validationErrors,
                data:
                  validationErrors.length === 0
                    ? {
                        ...data,
                        overallScore,
                        processedAt: new Date(),
                      }
                    : null,
              };
            };

            const result = processAssessmentData(assessmentData);

            // Valid assessment data should process successfully
            return (
              result.isValid &&
              result.data &&
              result.data.overallScore >= 0 &&
              result.data.overallScore <= 100
            );
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Assessment data should be validated and processed correctly, ensuring valid lesson IDs, assessment types, scores between 0 and 100, and expectation IDs for each score, resulting in a valid overall score calculation between 0 and 100.


it('should handle user permissions correctly', () => {
      fc.assert(
        fc.property(
          domainArbitraries.userRole,
          fc.constantFrom('create', 'read', 'update', 'delete'),
          fc.constantFrom('lesson-plans', 'curriculum', 'assessments', 'users'),
          (userRole, action, resource) => {
            // Property: Permission system should enforce role-based access
            const checkPermissions = (role: string, operation: string, resourceType: string) => {
              const permissions = {
                teacher: {
                  'lesson-plans': ['create', 'read', 'update', 'delete'],
                  curriculum: ['read'],
                  assessments: ['create', 'read', 'update'],
                  users: [],
                },
                administrator: {
                  'lesson-plans': ['create', 'read', 'update', 'delete'],
                  curriculum: ['create', 'read', 'update', 'delete'],
                  assessments: ['create', 'read', 'update', 'delete'],
                  users: ['create', 'read', 'update', 'delete'],
                },
                substitute: {
                  'lesson-plans': ['read'],
                  curriculum: ['read'],
                  assessments: ['read'],
                  users: [],
                },
              };

              const rolePermissions = permissions[role as keyof typeof permissions];
              const resourcePermissions =
                rolePermissions?.[resourceType as keyof typeof rolePermissions] || [];

              return resourcePermissions.includes(operation);
            };

            const hasPermission = checkPermissions(userRole, action, resource);

            // Should return boolean permission result
            return typeof hasPermission === 'boolean';
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: The permission system should correctly enforce role-based access, returning a boolean when checking if a user role can perform an action on a resource.


it('should handle malformed requests gracefully', () => {
      fc.assert(
        fc.property(
          fc.oneof(
            fc.constant(null),
            fc.constant(undefined),
            fc.string(),
            fc.integer(),
            fc.object(),
            fc.array(fc.anything()),
          ),
          (malformedInput) => {
            // Property: API should handle malformed input gracefully
            const handleRequest = (input: unknown) => {
              try {
                // Simulate request validation
                if (input === null || input === undefined) {
                  return {
                    success: false,
                    data: null,
                    error: 'Request body is required',
                  };
                }

                if (typeof input !== 'object' || Array.isArray(input)) {
                  return {
                    success: false,
                    data: null,
                    error: 'Request body must be an object',
                  };
                }

                return {
                  success: true,
                  data: input,
                  error: null,
                };
              } catch (_error) {
                return {
                  success: false,
                  data: null,
                  error: 'Internal server error',
                };
              }
            };

            const response = handleRequest(malformedInput);

            // Should always return valid response structure
            return (
              typeof response.success === 'boolean' &&
              (response.success ? response.data !== null : response.error !== null)
            );
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: API should handle malformed inputs by returning a valid response structure, indicating success or providing an appropriate error message.


it('should never do more than 7 races', () => {
    fc.assert(
      fc.property(tupleN(fc.nat(), 25), (speeds) => {
        // Arrange
        const compareParticipants = (pa: number, pb: number) => {
          if (speeds[pa] !== speeds[pb]) return speeds[pb] - speeds[pa];
          else return pa - pb;
        };
        const runRace = jest.fn((...participants: RaceParticipants): RaceParticipants => {
          return participants.sort(compareParticipants);
        });

        // Act
        racePodium(runRace);

        // Assert
        expect(runRace.mock.calls.length).toBeLessThanOrEqual(7);
      })
    );
  })

Summary: The test ensures that the `racePodium` function does not perform more than 7 race operations, even when processing an array of 25 natural numbers as speeds.


it('should provide meaningful error messages', () => {
      fc.assert(
        fc.property(
          fc.record({
            field: fc.constantFrom('email', 'password', 'grade', 'duration'),
            value: fc.oneof(fc.string(), fc.integer(), fc.constant(null)),
            validationRule: fc.constantFrom('required', 'format', 'range', 'length'),
          }),
          (validationCase) => {
            // Property: Error messages should be specific and helpful
            const generateErrorMessage = (field: string, value: unknown, rule: string) => {
              switch (rule) {
                case 'required':
                  if (value === null || value === undefined || value === '') {
                    return `${field} is required`;
                  }
                  break;

                case 'format':
                  if (field === 'email' && typeof value === 'string' && !value.includes('@')) {
                    return `${field} must be a valid email address`;
                  }
                  break;

                case 'range':
                  if (field === 'grade' && (typeof value !== 'number' || value < 1 || value > 8)) {
                    return `${field} must be between 1 and 8`;
                  }
                  break;

                case 'length':
                  if (field === 'password' && typeof value === 'string' && value.length < 8) {
                    return `${field} must be at least 8 characters long`;
                  }
                  break;
              }

              return null; // No error
            };

            const errorMessage = generateErrorMessage(
              validationCase.field,
              validationCase.value,
              validationCase.validationRule,
            );

            // Error message should be string or null
            return errorMessage === null || typeof errorMessage === 'string';
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Error messages generated based on validation rules for fields should either be specific strings or null, ensuring meaningful feedback.


it('should enforce rate limits correctly', () => {
      fc.assert(
        fc.property(
          fc.integer({ min: 1, max: 100 }),
          fc.integer({ min: 1, max: 3600 }),
          fc.array(fc.integer({ min: 0, max: 3600 }), { minLength: 10, maxLength: 50 }),
          (maxRequests, timeWindowSeconds, requestTimes) => {
            // Property: Rate limiting should track requests within time windows
            const checkRateLimit = (max: number, window: number, times: number[]) => {
              const sortedTimes = [...times].sort((a, b) => a - b);
              const violations: number[] = [];

              for (let i = 0; i < sortedTimes.length; i++) {
                const currentTime = sortedTimes[i];
                const windowStart = currentTime - window;

                // Count requests in the current window
                const requestsInWindow = sortedTimes.filter(
                  (time) => time >= windowStart && time <= currentTime,
                ).length;

                if (requestsInWindow > max) {
                  violations.push(currentTime);
                }
              }

              return {
                violations: violations.length,
                wouldBlock: violations.length > 0,
              };
            };

            const rateLimitResult = checkRateLimit(maxRequests, timeWindowSeconds, requestTimes);

            // Should return valid rate limit analysis
            return (
              typeof rateLimitResult.violations === 'number' &&
              typeof rateLimitResult.wouldBlock === 'boolean'
            );
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: The rate limiting function tracks and evaluates request counts within specified time windows, ensuring the result includes a number of violations and a boolean indicating potential blocking.


it('should handle pagination consistently', () => {
      fc.assert(
        fc.property(
          fc.integer({ min: 0, max: 1000 }),
          fc.integer({ min: 1, max: 100 }),
          fc.integer({ min: 0, max: 10000 }),
          (offset, limit, totalItems) => {
            // Property: Pagination should calculate pages correctly
            const calculatePagination = (off: number, lim: number, total: number) => {
              const validatedOffset = Math.max(0, off);
              const validatedLimit = Math.min(Math.max(1, lim), 100);

              const totalPages = Math.ceil(total / validatedLimit);
              const currentPage = Math.floor(validatedOffset / validatedLimit) + 1;
              const hasNextPage = validatedOffset + validatedLimit < total;
              const hasPrevPage = validatedOffset > 0;

              return {
                offset: validatedOffset,
                limit: validatedLimit,
                total,
                totalPages,
                currentPage,
                hasNextPage,
                hasPrevPage,
              };
            };

            const pagination = calculatePagination(offset, limit, totalItems);

            // Validate pagination logic
            const validCurrentPage =
              pagination.currentPage >= 1 &&
              pagination.currentPage <= Math.max(1, pagination.totalPages);
            const validNextPage =
              pagination.hasNextPage === pagination.offset + pagination.limit < pagination.total;
            const validPrevPage = pagination.hasPrevPage === pagination.offset > 0;

            return validCurrentPage && validNextPage && validPrevPage;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: Pagination should accurately calculate total pages, current page, and the presence of next and previous pages based on given offset, limit, and total items.


it('should handle reasonable payload sizes', () => {
      fc.assert(
        fc.property(
          fc.array(domainArbitraries.fullLessonPlan, { minLength: 1, maxLength: 100 }),
          (lessonPlans) => {
            // Property: API should handle reasonable batch sizes
            const estimatePayloadSize = (data: typeof lessonPlans) => {
              const serialized = JSON.stringify(data);
              return new Blob([serialized]).size;
            };

            const payloadSize = estimatePayloadSize(lessonPlans);
            const maxReasonableSize = 5 * 1024 * 1024; // 5MB

            // Large payloads should be rejected or paginated
            const shouldPaginate = payloadSize > maxReasonableSize;
            const isReasonableSize = payloadSize <= maxReasonableSize;

            // Either size is reasonable or we know it should be paginated
            return isReasonableSize || shouldPaginate;
          },
        ),
        getPropertyTestConfig('fast'),
      );
    })

Summary: The API should either handle payloads up to a reasonable size limit or require pagination for larger payloads.


it("should correctly set and retrieve items", () => {
    fc.assert(
      fc.property(fc.string(), fc.string(), (key, value) => {
        storage.setItem(key, value);
        const mockData: DataStore = { [v2UnescapedStoreKey(key)]: value };
        storage.receive(mockData);
        if (value === "") {
          expect(storage.getItem(key)).toBeNull();
        } else {
          expect(storage.getItem(key)).toEqual(value);
        }
      }),
      { numRuns: 100 },
    );
  })

Summary: Setting an item with a key-value pair should allow retrieving the same value unless the value is an empty string, in which case retrieval should return null.


it("should return null for non-existing items", () => {
    fc.assert(
      fc.property(fc.string(), key => {
        expect(storage.getItem(key)).toBeNull();
      }),
      { numRuns: 100 },
    );
  })

Summary: `storage.getItem` returns null for keys that do not exist.


it("should correctly remove items", () => {
    fc.assert(
      fc.property(fc.string(), fc.string(), (key, value) => {
        storage.setItem(key, value);
        storage.removeItem(key);
        expect(storage.getItem(key)).toBeNull();
      }),
      { numRuns: 100 },
    );
  })

Summary: Removing an item from storage results in `getItem` returning null for that key.


it("should ensure all set items are v2-coded internally", () => {
    fc.assert(
      fc.property(fc.string(), fc.string(), (key, value) => {
        storage.setItem(key, value);
        const mockData: DataStore = { [v2UnescapedStoreKey(key)]: value };
        storage.receive(mockData);
        if (value === "") {
          expect(storage.getItem(key)).toBeNull();
        } else {
          expect(storage.getItem(key)).toEqual(value);
        }
      }),
      { numRuns: 100 },
    );
  })

Summary: All items set in storage should be represented internally using v2-coded keys and retrieved accurately, with empty values resulting in null.


it("arrayToHex -> hexToArray", () => {
        fc.assert(
            fc.property(fc.uint8Array({ minLength: 2 }), data => {
                fc.pre(data.length % 2 == 0);
                assert.deepEqual(hexToArray(arrayToHex(data)), data);
            })
        );
    })

Summary: Converting a `uint8Array` to a hex string and back to an array should return the original array.


it("parse local path", () => {
        fc.assert(
            fc.property(fc.string(), string => {
                const typed = `local:${string}`;
                assert.deepEqual(parseTypedPath(typed), ["local", string]);
            })
        );
    })

Summary: `parseTypedPath` splits a string with a "local:" prefix into an array with "local" and the remaining string.


it("parse unqualified path", () => {
        fc.assert(
            fc.property(fc.string(), string => {
                fc.pre(!string.includes(":"));
                assert.deepEqual(parseTypedPath(string), [undefined, string]);
            })
        );
    })

Summary: `parseTypedPath` returns an array with `undefined` and the original string if the string does not contain a colon.


it("should preserve the state when zoom in and zoom out on the same position", () => {
      const precision = 1 / 100;
      const maxZooms = 10;
      const zoomSpeed = 1.1;
      const arbitraryState = fc
        .integer(1, 1000)
        .chain((ratio) =>
          fc.tuple(fc.constant(ratio), fc.float(0, 1 - 1 / ratio))
        )
        .chain(([ratio, offset]) =>
          fc.tuple(
            fc.constant(ratio),
            fc.constant(offset),
            fc.float(offset, offset + 1 / ratio),
            fc.nat(maxZooms)
          )
        );
      fc.assert(
        fc.property(
          arbitraryState,
          ([ratio, offset, mousePosition, numberOfZooms]) => {
            const zoomIns = _.range(numberOfZooms).map(() => ({
              mousePosition,
              zoomDirection: ZoomDirection.IN,
              zoomSpeed,
            }));

            const zoomOuts = _.range(numberOfZooms).map(() => ({
              mousePosition,
              zoomDirection: ZoomDirection.OUT,
              zoomSpeed,
            }));

            const zoomInsState = zoomIns.reduce(zoomReducer, {
              offset,
              ratio,
            });

            const finalState = zoomOuts.reduce(zoomReducer, zoomInsState);

            const isRatioOk =
              ratio - precision < finalState.ratio &&
              ratio + precision > finalState.ratio;
            const isOffsetOk =
              offset - precision < finalState.offset &&
              offset + precision > finalState.offset;

            return isRatioOk && isOffsetOk;
          }
        )
      );
    })

Summary: Zooming in and then out on the same position should preserve the initial ratio and offset state within a defined precision.


it("should create a new object", () => {
      fc.assert(
        fc.property(fc.object(), (obj) => {
          expect(copy(obj)).not.toBe(obj);
        })
      );
    })

Summary: The `copy` function should return a new object that is not the same instance as the input object.


it("should correctly format dates", () => {
      fc.assert(
        fc.property(
          fc.integer(1, 28),
          fc.integer(0, 11),
          fc.integer(1971, 2071),
          (day, month, year) => {
            const date = Date.UTC(year, month, day);
            const paddedDay = `0${day}`.slice(-2);
            const paddedMonth = `0${month + 1}`.slice(-2);
            return (
              epochToFormattedUtcDateString(date) ===
              `${paddedDay}/${paddedMonth}/${year}`
            );
          }
        )
      );
    })

Summary: `epochToFormattedUtcDateString` should convert a date into a formatted string "DD/MM/YYYY" using given day, month, and year.


it("(fromRgba . toRgba) a", () => {
    fc.assert(
      fc.property(arbitraryRgba, (color) =>
        equal(color, fromRgba(toRgba(color)))
      )
    );
  })

Summary: Converting an RGBA color to a string and back to RGBA should yield the original color.


it("should always succeed", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.anything(), (input) => {
          expect(castUnknown(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: `castUnknown` should return an object with the status "success" and the original input as the value when given any input.


it("should always fail", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.anything(), (input) => {
          expect(castNever(input)).toStrictEqual({
            status: "failure",
            expected: "never",
            actual: input
          });
        })
      );
    })

Summary: `castNever` should return an object indicating a failure with the expected value "never" and the actual input for any given input.


it("should successfully cast strings", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.string(), (input) => {
          expect(castString(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: `castString` returns an object with the properties `status: "success"`, `value` equal to the input string, and an empty `values` array for any string input.


it("should fail to cast non-strings", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.anything().filter((input) => typeof input !== "string"),
          (input) => {
            expect(castString(input)).toStrictEqual({
              status: "failure",
              expected: "string",
              actual: input
            });
          }
        )
      );
    })

Summary: `castString` returns a failure status when attempting to cast non-string inputs.


it("should successfully cast numbers", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.double(), (input) => {
          expect(castNumber(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: The function `castNumber` should return an object with `status` as "success", `value` as the input number, and an empty `values` array for double inputs.


it('should never request any changes when moving a string to itself', () => {
    fc.assert(
      fc.property(fc.fullUnicodeString(), (value) => {
        // Arrange / Act
        const numChanges = minimalNumberOfChangesToBeOther(value, value);

        // Assert
        expect(numChanges).toBe(0);
      })
    );
  })

Summary: The property tests that transforming a string into itself requires zero changes.


it("should fail to cast non-numbers", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.anything().filter((input) => typeof input !== "number"),
          (input) => {
            expect(castNumber(input)).toStrictEqual({
              status: "failure",
              expected: "number",
              actual: input
            });
          }
        )
      );
    })

Summary: `castNumber` returns a failure status with expected type "number" for non-numeric inputs.


it("should successfully cast bigints", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.bigInt(), (input) => {
          expect(castBigInt(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: The `castBigInt` function casts input bigints successfully, returning an object with a status of "success" and the original input value.


it("should fail to cast non-bigints", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.anything().filter((input) => typeof input !== "bigint"),
          (input) => {
            expect(castBigInt(input)).toStrictEqual({
              status: "failure",
              expected: "bigint",
              actual: input
            });
          }
        )
      );
    })

Summary: Verifies that casting non-bigint inputs with `castBigInt` results in a failure status with details of the expected and actual types.


it("should successfully cast booleans", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.boolean(), (input) => {
          expect(castBoolean(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: The function `castBoolean` should return an object with a status of "success," the original boolean value, and an empty array for any boolean input.


it("should fail to cast non-symbols", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.anything().filter((input) => typeof input !== "symbol"),
          (input) => {
            expect(castSymbol(input)).toStrictEqual({
              status: "failure",
              expected: "symbol",
              actual: input
            });
          }
        )
      );
    })

Summary: `castSymbol` returns a failure status when given a non-symbol input, specifying the expected and actual types.


it("should successfully cast number arrays", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.array(fc.double()), (input) => {
          expect(castNums(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: `castNums` returns an object with a "success" status and original number array unchanged.


it("should fail to cast non-arrays", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.anything().filter((input) => !Array.isArray(input)),
          (input) => {
            expect(castNums(input)).toStrictEqual({
              status: "failure",
              expected: "array",
              actual: input
            });
          }
        )
      );
    })

Summary: `castNums` should return a failure status with expected type "array" when given non-array inputs.


it("should successfully cast triples", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.tuple(fc.string(), fc.double(), fc.boolean()),
          (input) => {
            expect(castTriple(input)).toStrictEqual({
              status: "success",
              value: input,
              values: []
            });
          }
        )
      );
    })

Summary: The `castTriple` function should return an object with a "success" status and the input as the value for tuples of a string, double, and boolean.


it("should fail to cast invalid triples", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.tuple(
            fc.anything().filter((input) => typeof input !== "string"),
            fc.anything().filter((input) => typeof input !== "number"),
            fc.anything().filter((input) => typeof input !== "boolean")
          ),
          (input) => {
            const [first, second, third] = input;
            expect(castTriple(input)).toStrictEqual({
              status: "failure",
              expected: "tuple",
              length: 3,
              items: [
                { status: "failure", expected: "string", actual: first },
                { status: "failure", expected: "number", actual: second },
                { status: "failure", expected: "boolean", actual: third }
              ],
              actual: input
            });
          }
        )
      );
    })

Summary: `castTriple` returns a failure status for non-string, non-number, and non-boolean elements in a tuple.


it("should fail to cast non-triples", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.tuple(fc.string(), fc.double()), (input) => {
          expect(castTriple(input)).toStrictEqual({
            status: "failure",
            expected: "tuple",
            length: 3,
            actual: input
          });
        })
      );
    })

Summary: `castTriple` returns an error status when attempting to cast tuples that are not of length three.


it("should fail to cast non-arrays", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.anything().filter((input) => !Array.isArray(input)),
          (input) => {
            expect(castTriple(input)).toStrictEqual({
              status: "failure",
              expected: "tuple",
              length: 3,
              actual: input
            });
          }
        )
      );
    })

Summary: `castTriple` returns a failure object when attempting to cast non-array inputs.


it("should successfully cast numeric records", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.dictionary(fc.string(), fc.double()), (input) => {
          expect(castNumericRecord(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: The `castNumericRecord` function should return a success status with the input record and an empty values array for numeric records.


it("should fail to cast non-numeric records", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.dictionary(
            fc.string(),
            fc.anything().filter((input) => typeof input !== "number"),
            { minKeys: 1 }
          ),
          (input) => {
            expect(castNumericRecord(input)).toStrictEqual({
              status: "failure",
              expected: "record",
              properties: Object.fromEntries(
                Object.entries(input).map(([key, actual]) => [
                  key,
                  { status: "failure", expected: "number", actual }
                ])
              ),
              actual: input
            });
          }
        )
      );
    })

Summary: `castNumericRecord` returns a failure status when attempting to cast records containing non-numeric values.


it("should fail to cast non-records", () => {
      expect.assertions(101);
      const property = (input: unknown) => {
        expect(castNumericRecord(input)).toStrictEqual({
          status: "failure",
          expected: "record",
          actual: input
        });
      };
      fc.assert(
        fc.property(
          fc.anything().filter((input) => typeof input !== "object"),
          property
        )
      );
      // eslint-disable-next-line unicorn/no-null -- testing null
      property(null);
    })

Summary: `castNumericRecord` returns a status of "failure" for non-object inputs, including `null`, with an expectation of "record".


it("should successfully cast objects", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.record({ foo: fc.string(), bar: fc.double(), baz: fc.boolean() }),
          (input) => {
            expect(castObject(input)).toStrictEqual({
              status: "success",
              value: input,
              values: []
            });
          }
        )
      );
    })

Summary: `castObject` returns an object with `"status": "success"`, echoing the input when given records with specific types for properties.


it('should print Fizz whenever divisible by 3', () => {
    fc.assert(
      fc.property(
        fc.nat().map((n) => n * 3),
        (n) => {
          expect(fizzbuzz(n)).toContain('Fizz');
        }
      )
    );
  })

Summary: `fizzbuzz` includes "Fizz" in its output for numbers divisible by 3.


it('should not print Fizz when not divisible by 3', () => {
    fc.assert(
      fc.property(
        fc.oneof(
          fc.nat().map((n) => n * 3 + 1),
          fc.nat().map((n) => n * 3 + 2)
        ),
        (n) => {
          expect(fizzbuzz(n)).not.toContain('Fizz');
        }
      )
    );
  })

Summary: When a number is not divisible by 3, `fizzbuzz` should not include "Fizz" in its output.


it('should be able to decompose a product of two numbers', () => {
    fc.assert(
      fc.property(fc.integer(2, MAX_INPUT), fc.integer(2, MAX_INPUT), (a, b) => {
        const n = a * b;
        const factors = decomposeIntoPrimes(n);
        return factors.length >= 2;
      })
    );
  })

Summary: Decomposing the product of two integers into prime factors should result in at least two factors.


it("should fail to cast invalid objects", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.record({
            foo: fc.anything().filter((input) => typeof input !== "string"),
            bar: fc.anything().filter((input) => typeof input !== "number")
          }),
          (input) => {
            const { foo, bar } = input;
            expect(castObject(input)).toStrictEqual({
              status: "failure",
              expected: "object",
              properties: {
                foo: { status: "failure", expected: "string", actual: foo },
                bar: { status: "failure", expected: "number", actual: bar },
                baz: {
                  status: "failure",
                  expected: "boolean",
                  actual: undefined
                }
              },
              actual: input
            });
          }
        )
      );
    })

Summary: Casting an object with non-string `foo` or non-number `bar` should result in a failure report detailing the expected and actual types, including a missing `baz` field.


it("should successfully cast numbers", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.double(), (input) => {
          expect(castNullableNumber(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: `castNullableNumber` successfully casts doubles to an object with a status of "success" and includes the input value in the output.


it("should fail to cast non-numbers and non-null", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc
            .anything()
            .filter((input) => typeof input !== "number")
            .filter((input) => input !== null),
          (input) => {
            expect(castNullableNumber(input)).toStrictEqual({
              status: "failure",
              expected: "union",
              variants: [
                { status: "failure", expected: "number", actual: input },
                { status: "failure", expected: "null", actual: input }
              ]
            });
          }
        )
      );
    })

Summary: `castNullableNumber` should return a failure status when attempting to cast inputs that are neither numbers nor null.


it("should successfully cast numbers", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.double(), (input) => {
          expect(castOptionalNumber(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: `castOptionalNumber` successfully casts doubles to an object with `status: "success"`, `value` as the input, and an empty `values` array.


it("should fail to cast non-numbers and non-undefined", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc
            .anything()
            .filter((input) => typeof input !== "number")
            .filter((input) => typeof input !== "undefined"),
          (input) => {
            expect(castOptionalNumber(input)).toStrictEqual({
              status: "failure",
              expected: "union",
              variants: [
                { status: "failure", expected: "number", actual: input },
                { status: "failure", expected: "undefined", actual: input }
              ]
            });
          }
        )
      );
    })

Summary: `castOptionalNumber` should return a failure status when attempting to cast any input that is neither a number nor undefined.


it("should successfully cast bar", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.record({ bar: fc.double() }), (input) => {
          expect(castFooBar(input)).toStrictEqual({
            status: "success",
            value: input,
            values: []
          });
        })
      );
    })

Summary: `castFooBar` should return an object with a status of "success", the input value, and an empty array when given a record with a double value under the key "bar".


it("should fail to cast neither foo nor bar", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.record({ baz: fc.boolean() }), (input) => {
          expect(castFooBar(input)).toStrictEqual({
            status: "failure",
            expected: "intersection",
            results: [
              {
                status: "failure",
                expected: "object",
                properties: {
                  foo: {
                    status: "failure",
                    expected: "string",
                    actual: undefined
                  }
                },
                actual: input
              },
              {
                status: "failure",
                expected: "object",
                properties: {
                  bar: {
                    status: "failure",
                    expected: "number",
                    actual: undefined
                  }
                },
                actual: input
              }
            ]
          });
        })
      );
    })

Summary: The function `castFooBar` returns a failure status with expected types for both "foo" and "bar" when given an input record containing only a boolean "baz" property.


it('should be able to find back the original message', () => {
    fc.assert(
      fc.property(
        fc.set(wordArb, { minLength: 1 }).chain((words) =>
          fc.record({
            words: fc.constant(words),
            originalMessage: fc.array(fc.constantFrom(...words)).map((items) => items.join(' ')),
          })
        ),
        ({ words, originalMessage }) => {
          const spacelessMessage = originalMessage.replace(/\s/g, '');
          const combinations = respace(spacelessMessage, words);
          expect(combinations).toContain(originalMessage);
        }
      )
    );
  })

Summary: `respace` should reconstruct the original message from a spaceless string using a given set of words.


it('should only return messages with spaceless version being the passed message', () => {
    fc.assert(
      fc.property(
        fc.set(wordArb, { minLength: 1 }).chain((words) =>
          fc.record({
            words: fc.shuffledSubarray(words), // we potentially remove words from the dictionary to cover no match case
            originalMessage: fc.array(fc.constantFrom(...words)).map((items) => items.join(' ')),
          })
        ),
        ({ words, originalMessage }) => {
          const spacelessMessage = originalMessage.replace(/\s/g, '');
          const combinations = respace(spacelessMessage, words);
          for (const combination of combinations) {
            expect(combination.replace(/\s/g, '')).toBe(spacelessMessage);
          }
        }
      )
    );
  })

Summary: When respacing a message, all resulting combinations should transform back to the original spaceless message when spaces are removed.


it("should always succeed with a constant answer", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(fc.anything(), (input) => {
          expect(castAnswer(input)).toStrictEqual({
            status: "success",
            value: answer,
            values: []
          });
        })
      );
    })

Summary: The function `castAnswer` always returns an object with a constant structure, `{ status: "success", value: answer, values: [] }`, regardless of the input.


it("should successfully cast recursive data structures", () => {
      expect.assertions(100);
      fc.assert(
        fc.property(
          fc.letrec<{ list: List<number>; cons: Cons<number> }>((tie) => ({
            list: fc.option(tie("cons")),
            cons: fc.record({ head: fc.double(), tail: tie("list") })
          })).list,
          (input) => {
            expect(castNums(input)).toStrictEqual({
              status: "success",
              value: input,
              values: []
            });
          }
        )
      );
    })

Summary: Casts recursive data structures of lists and cons cells to verify successful casting with expected output structure.


it('should build an ExecutableQuery always returning the specified value', () => {
      return fc.assert(
        fc.asyncProperty(fc.anything(), async (a) => {
          const query = ExecutableQuery.of(a);

          const result = await query.run(fakeClient);
          expect(result).toStrictEqual(a);
        })
      );
    })

Summary: `ExecutableQuery.of` creates a query that consistently returns the specified value when run, matching the input.


it('should detect a substring when there is one', () => {
    fc.assert(
      fc.property(fc.string(), fc.string(), fc.string(), (a, b, c) => {
        const searchString = b;
        const text = `${a}${b}${c}`;
        expect(lastIndexOf(searchString, text)).not.toBe(-1);
      })
    );
  })

Summary: `lastIndexOf` should return a non-negative index when a substring is present in a concatenated string.


it('should return the start index of the substring when there is one', () => {
    fc.assert(
      fc.property(fc.string(), fc.string(), fc.string(), (a, b, c) => {
        const searchString = b;
        const text = `${a}${b}${c}`;
        const index = lastIndexOf(searchString, text);
        expect(text.substr(index, searchString.length)).toBe(searchString);
      })
    );
  })

Summary: `lastIndexOf` returns the starting index of a substring within a text, ensuring the extracted portion matches the substring.


it('should return the last possible index of the substring when there is one', () => {
    fc.assert(
      fc.property(fc.string(), fc.string({ minLength: 1 }), fc.string(), (a, b, c) => {
        const searchString = b;
        const text = `${a}${b}${c}`;
        const textBis = text.substring(lastIndexOf(searchString, text) + 1);
        expect(lastIndexOf(searchString, textBis)).toBe(-1);
      })
    );
  })

Summary: The last occurrence of a substring in a composed string should not be found in the remaining substring that follows it.


it('should respect composition', () => {
      return fc.assert(
        fc.asyncProperty(
          arbExecutableQuery(fc.anything()),
          fc.func(fc.anything()),
          fc.func(fc.anything()),
          async (query, fn, fn2) => {
            const result = await query.map(fn).map(fn2).run(fakeClient);
            const expected = await query.map((x) => fn2(fn(x))).run(fakeClient);
            expect(result).toStrictEqual(expected);
          }
        )
      );
    })

Summary: The composition of mapped functions on an `ExecutableQuery` should produce the same result as composing the functions before mapping, then running with `fakeClient`.


it('should respect right identity', () => {
      return fc.assert(
        fc.asyncProperty(arbExecutableQuery(fc.anything()), async (query) => {
          const result = await query.chain((x) => ExecutableQuery.of(x)).run(fakeClient);
          const expected = await query.run(fakeClient);
          expect(result).toStrictEqual(expected);
        })
      );
    })

Summary: An `ExecutableQuery` applied with the right identity operation should yield the same result when executed, compared to executing the original query.


test("The random value should be comprised between min and max boundaries", () => {
    fc.assert(
      fc.property(fc.nat(), fc.nat(), (min, max) => {
        fc.pre(min <= max);
        const result = random(Math.random)({ min, max });
        return min <= result && result <= max;
      }),
    );
  })

Summary: The random value generated should be between the specified minimum and maximum boundaries.


it("never throws", () => {
			fc.assert(
				fc.property(fc.string(), x => {
					f(x)
				}),
			)
		})

Summary: Function `f` should not throw an error for any string input.


it('should respect left identity', () => {
      return fc.assert(
        fc.asyncProperty(fc.anything(), fc.func(arbExecutableQuery(fc.anything())), async (a, fn) => {
          const result = await ExecutableQuery.of(a).chain(fn).run(fakeClient);
          const expected = await fn(a).run(fakeClient);
          expect(result).toStrictEqual(expected);
        })
      );
    })

Summary: `ExecutableQuery.of(a).chain(fn).run(fakeClient)` should produce the same result as `fn(a).run(fakeClient)` for any input and function.


it("returns a prefixed string for non-empty params", () => {
			expect(f(new URLSearchParams("a=b"))).toBe("?a=b")

			fc.assert(
				fc.property(arb.filter(not(isEmpty)), xs => expect(f(xs)[0]).toBe("?")),
			)
		})

Summary: The function `f` returns a string prefixed with "?" when `URLSearchParams` is non-empty.


it("never throws", () => {
			fc.assert(
				fc.property(fc.dictionary(fc.string(), fc.array(fc.string())), x => {
					f(x)
				}),
			)
		})

Summary: The function `f` is tested to ensure it does not throw an exception for any dictionary of strings to arrays of strings.


it('should respect composition', () => {
      return fc.assert(
        fc.asyncProperty(
          arbExecutableQuery(fc.anything()),
          fc.func(arbExecutableQuery(fc.anything())),
          fc.func(arbExecutableQuery(fc.anything())),
          async (query, fn, fn2) => {
            const result = await query.chain(fn).chain(fn2).run(fakeClient);
            const expected = await query.chain((x) => fn(x).chain(fn2)).run(fakeClient);
            expect(result).toStrictEqual(expected);
          }
        )
      );
    })

Summary: Composition of `ExecutableQuery` operations should produce consistent results, whether chaining functions sequentially or nesting them.


it('should get user using id from create user', async () => {
    await fc.assert(
      fc.asyncProperty(accountCreateRequestDtoArbitrary, async (requestDto) => {
        const { id } = await accountController.create(requestDto);

        const responseDto = await accountController.findById(id);

        expect(responseDto.id).toEqual(id);
        expect(responseDto.name).toEqual(requestDto.name);
        expect(responseDto.balance).toEqual(0);
      }),
    );
  })

Summary: Creating a user should return an ID that can be used to retrieve the user with matching name and an initial balance of zero.


it('should final amount is 0 from +- amount transfers', async () => {
    await fc.assert(
      fc.asyncProperty(
        accountCreateRequestDtoArbitrary,
        fc.array(fc.nat()),
        async (requestDto, amounts) => {
          const { id } = await accountController.create(requestDto);

          let userDto = await accountController.findById(id);

          expect(userDto.id).toEqual(id);
          expect(userDto.name).toEqual(requestDto.name);
          expect(userDto.balance).toEqual(0);
          expect(userDto.rawBalance).toEqual(0);

          await Promise.allSettled(
            amounts
              .flatMap((e) =>
                [e, e].map(
                  (amount, idx) =>
                    ({
                      type: [TransferType.Deposit, TransferType.Withdrawal][
                        idx
                      ],
                      accountId: id,
                      amount,
                    }) as TransferCreateRequestDto,
                ),
              )
              .map((e) => accountController.transfer(id, e)),
          );

          userDto = await accountController.findById(id);

          expect(userDto.id).toEqual(id);
          expect(userDto.name).toEqual(requestDto.name);
          expect(userDto.balance).toEqual(0);
          expect(userDto.rawBalance).toEqual(0);
        },
      ),
    );
  }, 500000)

Summary: The test ensures that after a series of deposit and withdrawal transactions of equal amounts, the final account balance remains 0.


it("Property test", async () => {
    await fc.assert(
      fc.asyncProperty(fcUseModelArgs(), fc.boolean(), async (args, early) => {
        const { model, source, dispose, ready } = early
          ? useModel(...args)
          : await useModel(...args);
        if (early) await ready;

        const model_ = model.value;
        assertDefined(model_);

        const options = args?.[0];

        const expectedLanguage = options?.language ?? "python";
        expect(model_.getLanguageId()).toBe(expectedLanguage);

        if (isRef(options?.source)) {
          expect(source.value).toBe(options?.source.value);
        }

        const expectedValue = unref(options?.source ?? "");
        expect(model_.getValue()).toBe(expectedValue);

        dispose();
      }),
      { verbose: true, numRuns: 10 }, // NOTE: Error with larger numRuns
    );
  })

Summary: The property should hold that the `useModel` function creates a model with a language ID and value matching the given options, or defaults to "python" and an empty string if no options are provided.


it("is infallible", () => {
			fc.assert(fc.property(arb, xs => f(xs) instanceof Map))
		})

Summary: Verification that the function `f`, when applied to inputs generated by `arb`, always returns an instance of `Map`.


it("is infallible", () => {
			fc.assert(
				fc.property(
					fc.webUrl().map(unsafeParseURL),
					fc.webPath().map(fromString),
					(origin, path) => {
						f(origin)(path)
					},
				),
			)
		})

Summary: The function `f` should handle any combination of parsed web URLs and paths without errors.


it("is infallible", () => {
			fc.assert(
				fc.property(fc.oneof(fc.string(), fc.webPath()), x => {
					f(x)
				}),
			)
		})

Summary: Function `f` processes any string or web path without failure.


it("duplicates the input", () => {
			fc.assert(fc.property(fc.anything(), x => expect(f(x)).toEqual([x, x])))
		})

Summary: Function `f` duplicates the input into a tuple containing two identical elements.


it("applies the function and returns both input and output", () => {
			fc.assert(
				fc.property(nonMaxNumber, n => expect(g(n)).toEqual([increment(n), n])),
			)
		})

Summary: The function `g` applies an increment operation on a non-maximum number and returns a tuple containing the incremented number and the original number.


it("applies the function and returns both input and output", () => {
			fc.assert(
				fc.property(nonMaxNumber, n => expect(g(n)).toEqual([n, increment(n)])),
			)
		})

Summary: The function `g` applies an operation to a number and returns a tuple containing the input and the incremented result.


it("is the dual of toFst", () => {
			fc.assert(
				fc.property(nonMaxNumber, n =>
					expect(g(n)).toEqual(pipe(n, toFst(increment), swap)),
				),
			)
		})

Summary: `g(n)` should equal the result of applying `increment` to `n` with `toFst`, and then `swap`.


it("is equivalent to a functorial toFst", () => {
			fc.assert(
				fc.property(nonMaxNumber, n =>
					expect(pipe(n, f(flow(increment, O.some)))).toEqual(
						pipe(n, toFst(increment), O.some),
					),
				),
			)
		})

Summary: The transformation `flow(increment, O.some)` applied to a number should be equivalent to using `toFst(increment)` followed by `O.some`.


it("is equivalent to a functorial toSnd", () => {
			fc.assert(
				fc.property(nonMaxNumber, n =>
					expect(pipe(n, f(flow(increment, O.some)))).toEqual(
						pipe(n, toSnd(increment), O.some),
					),
				),
			)
		})

Summary: Checking if applying a transformation with `f` and `flow` results in the same output as using `toSnd` followed by `O.some`.


it("is equivalent to identity at runtime", () => {
			fc.assert(
				fc.property(fc.anything(), fc.anything(), (x, y) =>
					expect(f([x, y])).toEqual([x, y]),
				),
			)
		})

Summary: The function `f` applied to a tuple `[x, y]` returns the tuple unchanged, ensuring it behaves as an identity function at runtime.


it("returns identity on identity input", () => {
			fc.assert(
				fc.property(fc.string(), fc.string(), (l, r) =>
					expect(f(identity)([l, r])).toEqual([l, r]),
				),
			)
		})

Summary: Calling function `f` with `identity` and a tuple returns the tuple unchanged.


it("calls both provided functions and returns their outputs in order", () => {
			fc.assert(
				fc.property(fc.string(), x =>
					expect(fanout(O.of)(constant("foo"))(x)).toEqual([O.of(x), "foo"]),
				),
			)
			expect(f)
		})

Summary: `fanout` applies two functions to an input and returns their outputs in order.