java_jars.md

## What are those paths?

Those are hardcoded locations where the code expects to find the **JUnit Platform Console Standalone JAR** — a self-contained JAR that can both compile and run JUnit 5 tests without needing a build tool like Maven or Gradle.

The code checks three candidate paths in order and uses the first one it finds. These paths are Docker container paths (not your local machine), so they need to be present inside whatever container runs your environment.

## How to get the JAR in place

**1. Download it locally first**

Go to Maven Central and grab it:
```
https://repo1.maven.org/maven2/org/junit/platform/junit-platform-console-standalone/
```
Pick the latest version (e.g. `1.10.2`), download `junit-platform-console-standalone-1.10.2.jar`.

Or via `curl`:
```bash
curl -L -o junit-platform-console-standalone.jar \
  https://repo1.maven.org/maven2/org/junit/platform/junit-platform-console-standalone/1.10.2/junit-platform-console-standalone-1.10.2.jar
```

**2. Put it in your Dockerfile**

Since the first candidate path is `/app/junit-platform-console-standalone.jar`, the cleanest approach is to add this to your `Dockerfile`:

```dockerfile
FROM openjdk:17-slim   # or whatever base you're using

# Install JUnit standalone jar
RUN curl -L -o /app/junit-platform-console-standalone.jar \
  https://repo1.maven.org/maven2/org/junit/platform/junit-platform-console-standalone/1.10.2/junit-platform-console-standalone-1.10.2.jar

# ... rest of your Dockerfile
```

Or if you've already downloaded it and want to COPY it in:
```dockerfile
COPY junit-platform-console-standalone.jar /app/junit-platform-console-standalone.jar
```

**3. Verify it works inside the container**

```bash
java -jar /app/junit-platform-console-standalone.jar --version
```

## Why a standalone JAR?

The code avoids Maven/Gradle entirely — it manually calls `javac` to compile and then `java -jar junit...jar --select-class TestClass` to run. The standalone JAR bundles everything JUnit 5 needs (the launcher, engine, assertions API) in a single file, making it suitable for this kind of scripted sandbox where you don't want a full build system.