test: mock of FileUploader and tiny test validating it

tests/test_input_observation.py

@@ -0,0 +1,67 @@
+from typing import Protocol, runtime_checkable
+import pytest
+from unittest.mock import MagicMock, patch
+
+from io import BytesIO
+#from PIL import Image
+import datetime
+import numpy as np
+    
+#from streamlit.runtime.uploaded_file_manager import UploadedFile # for type hinting
+#from typing import List, Union
+
+from input.input_observation import InputObservation
+
+@runtime_checkable
+class UploadedFile(Protocol):
+    name: str
+    size: int
+    type: str
+    _file_urls: list
+
+    def getvalue(self) -> bytes: ...
+    def read(self) -> bytes: ... 
+
+
+class MockUploadedFile(BytesIO):
+    def __init__(self, 
+                 initial_bytes: bytes,
+                 *, # enforce keyword-only arguments after now
+                 name:str,
+                 size:int,
+                 type:str): 
+        #super().__init__(*args, **kwargs)
+        super().__init__(initial_bytes)
+        self.name = name 
+        self.size = size
+        self.type = type
+        
+        self._file_urls = [None,]
+
+@pytest.fixture
+def mock_uploadedFile():
+    class MockGUIClass(MagicMock):
+        def __init__(self, *args, **kwargs):
+            super().__init__(*args, **kwargs)
+            name = kwargs.get('name', 'image2.jpg')
+            size = kwargs.get('size', 123456)
+            type = kwargs.get('type', 'image/jpeg')
+            self.bytes_io = MockUploadedFile(
+                b"test data", name=name, size=size, type=type)
+            self.get_data = MagicMock(return_value=self.bytes_io)
+    return MockGUIClass
+
+
+# let's first generate a test for the mock_uploaded_file  and MockUploadedFile class
+# - test with valid input
+def test_mock_uploaded_file(mock_uploadedFile):
+    # setup values for the test (all valid)
+    image_name = "test_image.jpg"
+    mock_file = mock_uploadedFile(name=image_name).get_data()
+    
+    #print(dir(mock_file))
+    assert isinstance(mock_file, BytesIO)
+
+    assert mock_file.name == image_name
+    assert mock_file.size == 123456
+    assert mock_file.type == "image/jpeg"