Document: fbsource/py/fbcode/later.unittest.case.TestCase

Summary:
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## Summary:
Added comprehensive docstring to the `later.unittest.case.TestCase` class to document its purpose, functionality, and usage patterns. The TestCase class is an enhanced async test case that extends `IsolatedAsyncioTestCase` to provide automatic tracking of asyncio tasks and monitoring of asyncio errors. The docstring includes:

- Overview of the class's core functionality (task leak detection and asyncio error monitoring)
- Key features: automatic detection of un-awaited tasks, monitoring of asyncio logger errors, custom task factory, and isolated event loops
- Usage guidance for the `ignoreTaskLeaks` and `ignoreAsyncioErrors` decorators
- Example code demonstrating typical usage patterns

This documentation helps developers understand how to properly use this specialized test case for async testing while ensuring tasks are properly managed.

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Reviewed By: fried

Differential Revision: D87928508

fbshipit-source-id: 79ab5085735c9c9f8bb048b6a6f5c37b266c739c

Author: generatedunixname893464919433493

later/unittest/case.py

@@ -92,6 +92,29 @@ def ignoreTaskLeaks(test_item: _F) -> _F:
 
 
 class TestCase(AsyncioTestCase):
+    """
+    Enhanced async test case that automatically tracks asyncio tasks and monitors errors.
+
+    This test case extends unittest.IsolatedAsyncioTestCase to provide:
+    - Automatic detection of un-awaited asyncio tasks, failing tests that leak tasks
+    - Monitoring of asyncio logger errors, treating them as test failures
+    - Custom task factory for tracking task lifecycle and management
+    - Isolated event loop per test method for reproducible async testing
+
+    Use @ignoreTaskLeaks decorator on test methods that intentionally create
+    background tasks, or @ignoreAsyncioErrors for tests expecting asyncio warnings.
+
+    Example:
+        class MyAsyncTest(TestCase):
+            async def test_async_operation(self) -> None:
+                result = await some_async_function()
+                self.assertEqual(result, expected_value)
+
+            @ignoreTaskLeaks
+            async def test_background_task(self) -> None:
+                asyncio.create_task(background_operation())
+    """
+
     def _callTestMethod(self, testMethod: Callable[..., None]) -> None:
         ignore_error = getattr(
             self,