Add Unit Test

Add unit test

Steps

1. Find an existing test for a similar function. Match its style — class-based vs functional, parametrize vs loop, mocking style.
2. Locate the test file. Conventions vary: tests/test_foo.py, test_foo.py next to foo.py, or src/foo/_test.py. Don't invent a new one.
3. Test the public behavior, not implementation details. Edge cases first: empty input, boundary values, error paths.
4. Avoid mocking yfinance / requests / DB clients by isolating logic from I/O — pass dataframes/dicts to pure functions and let the network boundary live in one place.
5. Run only the new test first (pytest -k test_<name> or python -m unittest test_module.TestClass.test_method) to confirm it actually exercises the change.
6. Then run the full suite with {{ profile.test_command if profile and profile.test_command else "the project test_command" }}.

Failure modes to avoid

• Adding pytest fixtures when the project uses plain unittest.
• Testing the test framework instead of the function ("assert test runner works").
• Mocking the world — if you're mocking 5 things to test one function, refactor.
• Writing tests that pass only with the implementation in front of you (write the test first if you can).