Add tests using mocker to main.py

[sweep-nightly]

Description

This PR adds tests to the main.py file using a mocker. The tests cover the data loading and preprocessing steps, as well as the model definition. The tests ensure that the code in main.py is working as expected.

Summary of Changes

• Created a new file named test_main.py in the src directory.
• Imported the necessary modules for testing, including pytest and the mocker fixture from pytest-mock.
• Imported the necessary functions and classes from main.py that needed to be tested.
• Wrote a test function for the data loading and preprocessing steps. Used the mocker to mock the DataLoader and the MNIST dataset. Checked if the DataLoader was called with the correct arguments.
• Wrote a test function for the model definition. Used the mocker to mock the model. Checked if the model was instantiated correctly.

Please review and merge this PR. Thank you!

Fixes #10.

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Rollback Files For Sweep

• Rollback changes to src/test_main.py

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