When debugging failing tests, pytest has built-in support for dropping into Python’s debugger (pdb) automatically when a test fails or at specific breakpoints.

Run pytest with the --pdb flag:

pytest --pdb

This will pause execution and open an interactive pdb session whenever a test fails, allowing you to inspect variables, step through code, and understand what went wrong.

For manual breakpoints, add this to your test code:

def test_something():
    result = complex_calculation()
    breakpoint()  # Drops into pdb here
    assert result == expected

Useful pdb commands:

• l (list) - Show surrounding code
• p variable_name - Print a variable’s value
• n (next) - Execute the next line
• c (continue) - Continue execution
• q (quit) - Exit the debugger

This is especially helpful when trying to understand why a test is failing or to explore the state of your application during test execution.

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