jimmc414 verify-with-inline-tests
When to Use
- Tests should be near the code
- Tests serve as documentation
- Single-file modules
- Quick verification during development
When NOT to Use
- Large test suites
- Need test isolation
- CI/CD expects tests in specific location
The Pattern
Include tests in the module, run them when module is executed directly.
def my_function(x):
"""Do something useful."""
return x * 2
def test():
"""Run all tests."""
assert my_function(2) == 4
assert my_function(0) == 0
assert my_function(-1) == -2
print("All tests pass.")
if __name__ == '__main__':
test()
Example (from pytudes)
# sudoku.py - structural invariant tests
def test():
"""A set of tests that must pass."""
assert len(squares) == 81
assert len(unitlist) == 27
assert all(len(units[s]) == 3 for s in squares)
assert all(len(peers[s]) == 20 for s in squares)
assert units['C2'] == [
['A2', 'B2', 'C2', 'D2', 'E2', 'F2', 'G2', 'H2', 'I2'],
['C1', 'C2', 'C3', 'C4', 'C5', 'C6', 'C7', 'C8', 'C9'],
['A1', 'A2', 'A3', 'B1', 'B2', 'B3', 'C1', 'C2', 'C3']
]
print('All tests pass.')
if __name__ == '__main__':
test()
solve_all(open("sudoku-easy50.txt"), "easy")
solve_all(open("sudoku-top95.txt"), "hard")
# spell.py - comprehensive unit tests
def unit_tests():
assert correction('speling') == 'spelling'
assert correction('korrectud') == 'corrected'
assert correction('bycycle') == 'bicycle'
assert words('This is a TEST.') == ['this', 'is', 'a', 'test']
assert len(WORDS) == 32198
assert sum(WORDS.values()) == 1115585
assert 0.07 < P('the') < 0.08
return 'unit_tests pass'
if __name__ == '__main__':
print(unit_tests())
spelltest(Testset(open('spell-testset1.txt')))
Key Principles
if __name__ == '__main__': Only run tests when executed directly- Assert for tests: Simple, clear assertions
- Print success: Confirm tests ran
- Test structure first: Validate data structures built correctly
- Tests as examples: Show how functions are used