inline-snapshot. I'm a big fan of snapshot testing, where expected values are captured the first time a test suite runs and then asserted against in future runs. It's a very productive way to build a robust test suite.
inline-snapshot by Frank Hoffmann is a particularly neat implementation of the pattern. It defines a snapshot() function which you can use in your tests:
assert 1548 * 18489 == snapshot()
When you run that test using pytest --inline-snapshot=create the snapshot() function will be replaced in your code (using AST manipulation) with itself wrapping the repr() of the expected result:
assert 1548 * 18489 == snapshot(28620972)
If you modify the code and need to update the tests you can run pytest --inline-snapshot=fix to regenerate the recorded snapshot values.