expecttest

expecttest

We use expecttest for testing. If you need to match against a multiline string or some output that is likely to change in the future (e.g., the kind of thing you would have ordinarily done an assertIn with), use an expect test. If a test is assertExpectedInline and it fails, use 'accept' command to update the output, do NOT relax the test. If the output of the test seems nondeterministic (e.g., you run accept but the test is still failing on the assertExpectedInline) you should halt and ask for help from the user.

Below is its README.

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This library implements expect tests (also known as "golden" tests). Expect tests are a method of writing tests where instead of hard-coding the expected output of a test, you run the test to get the output, and the test framework automatically populates the expected output. If the output of the test changes, you can rerun the test 'accept' command to accept the output.

Somewhat unusually, this library implements inline expect tests: that is to say, the expected output isn't saved to an external file, it is saved directly in the Python file (and we modify your Python file when updating the expect test.)

The general recipe for how to use this is as follows:

1. Write your test and use assertExpectedInline() instead of a normal assertEqual. Leave the expected argument blank with an empty string:

   self.assertExpectedInline(some_func(), """""")
   

2. Run your test. It should fail, and you get an error message about accepting the output with EXPECTTEST_ACCEPT=1 (this means to use 'accept' command)

3. Rerun the test with 'accept' command. Now the previously blank string literal will contain the expected value of the test.

   self.assertExpectedInline(some_func(), """my_value""")
   

A minimal working example:

# test.py
import unittest
from expecttest import TestCase

class TestStringMethods(TestCase):
    def test_split(self):
        s = 'hello world'
        self.assertExpectedInline(str(s.split()), """""")

if __name__ == '__main__':
    unittest.main()

Run accept command, and the content in triple-quoted string will be automatically updated, so you don't have to fill it out yourself.