How do you generate dynamic (parameterized) unit tests in python?

Question

I have some kind of test data and want to create a unit test for each item. My first idea was to do it like this:

import unittest

l = [[\"foo\", \"a\", \"a\         


        

Answer 1

Meta-programming is fun, but can get on the way. Most solutions here make it difficult to:

• selectively launch a test
• point back to the code given test's name

So, my first suggestion is to follow the simple/explicit path (works with any test runner):

import unittest

class TestSequence(unittest.TestCase):

    def _test_complex_property(self, a, b):
        self.assertEqual(a,b)

    def test_foo(self):
        self._test_complex_property("a", "a")
    def test_bar(self):
        self._test_complex_property("a", "b")
    def test_lee(self):
        self._test_complex_property("b", "b")

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

Since we shouldn't repeat ourselves, my second suggestion builds on @Javier's answer: embrace property based testing. Hypothesis library:

• is "more relentlessly devious about test case generation than us mere humans"
• will provide simple count-examples
• works with any test runner

• has many more interesting features (statistics, additional test output, ...)

  class TestSequence(unittest.TestCase):

  @given(st.text(), st.text())
  def test_complex_property(self, a, b):
      self.assertEqual(a,b)
  

To test your specific examples, just add:

    @example("a", "a")
    @example("a", "b")
    @example("b", "b")

To run only one particular example, you can comment out the other examples (provided example will be run first). You may want to use @given(st.nothing()). Another option is to replace the whole block by:

    @given(st.just("a"), st.just("b"))

Ok, you don't have distinct test names. But maybe you just need:

• a descriptive name of the property under test.
• which input leads to failure (falsifying example).

Funnier example