Tidy up usage of assertEqual in tests

[Alasdair Nicol]

There are a few places in the tests where we are using self.assertEqual that could be more idiomatic.

self.assertEqual(None, x)  # prefer self.assertIsNone(x)
self.assertEqual(True, x in y) # prefer self.assertIn(x, y)


self.assertEqual(True, x)  # self.assertTrue(x) may be appropriate, but care is needed because it will pass for truthy values
self.assertEqual(False, x)  # self.assertFalse(x) may be appropriate, but care is needed because it will pass for falsey values
self.assertEqual(True, x == y) # prefer self.assertEqual(x, y)

I found these using the following greps

grep -rI assertEqual.True
grep -rI assertEqual.False
grep -rI assertEqual.None

This is a similar tidy up to #23620

[Alasdair Nicol]

Pull request ​https://github.com/django/django/pull/4570

[Alasdair Nicol]

As mentioned by Tim on the pull request, it is not always appropriate to use self.assertTrue and self.assertFalse, as these will pass for truthy and falsey values. I have updated the ticket description and pull request.