Assertions are the mechanism we use to tell unittest what the important outcomes of the test are. By using appropriate assertions, we can tell unittest exactly what to expect from each test.

The assertTrue method

When we call self.assertTrue(expression), we're telling unittest that the expression must be true in order for the test to be a success.

This is a very flexible assertion, since you can check for nearly anything by writing the appropriate Boolean expression. It's also one of the last assertions you should consider using, because it doesn't tell unittest anything about the kind of comparison you're making, which means that unittest can't tell you clearly what's gone wrong if the test fails.

For example, consider the following test ...

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