Unit Testing in Python

This project contains two main packages: mypackage for development code and test for testing code.

Coding Conventions for unittest

To enable automatic test discovery in your project directory, it is essential to follow specific coding and naming conventions for your test code. The examples in this book consistently adhere to these conventions.

Key Conventions

• Test File Structure: All test files must be either modules or packages that can be imported from the project's top-level directory.
• Starting Point: Test discovery begins from the current directory by default.
• Filename Pattern: By default, test discovery looks for files matching the pattern test*.py.

Common Assertions

Here’s a summary of the most commonly used assertions in the unittest framework along with their purposes:

Method	Checks That
assertEqual(a, b)	a == b
assertNotEqual(a, b)	a != b
assertTrue(x)	bool(x) is True
assertFalse(x)	bool(x) is False
assertIs(a, b)	a is b
assertIsNot(a, b)	a is not b
assertIsNone(x)	x is None
assertIsNotNone(x)	x is not None
assertIn(a, b)	a in b
assertNotIn(a, b)	a not in b
assertIsInstance(a, b)	isinstance(a, b)
assertNotIsInstance(a, b)	not isinstance(a, b)
assertAlmostEqual(a, b)	round(a-b, 7) == 0
assertNotAlmostEqual(a, b)	round(a-b, 7) != 0
assertGreater(a, b)	a > b
assertGreaterEqual(a, b)	a >= b
assertLess(a, b)	a < b
assertLessEqual(a, b)	a <= b
assertRegexpMatches(s, r)	r.search(s)
assertNotRegexpMatches(s, r)	not r.search(s)
assertItemsEqual(a, b)	sorted(a) == sorted(b)
assertDictContainsSubset(a, b)	All key/value pairs in a exist in b

Comparison Methods

These methods are used to compare various types of data structures:

Method	Used to Compare
assertMultiLineEqual(a, b)	Strings
assertSequenceEqual(a, b)	Sequences
assertListEqual(a, b)	Lists
assertTupleEqual(a, b)	Tuples
assertSetEqual(a, b)	Sets or frozensets
assertDictEqual(a, b)	Dictionaries

Skipping tests

unittest provides a mechanism for skipping tests, conditionally or unconditionally.

It uses the following decorators for implementing the skipping mechanism:

• unittest.skip(reason): Unconditionally skips the decorated test. reason should describe why the test is being skipped.
• unittest.skipIf(condition, reason): Skips the decorated test if condition is true.
• unittest.skipUnless(condition, reason): Skips the decorated test unless condition is true.
• unittest.expectedFailure(): Marks the test as an expected failure. If the test fails when it runs, the test is not counted as a failure.

assertRaises()

The assertRaises() method is used to check if the code block raises the exception mentioned in assertRaises(). If the code raises the exception then the test passes; otherwise, it fails.