pytest_deduplicate

The pytest_deduplicate tool assists in analyzing your test suite to identify potential issues related to duplicate and overlapping tests. By utilizing code coverage information, it pinpoints areas for improvement, leading to a more efficient and focused set of tests.

Benefits

• Reduced Test Suite Size: Eliminating redundant tests results in a more efficient test suite, saving execution time and resources.
• Improved Test Focus: Breaking down large tests into smaller, more specific ones enhances clarity and maintainability.
• Enhanced Code Coverage Analysis: Identifying overlaps and gaps in coverage helps you focus your testing efforts more effectively.

Requirements

• Python 3.x
• pytest or unittest
• coverage

Installation

1. Ensure you have the required libraries installed:

   pip install -r requirements.txt

Usage

1. Run your tests with pytest and include the script as a plugin:

   cd <working_directory>
   /path/to/this/tool/pytest_deduplicate.py [pytest_parameters]

2. Review the output, which will include three sections of information:

   Case	Description	Actionable Insights	Example
   Case 1: Duplicates	Tests with identical code coverage, indicating redundancy.	Remove duplicate tests, keeping the most readable or representative one.	TestSimple.test_even0 and TestSimple.test_even2 have identical coverage.
   Case 2: Broad Coverage ("God Tests")	Tests that cover too much functionality, making them harder to maintain and understand.	Split into smaller, focused tests to improve clarity and maintainability.	TestSimple.test_evenodd can be split into smaller tests like test_even0 and test_odd.
   Case 3: Superseded Tests	Tests whose coverage is entirely contained within another test, making them redundant.	Remove smaller tests if the larger test sufficiently covers the functionality.	TestSimple.test_evenodd supersedes test_even0, test_even2, and test_odd.

Interpreting the Results

• Duplicates: Consider removing duplicate tests, keeping the one that is most readable or representative.
• God Tests: Evaluate splitting these tests into smaller units that focus on specific functionality. This can improve test clarity and maintainability.
• Superseded Tests: Assess whether these tests are truly redundant and can be safely removed. Ensure that removing them doesn't leave any functionality untested.

Note: Be aware of potential false positives, especially in cases involving complex code structures like regular expressions, as the code coverage may appear identical.

Additional Notes

• Consider using code coverage visualization tools alongside this script for a more comprehensive understanding of your test coverage landscape.

Result Example

def function(x):
    if x % 2 == 0:
        for i in range(1, 3):
            print("even")
        return True
    else:
        print("odd")
        return False

def test_even0(self):
    self.assertEqual(function(0), True)

def test_even2(self):
    self.assertEqual(function(2), True)

def test_odd(self):
    self.assertEqual(function(3), False)

def test_evenodd(self):
    self.assertEqual(function(2), True)
    self.assertEqual(function(3), False)

Output:

1. Duplicate tests detected with identical coverage:
tests/test_simple.py:16:1: W001 tests with same coverage: TestSimple.test_even0 consider keeping only one (duplicate-test)
tests/test_simple.py:19:1: W001 tests with same coverage: TestSimple.test_even2 consider keeping only one (duplicate-test)



2. "God test" detected with broad coverage:
tests/test_simple.py:25:1: W002 test TestSimple.test_evenodd can be replaced by smaller tests below (bigger-coverage)
tests/test_simple.py:16:1: I002 test TestSimple.test_even0 covers part of TestSimple.test_evenodd test (smaller-test)
tests/test_simple.py:22:1: I002 test TestSimple.test_odd covers part of TestSimple.test_evenodd test (smaller-test)



3. Superseeded tests:
tests/test_simple.py:25:1: I003 test TestSimple.test_evenodd covers more code than test(s) below (bigger-coverage)
tests/test_simple.py:16:1: W003 test TestSimple.test_even0 covers less code than TestSimple.test_evenodd test. Consider remove it (smaller-coverage)
tests/test_simple.py:19:1: W003 test TestSimple.test_even2 covers less code than TestSimple.test_evenodd test. Consider remove it (smaller-coverage)
tests/test_simple.py:22:1: W003 test TestSimple.test_odd covers less code than TestSimple.test_evenodd test. Consider remove it (smaller-coverage)