What tools and methodologies do you use for testing your code or systems?

For testing code and systems, I use several approaches and tools:

• Unit testing with frameworks such as JUnit for Java or pytest for Python. This allows checking individual functions and classes for correctness.
• Integration testing to ensure that different system components work together as expected.
• Test automation using CI/CD systems (Jenkins, GitLab CI) so that tests run automatically with each code change.
• Code review — peer review helps identify errors and improve quality.
• Static code analysis with tools (SonarQube, ESLint) to find potential issues.
• Manual testing in cases where automation is difficult or UX verification is needed.

Example of a simple unit test in Python with pytest:

# function to test
 def add(a, b):
     return a + b

# test
 def test_add():
     assert add(2, 3) == 5
     assert add(-1, 1) == 0

This approach helps ensure that changes do not break existing functionality.