Understanding testing and unit tests

Whenever I was managing or mentoring another developer and they wanted to make a change to a system I’d ask them a question: “How can you be sure your change won’t break things?”

This simple question can be deceptively hard to answer, but every answer I’ve ever heard boils down to a single concept: testing.

I define testing as the process of verifying software functionality and detecting unwanted changes to program behavior.

This testing could be done by a human, such as a developer or a quality assurance analyst, or it could be done via software, depending on the type of test involved.

Types of tests and the testing pyramid

Testing is a broad field that encompasses many different types of activities, including the following:

• Manual testing, which involves a person performing some activity manually and verifying the outcome.
• Exploratory testing, a subset of manual testing that focuses...