PHPUnit tests for HTML output are fragile. Attribute order changes, a trailing semicolon, and suddenly tests fail — even though the browser renders the same thing. WordPress 6.9 adds assertEqualHTML() to WP_UnitTestCase. It compares HTML semantically, so only real differences cause failures.
This tutorial shows WordPress plugin developers how to add automated unit testing from setup to GitHub integration. Learn to catch bugs before users do, prevent regressions in stable code, and build confidence across different WordPress versions and configurations.