PHPUnit

Read following articles to start writing unit tests for WordPress.

• Setup and Run PHPUnit
• Writing PHPUnit Tests

Must Read

Tutorial by Pippin

• Unit Tests for WordPress Plugins
• Unit Tests for WordPress Plugins – Tests vs. Assertions

Using WP-CLI

Following commands to generate files needed for running PHPUnit tests in a plugin/theme.

• wp scaffold plugin-tests
• wp scaffold theme-tests

References

• Getting Started with PHPUnit