Page 4 - PHPUnit

Anyone who writes tests without a clear pattern ends up with a test suite that is slow, brittle and hard to understand. Data providers, meaningful assertions, isolated mocks and a sensible coverage strategy separate tests that immediately catch a refactoring mistake from green tests that stay green despite bugs.

A single project wide coverage number sounds reassuring, but it can hide exactly the core modules that need tests most urgently. Defining coverage thresholds per module and enforcing them in the CI pipeline protects the highest risk areas specifically, instead of being deceived by a favorable average.

Code coverage sounds like a simple concept, but it quickly becomes a bottleneck in large Magento 2 projects: Xdebug slows the test suite down by a factor of five to ten, reports become huge, and without proper configuration you end up measuring the wrong thing. PCOV, targeted whitelist configuration and CI thresholds turn coverage into a useful tool instead of a bottleneck.

Remote development in PhpStorm is more than SFTP upload and hoping for the best. With the right SSH setup, a configured remote interpreter, port forwarding for Xdebug, and the JetBrains Remote Development mode, you can work on distant servers with the same IDE experience as locally.

Filesystem operations are among the most frequently untested parts of PHP applications. Anyone who calls file_get_contents() and file_put_contents() directly ends up writing code that either doesn't get tested at all, or leaves behind tests that create real files, have order dependencies, and break when run in parallel. vfsStream, stream wrappers and filesystem abstraction solve this problem at its root.

A legacy project with zero test coverage feels like a wall with no handhold. With characterization tests as a starting point, clear risk based prioritization, and realistic milestones, you can build a resilient PHPUnit baseline step by step, without overwhelming the team with an unrealistic all or nothing goal.

A hundred percent code coverage says nothing about whether tests would actually catch bugs. Mutation testing with Infection artificially injects small faults into Symfony code and checks whether the test suite reliably catches every single one of them.

Anyone who does not deliberately test exceptions leaves error handling unverified, which is the most dangerous blind spot in a PHP test suite. PHPUnit provides precise methods to ensure that the correct exception type, the right message, and the correct error code are actually raised.

Anyone who wants to refactor legacy code without tests faces a chicken-and-egg problem: writing tests requires understanding the code, understanding requires reading the code, but confidence when changing it requires tests. Golden Master tests untangle this knot, they test the behavior before it is understood.

Two independently deployable PHP services communicating over an API can each have a fully green test suite and still become incompatible. Contract tests with PHPUnit close exactly this gap between provider and consumer.