Testing
When to Use Mocks vs Stubs in Unit Testing
"Just mock it" is the most common piece of testing advice—and one of the most misused.
Unit Testing
Unit testing guides — write fast, reliable unit tests with Jest, Vitest, pytest, and other frameworks.
Latest
Jest
Advanced Jest Mocking: Timers, ESM & Complex Dependencies
You've covered jest.fn() and jest.mock(). Now you're staring at a test that needs to control setTimeout, mock an ES module, or stub a class constructor.
Shift-Left Testing
Building a Unit Testing Culture for Shift-Left Success
Shift-left testing has a culture problem. Teams adopt the tooling — CI pipelines, coverage reporters, test frameworks — but neglect the human side.
Godot
GUT Advanced: Mocking, Signals, and Async Testing in Godot 4
GUT (Godot Unit Test) is the de-facto testing framework for Godot projects, and Godot 4 brought significant changes to GDScript that affect how you write and structure tests. If you've gone through the GUT getting-started tutorials and written basic assert_eq tests, this guide covers the
Testing
Robolectric: Unit Testing Android Apps Without an Emulator
Robolectric runs Android tests on the JVM — no emulator, no device, no waiting for adb to connect.
Visual Testing
Loki: Storybook Visual Regression Testing
Loki is a visual regression testing tool purpose-built for Storybook. It runs locally and in CI, captures screenshots of every story, compares them against stored references, and shows diffs when components change. Unlike cloud-hosted alternatives, Loki stores reference images in your repository and runs entirely offline. Why Loki
Visual Testing
Happo: Cross-Browser Visual Testing for UI Components
Happo solves a specific problem: visual regression testing across multiple browsers simultaneously.
Visual Testing
Lost Pixel: Open-Source Visual Regression Testing
Visual regression testing catches UI changes that unit tests miss. Lost Pixel is an open-source visual regression testing platform that compares screenshots of components or pages across commits, flags differences, and integrates with your existing CI pipeline. Unlike hosted-only tools, Lost Pixel can run entirely in your own
Clojure
re-frame-test: Testing re-frame Applications
re-frame's unidirectional data flow — events → effects → db → subscriptions → views — makes applications predictable. It also makes them testable.
Clojure
Generative Testing with test.check in Clojure
Example-based tests check specific cases. Property-based tests check invariants across hundreds of randomly generated inputs.
Clojure
Kaocha Test Runner: Advanced Configuration and Plugins
Kaocha is the most flexible test runner in the Clojure ecosystem. While lein test and clojure -M:test get you started, Kaocha gives you fine-grained control over test selection, execution order, output formatting, and extensibility through plugins. This guide covers advanced Kaocha configuration for teams that need more than
Clojure
Babashka Scripting with Tests: bb.edn and babashka.test
Babashka is a native Clojure scripting runtime that starts in milliseconds.