Testing
Rust has three places to write tests: inline in the source file, in a tests/ directory for integration tests, and in doctests. Most guides cover these in isolation. This guide covers how to organize them as your project grows — shared utilities, feature-gated tests, test fixtures, and keeping test code
Rust
Code coverage tells you which lines your tests exercise. It won't tell you if your tests are good, but it does tell you what you're definitely not testing. In Rust, you have two main options: cargo-tarpaulin and cargo-llvm-cov. This guide covers both, when
Testing
Engineering teams spend significant time debating whether their testing practices are working. The conversation usually goes in circles because it's based on impressions, not data. "Tests feel slow." "CI seems flakier lately." "Coverage has been dropping." Measuring your testing pipeline turns these
Testing
Detox and Appium are the two dominant mobile E2E testing frameworks, but they take fundamentally different approaches. Detox is a gray-box framework purpose-built for React Native — fast and reliable but React Native only. Appium is a black-box framework that works with any mobile app on any platform
Testing
Rust's error handling is excellent but undertested. Most Rust codebases test the happy path thoroughly and treat error paths as "it compiles, must be right." But error handling bugs — wrong error type returned, missing context in error messages, error chains that lose important information — cause real
Rust
```tldr Rust's embedded ecosystem has first-class testing support: defmt-test runs tests directly on-target with RTT output, QEMU lets you run ARM Cortex-M tests on a developer machine, and embedded-hal-mock lets you unit test peripheral drivers without hardware at all. Most embedded Rust
Testing
Detox is a gray-box end-to-end testing framework for React Native that synchronizes test execution with your app's internal state — eliminating the sleep() calls and timing hacks that make black-box tests brittle. This guide covers the architecture that makes Detox work and walks you through
React Native
A hands-on guide to Detox E2E testing in React Native, covering project setup, device and element APIs, synchronization with async operations, and running Detox in CI environments like GitHub Actions. Detox is the industry-standard end-to-end testing framework for React Native. Unlike Jest + RNTL which runs in
Testing
Rust CLI applications have a unique testing challenge: you can unit test the business logic, but testing the actual binary — argument parsing, output formatting, exit codes — requires running the compiled program. assert_cmd is the standard crate for this. This guide covers end-to-end CLI testing with assert_cmd
Testing
Running Detox tests in CI requires matching simulator/emulator availability to your runner OS, caching dependencies, and handling the slow parts (app builds, simulator boot) efficiently. This guide covers complete CI configurations for GitHub Actions and GitLab CI for both iOS and Android. Key Takeaways * iOS requires macOS runners — this
Test Strategy
Unit tests catch logic errors. Integration tests catch interface mismatches. But a category of bugs only appears when software runs in the real world — under load, with real data, in unpredictable sequences. Runtime testing is the discipline for finding those. This guide covers the strategies, tools, and thinking behind effective
Testing
Flaky Detox tests almost always come from one of three sources: broken synchronization (the app isn't idle when Detox thinks it is), poor test isolation (state from one test bleeds into the next), or incorrect element selectors (the testID you're targeting doesn't exist in