Database
Untested migrations are one of the highest-risk deployments in software engineering — a bad migration can corrupt production data in seconds with no undo. This post covers a systematic approach to testing forward migrations, rollback paths, data integrity invariants, and zero-downtime patterns like expand/contract, all using TestContainers so your CI
Drizzle
Drizzle ORM's SQL-first design makes it highly testable: you can run queries against in-memory SQLite for fast unit tests, swap in a real Postgres container for integration tests with minimal code changes, and validate your schema definitions statically. This post walks through all three layers and shows how
Apollo Server
Apollo Server v4 introduced a cleaner testing API centered on executeOperation, which lets you run full GraphQL operations without spinning up an HTTP server. This post covers testing resolvers, DataSources, authentication via context, subscriptions with graphql-ws, and how to use snapshot testing effectively for GraphQL responses — all with Jest. Key
DevOps
Pulumi programs are real code — TypeScript, Python, Go — which means you can test them with standard testing frameworks. Pulumi's built-in mocking system lets you unit test your infrastructure definitions without deploying anything to the cloud. For end-to-end validation, Pulumi Automation API runs real deployments in tests. This guide
AI Testing
A golden dataset is a curated set of inputs with known-good outputs (or evaluation criteria) used to measure whether your LLM application is working correctly. Without one, you're evaluating against vibes. This guide covers how to build, annotate, version, and maintain golden datasets for LLM applications — from initial
Testing
Amplitude tracking bugs are silent — the app works, but your growth metrics are wrong. Funnel drop-offs appear where users actually convert. Revenue numbers are off. This guide covers how to unit test Amplitude SDK tracking with Jest mocks, validate event schemas against your taxonomy, test funnel event sequences, and verify
React Native
@testing-library/react-native brings the same user-centric testing philosophy to mobile that Testing Library brought to the web. This guide covers component rendering, custom hook testing with renderHook, mocking stubborn native modules, taming async state with waitFor and findBy, and the act() gotchas that trip up even experienced React Native developers.
Detox
Detox is a gray-box E2E testing framework for React Native that eliminates flakiness by synchronizing with the app's JavaScript thread and native animation system rather than relying on sleep timers. This guide walks through complete iOS and Android setup, the synchronization model that makes Detox reliable, and CI
DevOps
Terraform modules can look correct but deploy broken or insecure infrastructure. Checkov catches security misconfigurations statically before a plan runs. Terratest deploys real infrastructure to validate it works end-to-end. Together, they give you a complete testing pyramid for Terraform: fast static checks in every PR, and real infrastructure validation in
Testing
Broken analytics tracking is one of the hardest bugs to detect — the app works fine, but your data pipeline silently receives malformed events or nothing at all. This guide covers testing Segment analytics.js event tracking: mocking the Segment library, validating event schemas in unit tests, verifying event delivery in
AI Testing
Testing LLM applications is hard because the outputs are open-ended text — there's no single correct answer. LLM-as-judge sidesteps this by using a capable model to score another model's outputs according to defined rubrics. This guide covers the key evaluation patterns: G-Eval for rubric-based scoring, pairwise comparison
Test Automation
RTK Query is Redux Toolkit's built-in data fetching and caching solution. It generates hooks, reducers, and action creators from endpoint definitions — which means testing it requires a different approach than testing hand-written reducers. You need to test the API layer, cache behavior, and the mutations that invalidate it.