API Testing
Envoy Proxy powers many service meshes (Istio, AWS App Mesh) and API gateways (Contour, Emissary-Ingress). It's highly capable and highly complex. Testing Envoy configurations before deploying them prevents outages caused by misconfigured filter chains, broken xDS configs, and subtle routing mistakes. This guide covers testing Envoy's
API Testing
AWS Cognito provides user authentication, authorization, and identity management for AWS-hosted applications. Testing Cognito integrations is critical — a misconfigured user pool can lock users out, a broken Lambda trigger can block all signups, and a wrong JWT audience claim can silently reject valid users. This guide covers testing Cognito user
API Testing
An API gateway is one of the most critical components in a modern backend architecture. It handles authentication, rate limiting, routing, request transformation, and more — all before a request reaches your application code. When the gateway misbehaves, everything downstream breaks. Testing it thoroughly is non-negotiable. This guide covers the full
Testing
SPF, DKIM, and DMARC misconfigurations are the most common reason transactional emails land in spam. This guide shows how to validate these DNS records in CI so you catch deliverability regressions before they reach production users. We cover automated DNS checks, DKIM signature verification, and integration with GitHub Actions. Why
AI Testing
Prompts are code. Changing a single word in a system prompt can break a feature that was working fine. Without version control and regression testing for prompts, you're flying blind — every prompt change is a gamble. This guide covers how to version control prompts, run regression evals on
Testing
Mixpanel powers product analytics for funnels, retention, and segmentation. Testing Mixpanel integrations requires mocking the SDK, validating event schemas against your Lexicon, testing people property updates, and isolating test environments so CI events don't corrupt your production data. This guide covers all of this with practical Jest examples
DevOps
Crossplane Compositions map abstract claims (XR) to concrete managed resources. A bug in patch-and-transform logic can create the wrong resources or delete existing ones when a new claim is submitted. crossplane beta render validates Composition logic locally without touching a real Kubernetes cluster. uptest runs integration tests that create and
Testing
MailHog is the classic local SMTP catcher—simple, lightweight, widely used, and no longer maintained. Mailpit is its modern replacement: faster, ARM-native, with a cleaner API and better CI support. Mailtrap is the cloud-hosted option with spam analysis and team collaboration. This comparison covers all three so you can pick
Testing
Mailtrap's Email Testing API lets you write real assertions against captured emails in Node.js—subject line, HTML body, attachments, spam score—without sending anything to real inboxes. This guide shows how to integrate Mailtrap into Jest tests and CI pipelines so every code path that sends email
DevOps
AWS CDK generates CloudFormation templates from TypeScript, Python, or Java code. The CDK Assertions library lets you test the generated template — verifying resource configurations without deploying anything. CDK snapshot tests catch unintended template changes. CDK integ tests validate actual deployments in real AWS accounts. Together, these three patterns give you
Testing
PostHog combines product analytics, feature flags, session recording, and A/B testing in one platform. Testing PostHog integrations requires more than mocking — you need to test feature flag evaluation, verify event tracking, and ensure session recording is properly configured without capturing sensitive data. This guide covers all three layers with
AI Testing
Eval-driven development (EDD) applies the discipline of TDD to LLM application development. Instead of writing unit tests for deterministic code, you write evals that define what "good" looks like for your AI — before building the feature. Failing evals are your spec. This guide covers how to structure evals