Testing

Testing ViewModels

How to unit test MVVM ViewModels in isolation, covering state assertions, command execution, async flows, and dependency mocking.

Unit Testing in .NET

How to write fast, isolated unit tests for .NET applications using xUnit and Moq, and the practices that keep a test suite trustworthy.

Unit Testing MVC Controllers

Learn practical techniques for isolating and testing ASP.NET MVC controller actions using xUnit or NUnit with Moq, including ActionResult assertions and model…

Testing and Debugging Teams Apps

Practical techniques for local debugging, testing SSO and bots, and diagnosing issues in production Teams apps.

Unit Testing with the In-Memory Provider

How to use EF Core's InMemory provider and SQLite in-memory mode to test data access code, and where each approach falls short.

Testing Blazor Components with bUnit

Learn how to write fast, reliable unit tests for Blazor components using bUnit, from rendering and interaction to mocking dependencies.

Integration Testing with WebApplicationFactory

Use Microsoft.AspNetCore.Mvc.Testing's WebApplicationFactory to spin up an in-memory ASP.NET Core app and test real HTTP requests through the full middleware p…

Unit Testing Controllers and Services

Learn how to isolate ASP.NET Core controllers and services with xUnit and Moq to verify business logic without running the full HTTP pipeline.

Testing Async Code: Promises and async/await

Learn the correct patterns for testing promise-based and async/await code in Jest, and the pitfalls that let async bugs slip past a green test run.

beforeAll() and afterAll()

Understand how Jest's beforeAll() and afterAll() hooks handle one-time, expensive setup and teardown shared across an entire test suite.

beforeEach() and afterEach()

Learn how Jest's beforeEach() and afterEach() hooks establish and tear down consistent test state so every test runs in isolation.

Code Coverage with Jest

Understand how Jest measures code coverage across statements, branches, functions, and lines, and how to enforce thresholds in CI.

Common Matchers: toBe, toEqual, toContain

Learn how Jest's core matchers toBe, toEqual, and toContain compare values, objects, and collections, and when to reach for each one.

Writing Custom Matchers

Learn how to extend Jest's expect with expect.extend() to write custom matchers that produce clearer, more expressive assertions and failure messages.

Installing and Configuring Jest

How to add Jest to a JavaScript or TypeScript project, and the key configuration options in jest.config.js.

Jest Best Practices

Practical guidelines for writing fast, reliable, and maintainable Jest test suites that catch real bugs without becoming brittle.

Jest Configuration: Multi-Project Setups

Learn how to configure Jest's projects array to run multiple test environments and configurations, like unit and integration suites, from a single Jest invocat…

Jest in CI/CD Pipelines

How to configure Jest to run reliably, quickly, and with useful reporting inside continuous integration pipelines.

Jest in Monorepos

Learn how to configure Jest to run efficiently across multiple packages in a monorepo, covering shared config, workspace-aware discovery, and CI caching.

Jest Interview Questions

Common Jest interview topics covering mocks, async testing, fake timers, and module mocking, with the reasoning behind each answer.

Jest Quick Reference

A condensed cheat sheet of essential Jest CLI flags, matchers, lifecycle hooks, and config keys for day-to-day use.

Jest vs Vitest vs Mocha

How Jest compares to Vitest and Mocha in philosophy, speed, and ecosystem so you can pick the right test runner.

Mock Functions with jest.fn()

Learn how to create, configure, and inspect Jest mock functions to isolate units under test and verify how dependencies are called.

Mocking HTTP Requests

Learn how to mock network calls in Jest tests using axios/fetch stubs, interceptor libraries like nock and msw, and how to simulate error and timeout scenarios.

Testing Python Code with pytest: A Beginner's Guide

Untested code is legacy code from the moment it's written. This guide explains how to write effective Python tests with pytest — from your first test function…

Python Pytest Cheat Sheet

Covers writing pytest test functions, fixtures with setup/teardown, parametrized tests, and the most useful command-line options.

TypeScript Type Guards Cheat Sheet

Covers narrowing with typeof, instanceof, the in operator, custom type predicates, and assertion functions for safer runtime checks.

Java JUnit Testing Cheat Sheet

Covers JUnit 5 test lifecycle annotations, assertions, parameterized tests, and Mockito mocking patterns for writing effective unit tests.

Go Interfaces Cheat Sheet

Explains Go's implicit interface satisfaction, type assertions and type switches, the empty interface, and idiomatic small-interface design.

Go Testing Cheat Sheet

Covers writing unit tests and table-driven tests with the testing package, subtests, benchmarks, and running tests with the go test CLI.

Rust Cargo Cheat Sheet

Reference for Cargo commands, Cargo.toml structure, dependency management, workspaces, and common cargo subcommands for building and testing Rust projects.

Kotlin Null Safety Cheat Sheet

Covers nullable types, the safe call and elvis operators, the not-null assertion, and platform types for handling null safely in Kotlin.

Unit Testing Best Practices Cheat Sheet

The Arrange-Act-Assert pattern, mocking external dependencies, parametrized tests, and the FIRST principles for writing reliable unit tests.

Scikit-learn Cheat Sheet

Core scikit-learn workflow covering train/test splitting, pipelines, preprocessing, common estimators, cross-validation, hyperparameter tuning, and evaluation…

A/B Testing Cheat Sheet

A practical guide to designing, running, and statistically analyzing A/B tests, covering sample size, significance testing, and common pitfalls.

Hypothesis Testing Cheat Sheet

Core statistical hypothesis testing concepts and workflows, covering t-tests, chi-square tests, p-values, and confidence intervals with scipy.

Load Testing (JMeter/k6) Cheat Sheet

Designing and running load tests with JMeter and k6 to validate performance, throughput, and breaking points.

Penetration Testing Basics Cheat Sheet

Introduces the penetration testing methodology, phases, common toolsets, and reporting practices used in authorized security assessments.

Burp Suite Cheat Sheet

Covers Burp Suite's core web application testing workflow including proxy setup, Repeater, Intruder, and scanning best practices.

SSL/TLS Deep Dive Cheat Sheet

Explains the TLS handshake, protocol versions, cipher suites, and practical OpenSSL commands for testing and hardening TLS configurations.

Postman API Testing Cheat Sheet

A reference for building requests, using variables, writing test scripts, and running collections in Postman.

Test-Driven Development (TDD) Cheat Sheet

Covers the red-green-refactor loop, writing the smallest failing test first, test doubles, and common TDD anti-patterns to avoid.

Synthetic Data Generation Cheat Sheet

Practical techniques and libraries for generating synthetic tabular, text, and image data for ML training and privacy-safe testing.

Bun Runtime Cheat Sheet

Bun's built-in APIs for HTTP servers, file I/O, bundling, testing, and package management as a fast Node.js-compatible runtime.

Accessibility Testing Tools Cheat Sheet

CLI and code snippets for axe-core, Lighthouse, Pa11y, and jest-axe to automate WCAG accessibility checks in development and CI.

Storybook Cheat Sheet

Component story format (CSF3), args, decorators, addons, and interaction testing syntax for building an isolated UI component workshop.

Continuous Integration vs Continuous Deployment

Continuous Integration (CI) is the practice of frequently merging code into a shared branch with each merge automatically built and tested, while Continuous De…