test-driven-development

Test-driven development in C# follows the red-green-refactor cycle: write a failing test first using xUnit or similar frameworks, implement minimal code to pass it, then refactor. This ensures every line of production code is backed by a verifiable test and prevents untestable code.

Writing tests first verifies that your tests actually catch failures—you see them fail before writing code. This prevents tests that pass regardless of implementation and ensures bugs are caught early, reducing defects and building confidence in code quality.

Yes. TDD applies to bug fixes, refactoring, and behavior changes across codebases. Write a failing test that reproduces the bug, fix the code minimally, then refactor. This scope covers new features, existing code changes, and quality improvements.

Tests written after code often skip edge cases and don't verify actual behavior—they just document existing logic. TDD-first tests define requirements upfront, drive simpler designs, and guarantee testability by enforcing that production code cannot exist without a failing test.

Yes. TDD integrates with .NET and C# workflows using xUnit, NUnit, or similar test frameworks. The red-green-refactor cycle works across .NET codebases and enforces strict test naming and prohibition of production code without a failing test.

TDD requires watching each test fail before writing implementation code. This verification-first step proves the test catches real failures. If code passes a test that never failed, the test isn't verifying behavior—TDD eliminates this risk.