Best Claude Code Prompt for “Write Unit Tests”
Claude Code is an agentic CLI that autonomously reads files, runs commands, and writes code. The single most important technique is verification-first prompting: start with what 'done' looks like (run tests, verify build) and describe outcomes, not implementation steps. This free template is optimized specifically for Claude Code, achieving approximately 37% token reduction compared to unoptimized prompts while producing higher quality output.
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Optimized Claude Code Prompt
<verification> Run the test suite and ensure all tests pass. Verify that the new tests cover edge cases such as empty input, invalid data types, and null values. </verification> <outcome> Write comprehensive unit tests for the provided function. The tests should accurately reflect the function's intended behavior and identify any regressions or bugs. </outcome> <context> Examine existing unit tests in the `tests/` directory to understand the established testing patterns and assertion methods. Pay close attention to the function's signature and expected return types as defined in its type annotations. </context> <constraints> Do not alter the original function's implementation. Use the existing testing framework and assertion library. Ensure tests are isolated and do not depend on external services or global state. </constraints> <git> Create a new branch for these changes. Commit the new unit tests with a clear and descriptive commit message. </git>
Why This Claude Code Prompt for “Write Unit Tests” Works Better
When you type “Write unit tests for this function” into Claude Code, it lacks structure — Claude Code has to guess what format you want, how detailed to go, and what to prioritize. The optimized version removes that guesswork.
It starts with verification criteria (what 'done' looks like), describes the desired outcome rather than implementation steps, and scopes the task to specific files — matching Claude Code's agentic workflow.
This Prompt Optimized for Other AI Models
Each AI model processes instructions differently. See how this same prompt is optimized for:
Frequently Asked Questions
What makes a good Claude Code prompt for write unit tests?
Claude Code is an agentic CLI that autonomously reads files, runs commands, and writes code. The single most important technique is verification-first prompting: start with what 'done' looks like (run tests, verify build) and describe outcomes, not implementation steps.
Can I use this prompt template for free?
Yes — copy the optimized prompt below and paste it directly into Claude Code. For unlimited prompt optimization across all 5 AI models, try PromptOptimizr free with 10 prompts per month. You can also use the Chrome extension to optimize prompts directly inside your AI chat.
Why is this prompt different from a generic one?
Each AI model processes instructions differently. Claude Code has specific formatting preferences — this prompt is structured to work with those preferences, not against them. The result is better output quality with approximately 37% fewer tokens.
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