tdd

A test-driven development workflow for fixing bugs and adding features. It uses three steps: write a failing test, make it pass with minimal code, then clean up the code.

In plain words
What is it for?
Use it when changing TypeScript code, especially for bug fixes and new features. It covers test placement, test structure, edge cases, and running tests with Vitest.
Why use it?
It helps catch regressions by proving the expected behavior before and after a change. For bugs, the test records the failure so the fix can be checked.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/solvapay/solvapay-sdk/tdd
Clone the repo
git clone --depth 1 https://github.com/solvapay/solvapay-sdk

Made for: Cursor.

Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 350 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00017 $0.00350
Opus 5 $0.00009 $0.00175
Sonnet 5 $0.00003 $0.00070
Haiku 4.5 $0.00002 $0.00035

Measured 2d ago against content hash 4b9dbe6c293f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

tdd scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/tdd.mdc · 47 lines

What it actually says

Test-Driven Development

Use RED-GREEN-REFACTOR for all bug fixes and new features.

Workflow

  1. RED -- Write a failing test that describes the expected behavior
  2. GREEN -- Write the minimal code to make the test pass
  3. REFACTOR -- Clean up the implementation while keeping tests green

Bug Fixes

Always write a test that reproduces the bug before writing the fix:

  1. Write a test that fails because of the bug
  2. Run the test to confirm it fails
  3. Fix the bug with minimal changes
  4. Run the test again to confirm it passes
  5. Refactor if needed

New Features

Write tests for the expected behavior before implementing:

  1. Define the expected inputs and outputs
  2. Write tests covering the happy path and key edge cases
  3. Implement until all tests pass
  4. Refactor the implementation

Test Structure

  • Co-locate tests: *.test.ts next to the source file
  • One behavior per test: each it() should test a single expectation
  • Descriptive names: it('should throw when API key is missing')
  • Arrange-Act-Assert: set up data, call the function, check the result

Running Tests

  • npx vitest run <path> -- run a single test file
  • npx vitest --watch -- run tests in watch mode
  • npx vitest run -- run all tests
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 47 lines · 17 tokens per session scan A 4b9dbe6c293f

Subscribe to this mod's changes

tdd is a cursor rule published in the GitHub repository solvapay/solvapay-sdk (5 stars, last pushed 2d ago), licensed MIT. It adds 17 tokens to every session and 350 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.