uncoverage

⚡ Easily extract uncovered code context from Istanbul coverage reports — perfect for debugging with AI assistants like ChatGPT, Claude, or Gemini.

✨ What is this?

uncoverage is a simple CLI tool that helps you extract surrounding lines of uncovered code from Istanbul-style coverage reports (coverage-final.json).

You can quickly copy/paste context into your favorite LLM (Large Language Model) such as:

• 🧠 ChatGPT
• 🧠 Claude
• 🧠 Gemini

This is useful when you're trying to understand why something isn't covered or want help generating missing test cases.

📦 Currently supported

• ✅ Istanbul coverage format (e.g. generated by Jest, nyc, vitest)

🚀 Usage

You can run it directly with npx:

npx uncoverage coverage/coverage-final.json

or install globally:

npm install -g uncoverage
uncoverage coverage/coverage-final.json

🛠 What it does

• Parses coverage-final.json
• Finds all uncovered statements
• Groups adjacent uncovered lines (with context lines before/after)
• the grouped code context with line numbers and ← uncovered markers will be copied to your clipboard

⚙️ CLI Options

| Flag | Type | Default | Description | | ---------- | ------- | ------- | ----------------------------------------------------- | | --before | Number | 1 | Number of lines before uncovered lines to include | | --after | Number | 1 | Number of lines after uncovered lines to include | | --output | String | – | Write the output to a file (Markdown format) | | --print | Boolean | false | Print to stdout instead of copying to clipboard |

🧪 Example

npx uncoverage coverage/coverage-final.json --before 2 --after 3 --print

This will print Markdown-formatted uncovered code with 2 lines before and 3 lines after each uncovered block.

💡 Example output

## ❗ Here are the files and code blocks that are not covered by tests

### `src/utils/math.ts`

#### 🧩 Lines 42 - 45

```ts
  40: const a = 1;
  41: const b = 2;
  42: if (!user.email) return; // ← uncovered
  43: await sendWelcomeEmail(user); // ← uncovered
  44: user.notified = true; // ← uncovered
  45: return user; // ← uncovered
  46: log(user);
  47: return;

🧠 Why?

Sometimes you don’t want a full HTML coverage report — just the exact code that isn’t covered, in a form you can easily show to ChatGPT or Claude to ask:

“Can you help me write tests for this?”

That’s what uncoverage is for. 🚀

🧙‍♂️ Author

Made with 💛 by @mildronize

🧾 License

MIT