> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cow.bleu.builders/llms.txt
> Use this file to discover all available pages before exploring further.

# Testing

> Testing guide for CoW Protocol smart contracts using Hardhat and Waffle

# Testing

A comprehensive testing guide for the CoW Protocol smart contracts project, covering test execution, debugging, gas reporting, and code coverage analysis.

## Test Framework

Tests leverage:

* **Hardhat** - Development environment
* **Waffle** - Smart contract testing library
* **Chai** - Assertion library
* **ethers.js** - Ethereum interaction library

## Running Tests

### Standard Suite

Run the complete test battery:

```bash theme={null}
yarn test
```

### Excluded Tests

Execute tests that skip coverage analysis:

```bash theme={null}
yarn test:ignored-in-coverage
```

### Coverage Reports

Generate detailed instrumentation metrics:

```bash theme={null}
yarn coverage
```

## Debugging

Enable verbose output to track contract deployments, transaction details, state changes, and event emissions:

```bash theme={null}
DEBUG=* yarn test
```

## Gas Reporting

Activate gas tracking to produce consumption tables showing costs per operation and deployment expenses:

```bash theme={null}
REPORT_GAS=1 yarn test
```

## Coverage Analysis

The `yarn coverage` command instruments contracts and generates:

* **Terminal summary** with coverage percentages
* **Interactive HTML report** at `coverage/index.html`

### Coverage Color Coding

| Color  | Meaning          |
| ------ | ---------------- |
| Red    | Uncovered lines  |
| Yellow | Partial coverage |
| Green  | Fully covered    |

<Warning>
  Coverage instrumentation alters bytecode, making it unsuitable for gas benchmarking. Do not use coverage reports for gas analysis.
</Warning>

## Configuration

The `MOCHA_CONF` environment variable controls test scope across different execution contexts:

```bash theme={null}
MOCHA_CONF=custom yarn test
```

## Troubleshooting

| Issue                                | Solution                                                                |
| ------------------------------------ | ----------------------------------------------------------------------- |
| Test failures after contract changes | Rebuild with `yarn build:sol`                                           |
| Cached state issues                  | Clear Hardhat cache: `rm -rf cache/`                                    |
| Memory errors during coverage        | Increase heap: `NODE_OPTIONS="--max-old-space-size=4096" yarn coverage` |