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

# Test Contracts

> Write and run unit tests for your smart contracts

NEAR Playground includes a built-in test runner that discovers and executes your Rust tests directly in the browser.

## Test Runner Interface

The test runner opens in a dedicated modal with two panels:

* **Left Panel** - Displays discovered tests organized by file
* **Right Panel** - Shows live test output as tests execute

<Frame>
  <img src="https://mintcdn.com/nearplay/hkzsqd_V1LyMjkBt/images/guides/test-runner.png?fit=max&auto=format&n=hkzsqd_V1LyMjkBt&q=85&s=3380766e61e3bf7c3e7e25b7ad53a590" alt="Test Runner" width="4112" height="2410" data-path="images/guides/test-runner.png" />
</Frame>

## Writing Tests

Add unit tests using the standard `#[test]` attribute:

```rust theme={null}
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_default_greeting() {
        let contract = Contract::default();
        assert_eq!(contract.get_greeting(), "Hello");
    }

    #[test]
    fn test_set_greeting() {
        let mut contract = Contract::default();
        contract.set_greeting("Hi".to_string());
        assert_eq!(contract.get_greeting(), "Hi");
    }
}
```

## Running Tests

1. Click the **Tests** button in the editor toolbar
2. The Tests Modal opens showing all discovered tests
3. Click **Run All Tests** to execute all tests, or click on individual tests to run them separately
4. Watch the live output stream in the right panel
5. View pass/fail status indicators next to each test

## Test Results

After tests complete, you'll see:

| Indicator       | Meaning      |
| --------------- | ------------ |
| Green checkmark | Test passed  |
| Red X           | Test failed  |
| Spinner         | Test running |

Each test shows its execution time, and you can click on any test to see its specific output.

## Features

* **Automatic Discovery** - Tests are found by scanning for `#[test]` attributes
* **Live Streaming** - Output appears in real-time as tests run
* **Per-Test Execution** - Run all tests or select individual tests
* **Copy Output** - Copy test results to clipboard

## Tips

* Keep tests small and focused on one behavior
* Use descriptive test names that explain what's being tested
* Test both success cases and error cases
* Use `assert!`, `assert_eq!`, and `assert_ne!` macros