Skip to main content
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
Test Runner

​
Writing Tests

Add unit tests using the standard #[test] attribute: 
#[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:
IndicatorMeaning
Green checkmarkTest passed
Red XTest failed
SpinnerTest 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