# Test-driven Development for Active Expressions

- **Sources/Code:** nearly all relevant sources in [src/client/reactive](/src/client/reactive/)



1. Open a **Test Runner** from the context menu using `Right-Click > Tools > Test Runner`:
<br />!["test runner in the context-menu"](./test.png "test runner in the context-menu")<br />
To run all active expression-related test insert `/src/client/reactive` into the folder specification. Hitting the run button will then execute the test suite as mocha tests.
<br />![Test Runner](./test-runner.png "Test Runner")

2. Open a **Source Code Browser**
**Ctrl+Shift+B** or **Right-Click > Browse/Edit**

Saving a test file (donated by a `spec.js` or `test.js` file ending) automatically executes it in the open test runner