Creating guide_addingtest.md (#4388)

a proper guiding steps to add test for the root directory

Author: omsuneri

js/guide_addingtest.md

@@ -0,0 +1,110 @@
+# Test Suite Guidelines  
+
+The Music Blocks repository follows a structured approach for testing using **Jest**. All tests should be placed inside the `_tests_` directory to ensure consistency and maintainability.  
+
+## 🛠 Setting Up the Test Environment  
+
+Before running or writing tests, ensure that dependencies are installed:  
+
+```sh
+npm install
+```  
+
+To run the test suite, use:  
+
+```sh
+npm test
+```  
+
+For running tests with detailed logs:  
+
+```sh
+npm test -- --verbose
+```  
+
+## 📂 Directory Structure  
+
+```
+/musicblocks
+│── js/                 # Source code
+│── js/_tests_/         # Test directory
+│── js/utils/_tests_/   # Tests for the utils subdirectory (same format is followed for each directory)
+│── jest.config.js      # Jest configuration (try not to edit this)
+│── package.json        # Project dependencies
+│── js/guide_test.md    # This guide
+```  
+
+## 📌 Key Guidelines Before Writing Tests  
+
+### ✅ General Rules  
+- All test files **must be placed inside the `_tests_` folder of the respective directory**.  
+- Follow the naming convention: **`<filename>.test.js`**.  
+- Ensure **100% function coverage** when adding tests.  
+- **Mock dependencies** where necessary to isolate unit tests.  
+
+### 🔄 Import/Export Conventions  
+- The Music Blocks repository **strictly follows `const` for imports and exports**.  
+- **For CommonJS (`require/module.exports`)**, use:  
+
+  ```js
+  const { functionName } = require('../src/file.js');
+  ```  
+
+  Ensure `file.js` contains:  
+
+  ```js
+  if (typeof module !== 'undefined' && module.exports) {
+    module.exports = { functionName };
+  }
+  ```  
+
+### 📑 Writing Tests  
+- Use `describe` blocks to group related tests.  
+- Use `test` or `it` for defining test cases.  
+- Use **Jest matchers** like `toBe`, `toEqual`, `toHaveBeenCalled`.  
+
+#### 🔹 Example Test Structure:  
+
+```js
+const { myFunction } = require('../src/myFile.js');
+
+describe('My Function Tests', () => {
+    test('should return expected output', () => {
+        expect(myFunction()).toBe('expectedValue');
+    });
+});
+```  
+
+## 🛑 Common Mistakes to Avoid  
+❌ Making changes in the root file.  
+❌ Modifying `jest.config.js` unnecessarily.  
+❌ Placing test files **outside** `_tests_` (always keep them inside).  
+❌ Using `var` or `let` for imports (always use `const`).  
+❌ Forgetting to mock dependencies when needed.  
+❌ Not handling async tests properly (use `async/await` or `done`).  
+
+## 🚀 Running Specific Tests  
+To run a specific test file:  
+
+```sh
+npm test _tests_/filename.test.js
+```  
+
+To watch tests while coding:  
+
+```sh
+npm test -- --watch
+```  
+
+## 🔄 Updating Snapshots  
+If using Jest snapshots, update them with:  
+
+```sh
+npm test -- -u
+```  
+
+## 🎯 Contribution Guidelines  
+- Ensure all tests pass before creating a PR.  
+- Maintain code readability and add comments where needed.  
+- Adhere to the **import/export conventions** stated above.  
+- **Do not merge** without proper test coverage.