# Writing unit tests for undo-redo commands

### Overview

Writing unit tests for undo/redo commands is easy. The main idea to simulate a scene, execute actions and perform undo and redo. Following steps are required.

1. Create a new unit test file
2. Include the new command and the unit test file in the editor’s test suite
3. Write the test
4. Execute the test

Each of the listed steps will now be described in detail.

### 1. Create a new unit test file

Create a new file in path test/unit/editor/TestDoSomethingCommand.js.

### 2. Include the new command in the editor test suite

Navigate to the editor test suite test/unit/unittests_editor.html and open it. Within the file, go to the <!-- command object classes --> and include the new command:

// <!-- command object classes -->
//...
<script src="../../editor/js/commands/DoSomethingCommand.js"></script>         // add this line
<script src="../../editor/js/commands/MoveObjectCommand.js"></script>
//...


It is recommended to keep the script inclusions in alphabetical order, if possible.

Next, in the same file, go to <!-- Undo-Redo tests --> and include the test file for the new command:

// <!-- Undo-Redo tests -->
//...
<script src="editor/TestDoSomethingCommand.js"></script>              // add this line
<script src="editor/TestMoveObjectCommand.js"></script>
//...


Again, keeping the alphabetical order is recommended.

### 3. Write the test

#### Template

Open the unit test file test/unit/editor/TestDoSomethingCommand.js and paste following code:

module( "DoSomethingCommand" );

test("Test DoSomethingCommand (Undo and Redo)", function() {

var editor = new Editor();

var box = aBox( 'Name your box' );

// other available objects from "CommonUtilities.js"
// var sphere = aSphere( 'Name your sphere' );
// var pointLight = aPointLight( 'Name your pointLight' );
// var perspectiveCamera = aPerspectiveCamera( 'Name your perspectiveCamera' );

// in most cases you'll need to add the object to work with
editor.execute( new AddObjectCommand( editor, box ) );

} );


The predefined code is just meant to ease the development, you do not have to stick with it. However, the test should cover at least one editor.execute(), one editor.undo() and one editor.redo() call.

Best practice is to call editor.execute( new DoSomethingCommand( {custom parameters} ) ) twice. Since you’ll have to do one undo (go one step back), it is recommended to have a custom state for comparison. Try to avoid assertions ok() against default values.

#### Assertions

After performing editor.execute() twice, you can do your first assertion to check whether the executes are done correctly.

Next, you perform editor.undo() and check if the last action was undone.

Finally, perform editor.redo() and verify if the values are as expected.

### 4. Execute the test

Open the editor’s unit test suite test/unit/unittests_editor.html in your browser and check the results from the test framework.