First Tests

The First Test

In order to start testing, you will need a directory to contain your tests. This directory will most often be in src/test, next to src/main.

For instance, if you have a class at src/main/com/github/username/, you would probably put unit tests for this class at src/test/com/github/username/

Extra Constructor

Before you can start running unit tests, your plugin will need an extra constructor. This is because the JavaPlugin class expects that the plugin was loaded by a special class loader. However, it is not possible to use this class loader during the unit test phase.

The workaround is easy though, a constructor with a visibility of protected.

public class MyPlugin extends JavaPlugin {
    public MyPlugin() {

    protected MyPlugin(JavaPluginLoader loader, PluginDescriptionFile descriptionFile, File dataFolder, File file) {
        super(loader, descriptionFile, dataFolder, file);

    public void onEnable() {
        // Executed when your plugin is enabled.

    public void onDisable() {
        // Executed when your plugin is disabled.

Creating the Test Class

Once your directories are set up, you can create unit tests like this:

public class MyPluginTests {
    private ServerMock server;
    private MyPlugin plugin;

    public void setUp() {
        // Start the mock server
        server = MockBukkit.mock();
        // Load your plugin
        plugin = MockBukkit.load(MyPlugin.class);

    public void tearDown() {
        // Stop the mock server

    public void thisTestWillFail() {
        // Perform your test


Sometimes your code may use a method that is not yet implemented in MockBukkit. When this happens MockBukkit will, instead of returning placeholder values, throw an UnimplementedOperationException. These exception extends AssumationException and will cause the test to be skipped.

These exceptions should just be ignored, though pull requests that add functionality to MockBukkit are always welcome!

As an alternative you can always extend ServerMock and implement those missing methods. Simply pass your custom implementation of ServerMock to the MockBukkit.mock(…) method.

MyCustomServerMock server = MockBukkit.mock(new MyCustomServerMock());