MockingBinder.java

/*
 * Copyright 2011 ArcBees Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package com.gwtplatform.tester;

import java.lang.reflect.Field;

import com.google.gwt.uibinder.client.UiBinder;
import com.google.gwt.uibinder.client.UiField;

/**
 * {@link MockingBinder} makes testing view even easier by mocking every {@link UiField} and returning a mocked object
 * upon creation.
 * <p/>
 * To use it, you should build a small class that extends MockingBinder and bind that class inside your Guice test
 * module. You will have to provide a {@link MockFactory} to let MockingBinder mock everything.
 * <p/>
 * Ex:
 * <pre>
 * public static class Module extends JukitoModule {
 *  static class MyTestBinder extends MockingBinder<Widget, BlogView> implements
 *  Binder {
 *    public MyTestBinder(final AnyMockFactory anyMockFactory) {
 *      super(Widget.class, anyMockFactory);
 *    }
 *  }
 *
 *  protected void configureTest() {
 *    GWTMockUtilities.disarm();
 *
 *    bind(Binder.class).to(MyTestBinder.class);
 *  }
 * }
 * </pre>
 * <p/>
 * Disarming GWT is important to unit test views.
 *
 * @param <U> Mock type returned by {@link UiBinder#createAndBindUi(Object)}.
 * @param <O> Owner type.
 */
public abstract class MockingBinder<U, O> implements UiBinder<U, O> {
    private final Class<U> returnTypeClass;
    private final MockFactory mockFactory;

    /**
     * @param returnTypeClass Type to return when creating the mocked ui.
     * @param mockFactory A {@link MockFactory} to provide mock object.
     */
    public MockingBinder(
            Class<U> returnTypeClass,
            MockFactory mockFactory) {
        this.returnTypeClass = returnTypeClass;
        this.mockFactory = mockFactory;
    }

    @Override
    public U createAndBindUi(O owner) throws IllegalArgumentException {
        Field[] fields = owner.getClass().getDeclaredFields();

        for (Field field : fields) {
            field.setAccessible(true);

            if (field.isAnnotationPresent(UiField.class)) {
                Object mockObject = mockFactory.mock(field.getType());

                try {
                    field.set(owner, mockObject);
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                    throw new RuntimeException(e);
                }
            }
        }

        return mockFactory.mock(returnTypeClass);
    }
}