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Testing EventBus Main Thread Operations in greenrobot/EventBus

This test suite validates EventBus main thread event handling and message delivery in Android applications. It ensures proper event posting and thread management for both main thread and background thread scenarios.

Test Coverage Overview

The test suite covers core EventBus functionality for main thread operations.

Direct event posting validation on main thread
Background thread to main thread event delivery
Event subscription with ThreadMode.MAIN verification
Thread context verification using Android Looper

Implementation Analysis

The testing approach utilizes JUnit framework with Android-specific components to validate EventBus threading behavior.

Key implementation patterns include:

Background thread simulation using TestBackgroundPoster
Event tracking with timing constraints
Thread context validation using Looper comparison
Annotation-based subscription handling

Technical Details

Testing infrastructure includes:

JUnit test framework
Android Looper for thread management
Custom AbstractAndroidEventBusTest base class
Event tracking mechanisms with timing controls
Background thread simulation utilities

Best Practices Demonstrated

The test suite exemplifies high-quality testing practices for event-driven systems.

Proper test isolation and cleanup
Explicit thread context verification
Timeout handling for async operations
Clear test case organization
Comprehensive threading scenario coverage

greenrobot/eventbus

EventBusTest/src/org/greenrobot/eventbus/EventBusMainThreadTest.java

            
/*
 * Copyright (C) 2012-2016 Markus Junginger, greenrobot (http://greenrobot.org)
 *
 * 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 org.greenrobot.eventbus;

import android.os.Looper;

import org.junit.Test;


import static org.junit.Assert.assertEquals;

/**
 * @author Markus Junginger, greenrobot
 */
public class EventBusMainThreadTest extends AbstractAndroidEventBusTest {

    @Test
    public void testPost() throws InterruptedException {
        eventBus.register(this);
        eventBus.post("Hello");
        waitForEventCount(1, 1000);

        assertEquals("Hello", lastEvent);
        assertEquals(Looper.getMainLooper().getThread(), lastThread);
    }

    @Test
    public void testPostInBackgroundThread() throws InterruptedException {
        TestBackgroundPoster backgroundPoster = new TestBackgroundPoster(eventBus);
        backgroundPoster.start();

        eventBus.register(this);
        backgroundPoster.post("Hello");
        waitForEventCount(1, 1000);
        assertEquals("Hello", lastEvent);
        assertEquals(Looper.getMainLooper().getThread(), lastThread);

        backgroundPoster.shutdown();
        backgroundPoster.join();
    }

    @Subscribe(threadMode = ThreadMode.MAIN)
    public void onEventMainThread(String event) {
        trackEvent(event);
    }

}