Back to Repositories

Testing MainThreadDisposable Implementation in ReactiveX/RxAndroid

This test suite validates the MainThreadDisposable component in RxAndroid, focusing on thread safety, disposal behavior, and state management. It ensures proper main thread verification and disposal mechanisms for Android reactive streams.

Test Coverage Overview

The test suite provides comprehensive coverage of MainThreadDisposable functionality:

Main thread verification and validation
Disposal behavior synchronization
Multiple disposal handling
Thread-specific disposal operations
Disposal state management

Edge cases include off-main-thread execution and multiple disposal attempts.

Implementation Analysis

The testing approach utilizes JUnit with Robolectric for Android environment simulation. It implements systematic verification of thread-safety mechanisms using CountDownLatch for synchronization and atomic variables for state tracking.

Key patterns include thread isolation testing, state verification, and synchronization primitives specific to Android’s main thread handling.

Technical Details

Testing tools and configuration:

JUnit test framework
Robolectric test runner
ShadowLooper for main thread manipulation
CountDownLatch for thread synchronization
AtomicBoolean and AtomicInteger for thread-safe state tracking

Best Practices Demonstrated

The test suite exemplifies high-quality testing practices:

Isolated thread testing
Proper test case organization
Comprehensive state verification
Effective use of test doubles
Clear test method naming
Proper exception handling and verification

reactivex/rxandroid

rxandroid/src/test/java/io/reactivex/rxjava3/android/MainThreadDisposableTest.java

            
/*
 * 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 io.reactivex.rxjava3.android;

import io.reactivex.rxjava3.disposables.Disposable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.robolectric.RobolectricTestRunner;
import org.robolectric.annotation.Config;
import org.robolectric.shadows.ShadowLooper;

import static java.util.concurrent.TimeUnit.SECONDS;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

@RunWith(RobolectricTestRunner.class)
@Config(manifest=Config.NONE)
public final class MainThreadDisposableTest {
  @Test public void verifyDoesNotThrowOnMainThread() throws InterruptedException {
    MainThreadDisposable.verifyMainThread();
    // Robolectric tests run on its main thread.
  }

  @Test public void verifyThrowsOffMainThread() throws InterruptedException {
    final CountDownLatch latch = new CountDownLatch(1);
    new Thread(new Runnable() {
      @Override public void run() {
        try {
          MainThreadDisposable.verifyMainThread();
          fail();
        } catch (IllegalStateException e) {
          assertTrue(e.getMessage().startsWith("Expected to be called on the main thread"));
          latch.countDown();
        }
      }
    }).start();

    assertTrue(latch.await(1, SECONDS));
  }

  @Test public void onUnsubscribeRunsSyncOnMainThread() {
    ShadowLooper.pauseMainLooper();

    final AtomicBoolean called = new AtomicBoolean();
    new MainThreadDisposable() {
      @Override protected void onDispose() {
        called.set(true);
      }
    }.dispose();

    assertTrue(called.get());
  }

  @Test public void unsubscribeTwiceDoesNotRunTwice() {
    final AtomicInteger called = new AtomicInteger(0);

    Disposable disposable = new MainThreadDisposable() {
      @Override protected void onDispose() {
        called.incrementAndGet();
      }
    };

    disposable.dispose();
    disposable.dispose();
    disposable.dispose();

    assertEquals(1, called.get());
  }

  @Test public void onUnsubscribePostsOffMainThread() throws InterruptedException {
    ShadowLooper.pauseMainLooper();

    final CountDownLatch latch = new CountDownLatch(1);
    final AtomicBoolean called = new AtomicBoolean();
    new Thread(new Runnable() {
      @Override public void run() {
        new MainThreadDisposable() {
          @Override protected void onDispose() {
            called.set(true);
          }
        }.dispose();
        latch.countDown();
      }
    }).start();

    assertTrue(latch.await(1, SECONDS));
    assertFalse(called.get()); // Callback has not yet run.

    ShadowLooper.runMainLooperOneTask();
    assertTrue(called.get());
  }

  @Test
  public void disposedState() {
    MainThreadDisposable disposable = new MainThreadDisposable() {
      @Override protected void onDispose() {
      }
    };
    assertFalse(disposable.isDisposed());
    disposable.dispose();
    assertTrue(disposable.isDisposed());
  }
}