Robolectric full lifecycle of activity/fragment looper.

RobolectricTestsHelper.java

package com.tsview.robolectric;

import android.app.Activity;
import android.app.Application;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.widget.LinearLayout;

import org.junit.runner.RunWith;
import org.robolectric.Robolectric;
import org.robolectric.RobolectricTestRunner;
import org.robolectric.RuntimeEnvironment;
import org.robolectric.annotation.Config;
import org.robolectric.util.ActivityController;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/** Test holder that simplify robolectric UI tests execution. */
@Config(sdk = Build.VERSION_CODES.LOLLIPOP, manifest = "src/main/AndroidManifest.xml")
@RunWith(RobolectricTestRunner.class)
public abstract class RobolectricTestsHelper {
  /** New line delimiter. */
  public final static String NEW_LINE = "\r\n";

  /** Trace activity/fragment lifecycle states. Default: false. */
  public static final String OPTION_LIFECYCLE = "trace-lifecycle";
  /** Should log messages be with timestamp. By default: true; */
  public final static String OPTION_TIMESTAMP = "use-timestamp";
  
  /** Async Test synchronization instance. */
  public final AtomicInteger SYNC_COUNTER = new AtomicInteger();
  /** Dynamic options/configurations that influence on tests output. */
  public final Map<String, Boolean> Options = new HashMap<>();
  /** Standard Output Logger. Helps to save some useful results of tests as a part of execution. */
  private final StringBuilder mLog = new StringBuilder(64 * 1024).append(NEW_LINE);

  /**
   * Perform full lifecycle emulation for activity. When Activity is in visible state is possible to execute some
   * additional actions.
   *
   * @param onRecreate provide instance if you want to test recreation of the activity, otherwise NULL.
   */
  public <T extends Activity> ActivityController<T> fullLifecycle(
      @NonNull ActivityController<T> controller,
      @Nullable final Runnable onRestart,
      @Nullable final Runnable onResume,
      @Nullable final Runnable onVisible,
      @Nullable final RecreateRunnable<T> onRecreate) {
    Bundle savedInstanceState = null;
    final boolean doTrace = option(OPTION_LIFECYCLE, false);

    // do recreate only if defined callback
    int recreateLoops = (null != onRecreate) ? 1 : 0;
    do {
      if (doTrace) trace("state - onCreate : " + recreateLoops);
      controller.create(savedInstanceState);

      // CYCLE #1: emulate activity restart
      int lifeLoops = 1;
      do {
        if (doTrace) trace("state - onStart : " + lifeLoops);
        controller.start();

        if (null != savedInstanceState) {
          controller.restoreInstanceState(savedInstanceState);

          controller.postCreate(savedInstanceState);
        }

        // CYCLE #1.1: emulate show/hide
        int loops = 1;
        do {
          if (doTrace) trace("state - onResume : " + loops);
          if (null != onResume) onResume.run();

          controller.resume(); // --> onPostResume()

          // TODO: onAttachedToWindow()

          controller.visible(); // --> onCreateOptionsMenu(), onUserInteraction()

          if (null != onVisible) onVisible.run();

          controller.userLeaving();

          controller.pause();
          if (doTrace) trace("state - onPause");

          loops--;
        } while (loops >= 0);

        // CHECK-ME: robolectric call it before #pause()
        controller.saveInstanceState(savedInstanceState = new Bundle());

        controller.stop();
        if (doTrace) trace("state - onStop");

        // TODO: onRetainNonConfigurationInstance() --> controller.get().onRetainNonConfigurationInstance();

        // go-to onRestart() state
        if (lifeLoops > 0) {
          if (null != onRestart) onRestart.run();

          // during restart we do not need the savedInstanceState, drop the instance
          savedInstanceState = null;

          if (doTrace) trace("state - onRestart");
          controller.restart();
        }

        lifeLoops--;
      } while (lifeLoops >= 0);

      if (doTrace) trace("state - onDestroy");
      controller.destroy();

      // save instance and recover it for additional lifecycle loop
      if (recreateLoops > 0) {
        if (null != onRecreate)
          controller = onRecreate.recreate(controller);

        if (doTrace) trace("state - recreate : " + recreateLoops);
        controller.attach();
      }

      recreateLoops--;
    } while (recreateLoops >= 0);

    return controller; // can be a new instance due to re-create execution
  }

  //region --> Fragment Lifecycle emulation

  public static <T extends Fragment> ActivityController<FragmentHostingActivity> inject(
      @NonNull ActivityController<FragmentHostingActivity> controller,
      @Nullable Configure<T> configuration) {

    controller.get().setConfiguration(configuration);

    return controller;
  }

  public static <T extends Fragment> ActivityController<FragmentHostingActivity> testFragment(final Class<T> clazz) {
    return testFragment(clazz, null);
  }

  public static <T extends Fragment> ActivityController<FragmentHostingActivity> testFragment(
      @NonNull final Class<T> clazz, @Nullable final Bundle saved) {
    final Application application = RuntimeEnvironment.application;
    final Intent intent = new Intent(application, clazz);

    if (null != saved) intent.putExtras(saved);

    return testActivity(FragmentHostingActivity.class, intent);
  }
  //endregion

  //region Options

  /** Check the option. */
  public boolean option(final String name, final boolean $default) {
    if (Options.containsKey(name)) {
      return Options.get(name);
    }

    return $default;
  }

  /** Set option to a new value. */
  public void setOption(final String name, final boolean value) {
    Options.put(name, value);
  }
  //endregion

  //region Standard Output

  /** Get access to the logs memory storage directly. */
  @NonNull
  protected StringBuilder getRawLogger() {
    return mLog;
  }

  public void log(final Level level, final String tag, final String msg) {
    final long last = option(OPTION_THREAD_TIMESTAMP, true) ? mLastMsg.get() : mTimestamp;
    final String timestamp = String.format(Locale.US, " (+%-5.3f ms)", millisFrom(last));
    final boolean doTimestamp = option(OPTION_TIMESTAMP, true);

    mLog.append(level.toString().charAt(0)).append(" : ")
        .append(tag).append(" : ")
        .append(msg)
        .append(doTimestamp ? timestamp : "")
        .append(NEW_LINE);

    // update timestamps
    mLastMsg.set(mTimestamp = System.nanoTime());
  }

  /** trace single message without formatting. */
  public void trace(final String msg) {
    log(Level.INFO, "--", msg);
  }

  /** trace with formatting. */
  public void trace(final String format, final Object... args) {
    final String message = (null == args) ? format : String.format(Locale.US, format, args);

    log(Level.INFO, "--", message);
  }

  /**
   * Convert nanoseconds to milliseconds with high accuracy.
   *
   * @param nanos nanoseconds to convert.
   * @return total milliseconds.
   */
  public static double toMillis(final long nanos) {
    return nanos / 1000.0 /* micros in 1 milli */ / 1000.0 /* nanos in 1 micro */;
  }

  /** Get duration in milliseconds from start point till now. */
  public static double millisFrom(final long start) {
    return toMillis(System.nanoTime() - start);
  }
  //endregion

  //region --> Nested Declarations

  /** Implement interface for making possible testing of the activity re-creation. */
  public interface RecreateRunnable<T extends Activity> {
    ActivityController<T> recreate(final ActivityController<T> old);
  }

  /** Configure instance of the fragment before it injecting into activity. */
  public interface Configure<T extends Fragment> {
    void configure(final T instance);
  }

  /** Hosting activity that can be used for any fragment testing. */
  public static class FragmentHostingActivity extends FragmentActivity {
    /** Tag for easier finding of the fragment. */
    public static final String TAG_TEST_FRAGMENT = "TAG_TEST_FRAGMENT";

    /** Cache of the instance. */
    private Fragment mInstance;

    private Configure<Fragment> mConfiguration;

    @Override
    protected void onCreate(@Nullable final Bundle saved) {
      super.onCreate(saved);

      // first time call, otherwise restore from saved instance state should work
      if (null == saved) {
        // root view creation
        final LinearLayout view = new LinearLayout(this);
        view.setId(R.id.tag_view_holder);
        setContentView(view);

        // fragment instance creation
        final Fragment fragment = getFragmentInstantiate(getIntent());

        if (null != mConfiguration) {
          mConfiguration.configure(fragment);
        }

        // integrate fragment
        getSupportFragmentManager()
            .beginTransaction()
            .replace(R.id.tag_view_holder, fragment, TAG_TEST_FRAGMENT)
            .commit();
      }
    }

    /** Get instance of the Fragment from the fragment manager. Life instance. */
    @Nullable
    public Fragment getTestFragment() {
      return getSupportFragmentManager().findFragmentByTag(TAG_TEST_FRAGMENT);
    }

    /** Create a new instance of the Fragment based on provided intent. */
    public Fragment getFragmentInstantiate(@NonNull final Intent intent) {
      if (null != mInstance)
        return mInstance;

      final String className = intent.getComponent().getClassName();
      mInstance = Fragment.instantiate(this, className, intent.getExtras());

      return mInstance;
    }

    public void setFragmentInstantiate(final Fragment fragment) {
      mInstance = fragment;
    }

    public <T extends Fragment> FragmentHostingActivity setConfiguration(final Configure<T> configuration) {
      mConfiguration = (Configure<Fragment>) ((Configure<?>) configuration);

      return this;
    }
  }
  //endregion
}