services/tests/mockingservicestests/src/com/android/server/pm/UserVisibilityMediatorTestCase.java

/*
 * Copyright (C) 2022 The Android Open Source Project
 *
 * 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.android.server.pm;

import static android.os.UserHandle.USER_ALL;
import static android.os.UserHandle.USER_CURRENT;
import static android.os.UserHandle.USER_CURRENT_OR_SELF;
import static android.os.UserHandle.USER_NULL;
import static android.os.UserHandle.USER_SYSTEM;
import static android.view.Display.DEFAULT_DISPLAY;
import static android.view.Display.INVALID_DISPLAY;

import static com.android.server.pm.UserManagerInternal.USER_ASSIGNMENT_RESULT_FAILURE;
import static com.android.server.pm.UserManagerInternal.USER_ASSIGNMENT_RESULT_SUCCESS_INVISIBLE;
import static com.android.server.pm.UserManagerInternal.USER_ASSIGNMENT_RESULT_SUCCESS_VISIBLE;
import static com.android.server.pm.UserManagerInternal.USER_START_MODE_BACKGROUND;
import static com.android.server.pm.UserManagerInternal.USER_START_MODE_BACKGROUND_VISIBLE;
import static com.android.server.pm.UserManagerInternal.USER_START_MODE_FOREGROUND;
import static com.android.server.pm.UserManagerInternal.userAssignmentResultToString;
import static com.android.server.pm.UserVisibilityChangedEvent.onInvisible;
import static com.android.server.pm.UserVisibilityChangedEvent.onVisible;
import static com.android.server.pm.UserVisibilityMediator.INITIAL_CURRENT_USER_ID;

import static com.google.common.truth.Truth.assertWithMessage;

import static org.junit.Assert.assertThrows;

import android.annotation.UserIdInt;
import android.os.Handler;
import android.text.TextUtils;
import android.util.IntArray;
import android.util.Log;

import com.android.server.DumpableDumperRule;
import com.android.server.ExpectableTestCase;

import org.junit.Before;
import org.junit.Test;

import java.util.Arrays;

/**
 * Base class for {@link UserVisibilityMediator} tests.
 *
 * <p>It contains common logics and tests for behaviors that should be invariant regardless of the
 * device mode (for example, whether the device supports concurrent multiple users on multiple
 * displays or not).
 *
 * <p><P>NOTE: <p> rather than adopting the "one test case for method approach", this class (and
 * its subclass) adds "one test case for scenario" approach, so it can test many properties (if user
 * is visible, display associated to the user, etc...) for each scenario (full user started on fg,
 * profile user started on bg, etc...).
 */
abstract class UserVisibilityMediatorTestCase extends ExpectableTestCase {

    private static final String TAG = UserVisibilityMediatorTestCase.class.getSimpleName();

    /**
     * Id for a simple user (that doesn't have profiles).
     */
    protected static final int USER_ID = 600;

    /**
     * Id for another simple user.
     */
    protected static final int OTHER_USER_ID = 666;

    /**
     * Id for yeat another simple user.
     */
    protected static final int YET_ANOTHER_USER_ID = 700;

    /**
     * Id for a user that has one profile (whose id is {@link #PROFILE_USER_ID}.
     *
     * <p>You can use {@link #addDefaultProfileAndParent()} to add both of this user to the service.
     */
    protected static final int PARENT_USER_ID = 642;

    /**
     * Id for a profile whose parent is {@link #PARENTUSER_ID}.
     *
     * <p>You can use {@link #addDefaultProfileAndParent()} to add both of this user to the service.
     */
    protected static final int PROFILE_USER_ID = 643;

    /**
     * Id of a secondary display (i.e, not {@link android.view.Display.DEFAULT_DISPLAY}).
     */
    protected static final int SECONDARY_DISPLAY_ID = 42;

    /**
     * Id of another secondary display (i.e, not {@link android.view.Display.DEFAULT_DISPLAY}).
     */
    protected static final int OTHER_SECONDARY_DISPLAY_ID = 108;

    protected static final int FG = USER_START_MODE_FOREGROUND;
    protected static final int BG = USER_START_MODE_BACKGROUND;
    protected static final int BG_VISIBLE = USER_START_MODE_BACKGROUND_VISIBLE;

    private Handler mHandler;
    protected AsyncUserVisibilityListener.Factory mListenerFactory;

    private final boolean mBackgroundUsersOnDisplaysEnabled;
    private final boolean mBackgroundUserOnDefaultDisplayAllowed;

    protected UserVisibilityMediator mMediator;

    protected UserVisibilityMediatorTestCase(boolean backgroundUsersOnDisplaysEnabled,
            boolean backgroundUserOnDefaultDisplayAllowed) {
        mBackgroundUsersOnDisplaysEnabled = backgroundUsersOnDisplaysEnabled;
        mBackgroundUserOnDefaultDisplayAllowed = backgroundUserOnDefaultDisplayAllowed;
    }

    protected final DumpableDumperRule mDumpableDumperRule = new DumpableDumperRule();

    @Before
    public final void setFixtures() {
        mHandler = Handler.getMain();
        Thread thread = mHandler.getLooper().getThread();
        Log.i(TAG, "setFixtures(): using thread " + thread + " (from handler " + mHandler + ")");
        mListenerFactory = new AsyncUserVisibilityListener.Factory(mExpect, thread);
        mMediator = new UserVisibilityMediator(mBackgroundUsersOnDisplaysEnabled,
                mBackgroundUserOnDefaultDisplayAllowed, mHandler);
        mDumpableDumperRule.addDumpable(mMediator);
    }

    @Test
    public void testInvalidMode() {
        assertThrows(IllegalArgumentException.class, () -> new UserVisibilityMediator(
                /* visibleBackgroundUsersOnDisplaysEnabled= */ false,
                /* visibleBackgroundUserOnDefaultDisplayAllowed= */ true, mHandler));
    }

    @Test
    public final void testAssignUserToDisplayOnStart_invalidUserIds() {
        assertThrows(IllegalArgumentException.class, () -> mMediator
                .assignUserToDisplayOnStart(USER_NULL, USER_ID, FG, DEFAULT_DISPLAY));
        assertThrows(IllegalArgumentException.class, () -> mMediator
                .assignUserToDisplayOnStart(USER_ALL, USER_ID, FG, DEFAULT_DISPLAY));
        assertThrows(IllegalArgumentException.class, () -> mMediator
                .assignUserToDisplayOnStart(USER_CURRENT, USER_ID, FG, DEFAULT_DISPLAY));
        assertThrows(IllegalArgumentException.class, () -> mMediator
                .assignUserToDisplayOnStart(USER_CURRENT_OR_SELF, USER_ID, FG, DEFAULT_DISPLAY));
    }

    @Test
    public final void testAssignUserToDisplayOnStart_invalidUserStartMode() {
        assertThrows(IllegalArgumentException.class, () -> mMediator
                .assignUserToDisplayOnStart(USER_ID, USER_ID, 666, DEFAULT_DISPLAY));
    }

    @Test
    public final void testStartFgUser_onSecondaryDisplay() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result =
                mMediator.assignUserToDisplayOnStart(USER_ID, USER_ID, FG, SECONDARY_DISPLAY_ID);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(USER_ID);
        expectNoDisplayAssignedToUser(USER_ID);
        expectInitialCurrentUserAssignedToDisplay(DEFAULT_DISPLAY);

        listener.verify();
    }

    @Test
    public final void testStartBgUser_onDefaultDisplay() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(USER_ID, USER_ID, BG, DEFAULT_DISPLAY);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_SUCCESS_INVISIBLE);

        expectUserIsNotVisibleAtAll(USER_ID);
        expectNoDisplayAssignedToUser(USER_ID);
        expectInitialCurrentUserAssignedToDisplay(DEFAULT_DISPLAY);

        assertInvisibleUserCannotBeAssignedExtraDisplay(USER_ID, SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    protected final @UserIdInt int visibleBgUserCannotBeStartedOnDefaultDisplayTest()
            throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(USER_ID, USER_ID, BG_VISIBLE,
                DEFAULT_DISPLAY);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(USER_ID);
        expectNoDisplayAssignedToUser(USER_ID);

        listener.verify();

        return USER_ID;
    }

    @Test
    public final void testStartBgUser_onSecondaryDisplay() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(USER_ID, USER_ID, BG,
                SECONDARY_DISPLAY_ID);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(USER_ID);
        expectNoDisplayAssignedToUser(USER_ID);

        assertInvisibleUserCannotBeAssignedExtraDisplay(USER_ID, SECONDARY_DISPLAY_ID);
        assertInvisibleUserCannotBeAssignedExtraDisplay(USER_ID, OTHER_SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    @Test
    public final void testStartBgSystemUser_onSecondaryDisplay() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForEvents(
                onInvisible(INITIAL_CURRENT_USER_ID),
                onVisible(USER_ID));
        // Must explicitly set current user, as USER_SYSTEM is the default current user
        startForegroundUser(USER_ID);

        int result = mMediator.assignUserToDisplayOnStart(USER_SYSTEM, USER_SYSTEM, BG,
                SECONDARY_DISPLAY_ID);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(USER_SYSTEM);

        expectNoDisplayAssignedToUser(USER_SYSTEM);
        expectUserAssignedToDisplay(SECONDARY_DISPLAY_ID, USER_ID);

        assertUserCannotBeAssignedExtraDisplay(USER_SYSTEM, SECONDARY_DISPLAY_ID);
        assertUserCannotBeAssignedExtraDisplay(USER_SYSTEM, OTHER_SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    @Test
    public final void testStopVisibleBgProfile() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForEvents(
                onInvisible(INITIAL_CURRENT_USER_ID),
                onVisible(PARENT_USER_ID),
                onVisible(PROFILE_USER_ID),
                onInvisible(PROFILE_USER_ID));
        startDefaultProfile();

        mMediator.unassignUserFromDisplayOnStop(PROFILE_USER_ID);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);
        expectNoDisplayAssignedToUser(PROFILE_USER_ID);
        expectUserAssignedToDisplay(DEFAULT_DISPLAY, PARENT_USER_ID);

        listener.verify();
    }

    @Test
    public final void testVisibleBgProfileBecomesInvisibleWhenParentIsSwitchedOut()
            throws Exception {
        AsyncUserVisibilityListener listener = addListenerForEvents(
                onInvisible(INITIAL_CURRENT_USER_ID),
                onVisible(PARENT_USER_ID),
                onVisible(PROFILE_USER_ID),
                onInvisible(PARENT_USER_ID),
                onInvisible(PROFILE_USER_ID),
                onVisible(OTHER_USER_ID));
        startDefaultProfile();

        startForegroundUser(OTHER_USER_ID);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);
        expectNoDisplayAssignedToUser(PROFILE_USER_ID);
        expectUserAssignedToDisplay(DEFAULT_DISPLAY, OTHER_USER_ID);

        assertUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID, SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    @Test
    public final void testStartVisibleBgProfile_onDefaultDisplay_whenParentIsNotStarted()
            throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID,
                BG_VISIBLE, DEFAULT_DISPLAY);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);
        expectNoDisplayAssignedToUser(PROFILE_USER_ID);

        listener.verify();
    }

    @Test
    public final void testStartVisibleBgProfile_onDefaultDisplay_whenParentIsStartedOnBg()
            throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();
        startBackgroundUser(PARENT_USER_ID);

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID,
                BG_VISIBLE, DEFAULT_DISPLAY);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);

        expectNoDisplayAssignedToUser(PROFILE_USER_ID);
        expectInitialCurrentUserAssignedToDisplay(DEFAULT_DISPLAY);

        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID, SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    // Not supported - profiles can only be started on default display
    @Test
    public final void testStartVisibleBgProfile_onSecondaryDisplay() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID,
                BG_VISIBLE, SECONDARY_DISPLAY_ID);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);
        expectNoDisplayAssignedToUser(PROFILE_USER_ID);
        expectInitialCurrentUserAssignedToDisplay(SECONDARY_DISPLAY_ID);

        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID, SECONDARY_DISPLAY_ID);
        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID,
                OTHER_SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    @Test
    public final void testStartBgProfile_onDefaultDisplay_whenParentIsNotStarted()
            throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID, BG,
                DEFAULT_DISPLAY);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_SUCCESS_INVISIBLE);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);
        expectNoDisplayAssignedToUser(PROFILE_USER_ID);

        listener.verify();
    }

    @Test
    public final void testStartBgProfile_onDefaultDisplay_whenParentIsStartedOnBg()
            throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();
        startBackgroundUser(PARENT_USER_ID);

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID, BG,
                DEFAULT_DISPLAY);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_SUCCESS_INVISIBLE);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);

        expectNoDisplayAssignedToUser(PROFILE_USER_ID);
        expectInitialCurrentUserAssignedToDisplay(DEFAULT_DISPLAY);

        assertUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID, SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    @Test
    public final void testStartBgProfile_onSecondaryDisplay() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID, BG,
                SECONDARY_DISPLAY_ID);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);
        expectNoDisplayAssignedToUser(PROFILE_USER_ID);
        expectInitialCurrentUserAssignedToDisplay(SECONDARY_DISPLAY_ID);

        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID, SECONDARY_DISPLAY_ID);
        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID,
                OTHER_SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    @Test
    public final void testStartFgProfile_onDefaultDisplay() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID, FG,
                DEFAULT_DISPLAY);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);

        expectNoDisplayAssignedToUser(PROFILE_USER_ID);
        expectInitialCurrentUserAssignedToDisplay(DEFAULT_DISPLAY);

        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID, DEFAULT_DISPLAY);
        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID, SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    @Test
    public final void testStartFgProfile_onSecondaryDisplay() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID, FG,
                SECONDARY_DISPLAY_ID);
        assertStartUserResult(result, USER_ASSIGNMENT_RESULT_FAILURE);

        expectUserIsNotVisibleAtAll(PROFILE_USER_ID);
        expectNoDisplayAssignedToUser(PROFILE_USER_ID);
        expectInitialCurrentUserAssignedToDisplay(SECONDARY_DISPLAY_ID);

        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID, SECONDARY_DISPLAY_ID);
        assertInvisibleUserCannotBeAssignedExtraDisplay(PROFILE_USER_ID,
                OTHER_SECONDARY_DISPLAY_ID);

        listener.verify();
    }

    @Test
    public final void testIsUserVisible_invalidUsers() throws Exception {
        expectWithMessage("isUserVisible(%s)", USER_NULL)
                .that(mMediator.isUserVisible(USER_NULL))
                .isFalse();
        expectWithMessage("isUserVisible(%s)", USER_NULL)
                .that(mMediator.isUserVisible(USER_ALL))
                .isFalse();
        expectWithMessage("isUserVisible(%s)", USER_NULL)
                .that(mMediator.isUserVisible(USER_CURRENT))
                .isFalse();
        expectWithMessage("isUserVisible(%s)", USER_NULL)
                .that(mMediator.isUserVisible(USER_CURRENT_OR_SELF))
                .isFalse();
    }

    @Test
    public final void testRemoveListener() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForNoEvents();

        mMediator.removeListener(listener);

        startForegroundUser(USER_ID);
        listener.verify();
    }

    @Test
    public final void testOnSystemUserVisibilityChanged() throws Exception {
        AsyncUserVisibilityListener listener = addListenerForEvents(onVisible(USER_SYSTEM));

        mMediator.onSystemUserVisibilityChanged(/* visible= */ true);

        listener.verify();
    }

    /**
     * Starts a user in foreground on the default display, asserting it was properly started.
     *
     * <p><b>NOTE: </b>should only be used as a helper method, not to test the behavior of the
     * {@link UserVisibilityMediator#assignUserToDisplayOnStart(int, int, boolean, int)} method per
     * se.
     */
    protected void startForegroundUser(@UserIdInt int userId) {
        Log.d(TAG, "startForegroundUSer(" + userId + ")");
        int result = mMediator.assignUserToDisplayOnStart(userId, userId, FG, DEFAULT_DISPLAY);
        if (result != USER_ASSIGNMENT_RESULT_SUCCESS_VISIBLE) {
            throw new IllegalStateException("Failed to start foreground user " + userId
                    + ": mediator returned " + userAssignmentResultToString(result));
        }
    }

    /**
     * Starts a user in background on the default display, asserting it was properly started.
     *
     * <p><b>NOTE: </b>should only be used as a helper method, not to test the behavior of the
     * {@link UserVisibilityMediator#assignUserToDisplayOnStart(int, int, boolean, int)} method per
     * se.
     */
    protected void startBackgroundUser(@UserIdInt int userId) {
        Log.d(TAG, "startBackgroundUser(" + userId + ")");
        int result = mMediator.assignUserToDisplayOnStart(userId, userId, BG, DEFAULT_DISPLAY);
        if (result != USER_ASSIGNMENT_RESULT_SUCCESS_INVISIBLE) {
            throw new IllegalStateException("Failed to start background user " + userId
                    + ": mediator returned " + userAssignmentResultToString(result));
        }
    }

    /**
     * Starts the {@link #PROFILE_USER_ID default profile} in background and its
     * {@link #PARENT_USER_ID parent} in foreground on the main display, asserting that
     * both were properly started.
     *
     * <p><b>NOTE: </b>should only be used as a helper method, not to test the behavior of the
     * {@link UserVisibilityMediator#assignUserToDisplayOnStart(int, int, boolean, int)} method per
     * se.
     */
    protected void startDefaultProfile() {
        startForegroundUser(PARENT_USER_ID);
        Log.d(TAG, "starting default profile (" + PROFILE_USER_ID + ") in background after starting"
                + " its parent (" + PARENT_USER_ID + ") on foreground");

        int result = mMediator.assignUserToDisplayOnStart(PROFILE_USER_ID, PARENT_USER_ID,
                BG_VISIBLE, DEFAULT_DISPLAY);
        if (result != USER_ASSIGNMENT_RESULT_SUCCESS_VISIBLE) {
            throw new IllegalStateException("Failed to start profile user " + PROFILE_USER_ID
                    + ": mediator returned " + userAssignmentResultToString(result));
        }
    }

    /**
     * Starts a user in background on the secondary display, asserting it was properly started.
     *
     * <p><b>NOTE: </b>should only be used as a helper method, not to test the behavior of the
     * {@link UserVisibilityMediator#assignUserToDisplayOnStart(int, int, boolean, int)} method per
     * se.
     */
    protected final void startUserInSecondaryDisplay(@UserIdInt int userId, int displayId) {
        Log.d(TAG, "startUserInSecondaryDisplay(" + userId + ", " + displayId + ")");
        int result = mMediator.assignUserToDisplayOnStart(userId, userId, BG_VISIBLE, displayId);
        if (result != USER_ASSIGNMENT_RESULT_SUCCESS_VISIBLE) {
            throw new IllegalStateException("Failed to startuser " + userId
                    + " on background: mediator returned " + userAssignmentResultToString(result));
        }
    }

    protected AsyncUserVisibilityListener addListenerForNoEvents() {
        AsyncUserVisibilityListener listener = mListenerFactory.forNoEvents();
        mMediator.addListener(listener);
        return listener;
    }

    protected AsyncUserVisibilityListener addListenerForEvents(
            UserVisibilityChangedEvent... events) {
        AsyncUserVisibilityListener listener = mListenerFactory.forEvents(events);
        mMediator.addListener(listener);
        return listener;
    }

    protected void assertStartUserResult(int actualResult, int expectedResult) {
        assertStartUserResult(actualResult, expectedResult, "");
    }

    @SuppressWarnings("AnnotateFormatMethod")
    protected void assertStartUserResult(int actualResult, int expectedResult,
            String extraMessageFormat, Object... extraMessageArguments) {
        String extraMessage = String.format(extraMessageFormat, extraMessageArguments);
        assertWithMessage("startUser() result %s(where %s=%s and %s=%s)", extraMessage,
                expectedResult, userAssignmentResultToString(expectedResult),
                actualResult, userAssignmentResultToString(actualResult))
                        .that(actualResult).isEqualTo(expectedResult);
    }

    protected void assertBgUserBecomesInvisibleOnStop(@UserIdInt int userId) {
        Log.d(TAG, "Stopping user " + userId);
        mMediator.unassignUserFromDisplayOnStop(userId);
        expectUserIsNotVisibleAtAll(userId);
    }

    /**
     * Assigns and unassigns the user to / from an extra display, asserting the visibility state in
     * between.
     *
     * <p>It assumes the user was not visible in the display beforehand.
     */
    protected void assertUserCanBeAssignedExtraDisplay(@UserIdInt int userId, int displayId) {
        assertUserCanBeAssignedExtraDisplay(userId, displayId, /* unassign= */ true);
    }

    protected void assertUserCanBeAssignedExtraDisplay(@UserIdInt int userId, int displayId,
            boolean unassign) {

        expectUserIsNotVisibleOnDisplay(userId, displayId);

        Log.d(TAG, "Calling assignUserToExtraDisplay(" + userId + ", " + displayId + ")");
        assertWithMessage("assignUserToExtraDisplay(%s, %s)", userId, displayId)
                .that(mMediator.assignUserToExtraDisplay(userId, displayId))
                .isTrue();
        expectUserIsVisibleOnDisplay(userId, displayId);
        expectDisplaysAssignedToUserContainsDisplayId(userId, displayId);

        if (unassign) {
            Log.d(TAG, "Calling unassignUserFromExtraDisplay(" + userId + ", " + displayId + ")");
            assertWithMessage("unassignUserFromExtraDisplay(%s, %s)", userId, displayId)
                    .that(mMediator.unassignUserFromExtraDisplay(userId, displayId))
                    .isTrue();
            expectUserIsNotVisibleOnDisplay(userId, displayId);
            expectDisplaysAssignedToUserDoesNotContainDisplayId(userId, displayId);
        }
    }

    /**
     * Asserts that a user (already visible or not) cannot be assigned to an extra display (and
     * hence won't be visible on that display).
     */
    protected void assertUserCannotBeAssignedExtraDisplay(@UserIdInt int userId, int displayId) {
        expectWithMessage("assignUserToExtraDisplay(%s, %s)", userId, displayId)
                .that(mMediator.assignUserToExtraDisplay(userId, displayId))
                .isFalse();
        expectUserIsNotVisibleOnDisplay(userId, displayId);
    }

    /**
     * Asserts that an invisible user cannot be assigned to an extra display.
     */
    protected void assertInvisibleUserCannotBeAssignedExtraDisplay(@UserIdInt int userId,
            int displayId) {
        assertUserCannotBeAssignedExtraDisplay(userId, displayId);
        expectNoDisplayAssignedToUser(userId);
        expectInitialCurrentUserAssignedToDisplay(displayId);
    }

    protected void expectUserIsVisible(@UserIdInt int userId) {
        expectWithMessage("isUserVisible(%s)", userId)
                .that(mMediator.isUserVisible(userId))
                .isTrue();
    }

    protected void expectVisibleUsers(@UserIdInt Integer... userIds) {
        IntArray visibleUsers = mMediator.getVisibleUsers();
        expectWithMessage("getVisibleUsers()").that(visibleUsers).isNotNull();
        expectWithMessage("getVisibleUsers()").that(visibleUsers.toArray()).asList()
                .containsExactlyElementsIn(Arrays.asList(userIds));
    }

    protected void expectUserIsVisibleOnDisplay(@UserIdInt int userId, int displayId) {
        expectWithMessage("isUserVisible(%s, %s)", userId, displayId)
                .that(mMediator.isUserVisible(userId, displayId))
                .isTrue();
    }

    protected void expectUserIsNotVisibleOnDisplay(@UserIdInt int userId, int displayId) {
        expectWithMessage("isUserVisible(%s, %s)", userId, displayId)
                .that(mMediator.isUserVisible(userId, displayId))
                .isFalse();
    }

    protected void expectUserIsNotVisibleOnDisplay(String when, @UserIdInt int userId,
            int displayId) {
        String suffix = TextUtils.isEmpty(when) ? "" : " on " + when;
        expectWithMessage("isUserVisible(%s, %s)%s", userId, displayId, suffix)
                .that(mMediator.isUserVisible(userId, displayId))
                .isFalse();
    }

    protected void expectUserIsNotVisibleAtAll(@UserIdInt int userId) {
        expectWithMessage("isUserVisible(%s)", userId)
                .that(mMediator.isUserVisible(userId))
                .isFalse();
        expectUserIsNotVisibleOnDisplay(userId, DEFAULT_DISPLAY);
        expectUserIsNotVisibleOnDisplay(userId, INVALID_DISPLAY);
        expectUserIsNotVisibleOnDisplay(userId, SECONDARY_DISPLAY_ID);
        expectUserIsNotVisibleOnDisplay(userId, OTHER_SECONDARY_DISPLAY_ID);
        expectDisplaysAssignedToUserIsEmpty(userId);
    }

    protected void expectDisplayAssignedToUser(@UserIdInt int userId, int displayId) {
        expectWithMessage("getDisplayAssignedToUser(%s)", userId)
                .that(mMediator.getDisplayAssignedToUser(userId)).isEqualTo(displayId);
    }

    protected void expectNoDisplayAssignedToUser(@UserIdInt int userId) {
        expectWithMessage("getDisplayAssignedToUser(%s)", userId)
                .that(mMediator.getDisplayAssignedToUser(userId)).isEqualTo(INVALID_DISPLAY);
    }

    protected void expectDisplaysAssignedToUserContainsDisplayId(
            @UserIdInt int userId, int displayId) {
        expectWithMessage("getDisplaysAssignedToUser(%s)", userId)
                .that(mMediator.getDisplaysAssignedToUser(userId)).asList().contains(displayId);
    }

    protected void expectDisplaysAssignedToUserDoesNotContainDisplayId(
            @UserIdInt int userId, int displayId) {
        expectWithMessage("getDisplaysAssignedToUser(%s)", userId)
                .that(mMediator.getDisplaysAssignedToUser(userId)).asList()
                .doesNotContain(displayId);
    }

    protected void expectDisplaysAssignedToUserIsEmpty(@UserIdInt int userId) {
        expectWithMessage("getDisplaysAssignedToUser(%s)", userId)
                .that(mMediator.getDisplaysAssignedToUser(userId)).isNull();
    }

    protected void expectUserCannotBeUnassignedFromDisplay(@UserIdInt int userId, int displayId) {
        expectWithMessage("unassignUserFromExtraDisplay(%s, %s)", userId, displayId)
                .that(mMediator.unassignUserFromExtraDisplay(userId, displayId)).isFalse();
    }

    protected void expectUserAssignedToDisplay(int displayId, @UserIdInt int userId) {
        expectWithMessage("getUserAssignedToDisplay(%s)", displayId)
                .that(mMediator.getUserAssignedToDisplay(displayId)).isEqualTo(userId);
    }

    protected void expectInitialCurrentUserAssignedToDisplay(int displayId) {
        expectWithMessage("getUserAssignedToDisplay(%s)", displayId)
                .that(mMediator.getUserAssignedToDisplay(displayId))
                .isEqualTo(INITIAL_CURRENT_USER_ID);
    }
}