Enable button only when scrollview reached the bottom

Bug: 28410288
Test: make RunSettingsRoboTests
Change-Id: I04653c377f7d419b6701b5589ff25961e0f5c077

tests/robotests/src/com/android/settings/MasterClearTest.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2016 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.settings;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.when;
+
+import android.widget.LinearLayout;
+import android.widget.ScrollView;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.annotation.Config;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
+public class MasterClearTest {
+    private MasterClear mMasterClear;
+    @Mock
+    private ScrollView mScrollView;
+    @Mock
+    private LinearLayout mLinearLayout;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mMasterClear = new MasterClear();
+
+        // Make scrollView only have one child
+        when(mScrollView.getChildAt(0)).thenReturn(mLinearLayout);
+        when(mScrollView.getChildCount()).thenReturn(1);
+    }
+
+    @Test
+    public void testHasReachedBottom_NotScrollDown_returnFalse() {
+        initScrollView(100, 0, 200);
+
+        assertThat(mMasterClear.hasReachedBottom(mScrollView)).isFalse();
+    }
+
+    @Test
+    public void testHasReachedBottom_CanNotScroll_returnTrue() {
+        initScrollView(100, 0, 80);
+
+        assertThat(mMasterClear.hasReachedBottom(mScrollView)).isTrue();
+    }
+
+    @Test
+    public void testHasReachedBottom_ScrollToBottom_returnTrue() {
+        initScrollView(100, 100, 200);
+
+        assertThat(mMasterClear.hasReachedBottom(mScrollView)).isTrue();
+    }
+
+    private void initScrollView(int height, int scrollY, int childBottom) {
+        when(mScrollView.getHeight()).thenReturn(height);
+        when(mScrollView.getScrollY()).thenReturn(scrollY);
+        when(mLinearLayout.getBottom()).thenReturn(childBottom);
+    }
+}