diff --git a/services/tests/servicestests/src/com/android/server/wm/TaskStackContainersTests.java b/services/tests/servicestests/src/com/android/server/wm/TaskStackContainersTests.java
new file mode 100644
index 0000000..7463102
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/wm/TaskStackContainersTests.java
@@ -0,0 +1,69 @@
+/*
+ * 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.server.wm;
+
+import static android.app.ActivityManager.StackId.PINNED_STACK_ID;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import android.platform.test.annotations.Presubmit;
+import android.support.test.filters.SmallTest;
+import android.support.test.runner.AndroidJUnit4;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Tests for the {@link DisplayContent.TaskStackContainers} container in {@link DisplayContent}.
+ *
+ * Build/Install/Run:
+ *  bit FrameworksServicesTests:com.android.server.wm.TaskStackContainersTests
+ */
+@SmallTest
+@Presubmit
+@RunWith(AndroidJUnit4.class)
+public class TaskStackContainersTests extends WindowTestsBase {
+
+    @Test
+    public void testStackPositionChildAt() throws Exception {
+        // Test that always-on-top stack can't be moved to position other than top.
+        final TaskStack stack1 = createTaskStackOnDisplay(sDisplayContent);
+        final TaskStack stack2 = createTaskStackOnDisplay(sDisplayContent);
+        sDisplayContent.addStackToDisplay(PINNED_STACK_ID, true);
+        final TaskStack pinnedStack = sWm.mStackIdToStack.get(PINNED_STACK_ID);
+
+        final WindowContainer taskStackContainer = stack1.getParent();
+
+        final int stack1Pos = taskStackContainer.mChildren.indexOf(stack1);
+        final int stack2Pos = taskStackContainer.mChildren.indexOf(stack2);
+        final int pinnedStackPos = taskStackContainer.mChildren.indexOf(pinnedStack);
+
+        taskStackContainer.positionChildAt(WindowContainer.POSITION_BOTTOM, pinnedStack, false);
+        assertEquals(taskStackContainer.mChildren.get(stack1Pos), stack1);
+        assertEquals(taskStackContainer.mChildren.get(stack2Pos), stack2);
+        assertEquals(taskStackContainer.mChildren.get(pinnedStackPos), pinnedStack);
+
+        taskStackContainer.positionChildAt(1, pinnedStack, false);
+        assertEquals(taskStackContainer.mChildren.get(stack1Pos), stack1);
+        assertEquals(taskStackContainer.mChildren.get(stack2Pos), stack2);
+        assertEquals(taskStackContainer.mChildren.get(pinnedStackPos), pinnedStack);
+    }
+}