Import new C source of truth css-layout

fbshipit-source-id: e866918d6c62fc1cf3a04c269f782b94db9b875a

tests/java/com/facebook/csslayout/CSSNodeTest.java

@@ -0,0 +1,51 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.csslayout;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+/**
+ * Tests for {@link CSSNode}.
+ */
+public class CSSNodeTest {
+
+  @Test
+  public void testAddChildGetParent() {
+    CSSNode parent = new CSSNode();
+    CSSNode child = new CSSNode();
+
+    assertNull(child.getParent());
+    assertEquals(0, parent.getChildCount());
+
+    parent.addChildAt(child, 0);
+
+    assertEquals(1, parent.getChildCount());
+    assertEquals(child, parent.getChildAt(0));
+    assertEquals(parent, child.getParent());
+
+    parent.removeChildAt(0);
+
+    assertNull(child.getParent());
+    assertEquals(0, parent.getChildCount());
+  }
+
+  @Test(expected = IllegalStateException.class)
+  public void testCannotAddChildToMultipleParents() {
+    CSSNode parent1 = new CSSNode();
+    CSSNode parent2 = new CSSNode();
+    CSSNode child = new CSSNode();
+
+    parent1.addChildAt(child, 0);
+    parent2.addChildAt(child, 0);
+  }
+}