diff --git a/libs/ui/tests/Android.bp b/libs/ui/tests/Android.bp
index 665469e..373fa4f 100644
--- a/libs/ui/tests/Android.bp
+++ b/libs/ui/tests/Android.bp
@@ -71,3 +71,10 @@
     ],
     cflags: ["-Wall", "-Werror"],
 }
+
+cc_test {
+    name: "Size_test",
+    shared_libs: ["libui"],
+    srcs: ["Size_test.cpp"],
+    cflags: ["-Wall", "-Werror"],
+}
diff --git a/libs/ui/tests/Size_test.cpp b/libs/ui/tests/Size_test.cpp
new file mode 100644
index 0000000..69e1ac8
--- /dev/null
+++ b/libs/ui/tests/Size_test.cpp
@@ -0,0 +1,184 @@
+/*
+ * Copyright 2019 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.
+ */
+
+#define LOG_TAG "SizeTest"
+
+#include <cmath>
+#include <cstdlib>
+
+#include <ui/Size.h>
+
+#include <gtest/gtest.h>
+
+namespace android {
+namespace ui {
+
+TEST(SizeTest, BasicConstructionAndEqualityComparison) {
+    Size s(123, 456);
+
+    EXPECT_EQ(123, s.width);
+    EXPECT_EQ(123, s.getWidth());
+
+    EXPECT_EQ(456, s.height);
+    EXPECT_EQ(456, s.getHeight());
+
+    EXPECT_EQ(Size(123, 456), s);
+    EXPECT_NE(Size(456, 123), s);
+}
+
+TEST(SizeTest, BasicLessThanComparison) {
+    EXPECT_TRUE(Size(0, 1) < Size(2, 3));
+    EXPECT_FALSE(Size(2, 3) < Size(0, 1));
+
+    EXPECT_TRUE(Size(0, 3) < Size(2, 1));
+    EXPECT_FALSE(Size(2, 1) < Size(0, 3));
+
+    EXPECT_TRUE(Size(0, 1) < Size(0, 3));
+    EXPECT_FALSE(Size(0, 3) < Size(0, 1));
+
+    EXPECT_FALSE(Size(1, 1) < Size(1, 1));
+}
+
+TEST(SizeTest, ValidAndEmpty) {
+    {
+        Size s;
+        EXPECT_FALSE(s.isValid());
+        EXPECT_FALSE(s.isEmpty());
+    }
+
+    {
+        Size s(-1, -1);
+        EXPECT_FALSE(s.isValid());
+        EXPECT_FALSE(s.isEmpty());
+    }
+
+    {
+        Size s(1, -1000);
+        EXPECT_FALSE(s.isValid());
+        EXPECT_FALSE(s.isEmpty());
+    }
+
+    {
+        Size s(-1000, 1);
+        EXPECT_FALSE(s.isValid());
+        EXPECT_FALSE(s.isEmpty());
+    }
+
+    {
+        Size s(-1000, -1000);
+        EXPECT_FALSE(s.isValid());
+        EXPECT_FALSE(s.isEmpty());
+    }
+
+    {
+        const auto& s = Size::INVALID;
+        EXPECT_FALSE(s.isValid());
+        EXPECT_FALSE(s.isEmpty());
+    }
+
+    {
+        Size s(123, 456);
+        s.makeInvalid();
+        EXPECT_FALSE(s.isValid());
+        EXPECT_FALSE(s.isEmpty());
+    }
+
+    {
+        Size s(0, 0);
+        EXPECT_TRUE(s.isValid());
+        EXPECT_TRUE(s.isEmpty());
+    }
+
+    {
+        const auto& s = Size::EMPTY;
+        EXPECT_TRUE(s.isValid());
+        EXPECT_TRUE(s.isEmpty());
+    }
+
+    {
+        Size s(123, 456);
+        s.clear();
+        EXPECT_TRUE(s.isValid());
+        EXPECT_TRUE(s.isEmpty());
+    }
+
+    {
+        Size s(123, 456);
+        EXPECT_TRUE(s.isValid());
+        EXPECT_FALSE(s.isEmpty());
+    }
+}
+
+TEST(SizeTest, Set) {
+    {
+        Size s;
+        s.setWidth(0);
+        EXPECT_EQ(Size(0, -1), s);
+    }
+
+    {
+        Size s;
+        s.setHeight(0);
+        EXPECT_EQ(Size(-1, 0), s);
+    }
+
+    {
+        Size s;
+        s.set(123, 456);
+        EXPECT_EQ(Size(123, 456), s);
+    }
+}
+
+template <typename T, typename U>
+void ClampTest(T input, U expected) {
+    // The constructor, set(), setWidth() and setHeight() all allow arbitrary
+    // conversions from other numeric types, and implement clamping if necessary.
+
+    EXPECT_EQ(Size(expected, expected), Size(input, input));
+
+    {
+        Size s;
+        s.set(input, input);
+        EXPECT_EQ(Size(expected, expected), s);
+    }
+
+    {
+        Size s;
+        s.setWidth(input);
+        EXPECT_EQ(expected, s.width);
+    }
+
+    {
+        Size s;
+        s.setHeight(input);
+        EXPECT_EQ(expected, s.height);
+    }
+}
+
+TEST(SizeTest, Int8RangeIsNotClamped) {
+    ClampTest(std::numeric_limits<int8_t>::max(), std::numeric_limits<int8_t>::max());
+    ClampTest(int8_t(0), int8_t(0));
+    ClampTest(std::numeric_limits<int8_t>::lowest(), std::numeric_limits<int8_t>::lowest());
+}
+
+TEST(SizeTest, FloatRangeIsClamped) {
+    ClampTest(std::numeric_limits<float>::max(), std::numeric_limits<int32_t>::max());
+    ClampTest(float(0), int32_t(0));
+    ClampTest(std::numeric_limits<float>::lowest(), std::numeric_limits<int32_t>::lowest());
+}
+
+} // namespace ui
+} // namespace android