diff --git a/image/color/color_test.go b/image/color/color_test.go
new file mode 100644
index 0000000..f61fc02
--- /dev/null
+++ b/image/color/color_test.go
@@ -0,0 +1,17 @@
+package ucolor
+
+import "testing"
+
+func TestPremultiply (test *testing.T) {
+	r, g, b, a := Premultiply(0xFFFF, 0xFFFF, 0xFFFF, 0x8888)
+	if r != 0x8888 || g != 0x8888 || b != 0x8888 || a != 0x8888 {
+		test.Fatalf("wrong value: %08x %08x %08x %08x", r, g, b, a)
+	}
+}
+
+func TestUnpremultiply (test *testing.T) {
+	r, g, b, a := Unpremultiply(0x8888, 0x8888, 0x8888, 0x8888)
+	if r != 0xFFFF || g != 0xFFFF || b != 0xFFFF || a != 0x8888 {
+		test.Fatalf("wrong value: %08x %08x %08x %08x", r, g, b, a)
+	}
+}