diff --git a/image/color/color_test.go b/image/color/color_test.go
index f61fc02..98804fc 100644
--- a/image/color/color_test.go
+++ b/image/color/color_test.go
@@ -1,6 +1,23 @@
 package ucolor
 
 import "testing"
+import "image/color"
+
+func TestTransparent (test *testing.T) {
+	if Transparent(color.NRGBA { A: 255 }) {
+		test.Fatal("false positive")
+	}
+	if !Transparent(color.NRGBA { A: 0 }) {
+		test.Fatal("false negative")
+	}
+}
+
+func TestToRGBA (test *testing.T) {
+	rgba := ToRGBA(color.NRGBA { R: 123, G: 100, B: 23, A: 230 })
+	if rgba != (color.RGBA { R: 111, G: 90, B: 20, A: 230 }) {
+		test.Fatalf("wrong value: %v", rgba)
+	}
+}
 
 func TestPremultiply (test *testing.T) {
 	r, g, b, a := Premultiply(0xFFFF, 0xFFFF, 0xFFFF, 0x8888)