diff --git a/resize_test.go b/resize_test.go
index 4fcc091..cb8dfe3 100644
--- a/resize_test.go
+++ b/resize_test.go
@@ -20,10 +20,7 @@ func TestResize(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
-	err = Write("fixtures/test_out.jpg", newImg)
-	if err != nil {
-		t.Fatal("Cannot save the image")
-	}
+	Write("fixtures/test_out.jpg", newImg)
 }
 
 func TestRotate(t *testing.T) {
@@ -39,10 +36,7 @@ func TestRotate(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
-	err = Write("fixtures/test_rotate_out.jpg", newImg)
-	if err != nil {
-		t.Fatal("Cannot save the image")
-	}
+	Write("fixtures/test_rotate_out.jpg", newImg)
 }
 
 func TestCorruptedImage(t *testing.T) {
@@ -58,10 +52,7 @@ func TestCorruptedImage(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
-	err = Write("fixtures/test_corrupt_out.jpg", newImg)
-	if err != nil {
-		t.Fatal("Cannot save the image")
-	}
+	Write("fixtures/test_corrupt_out.jpg", newImg)
 }
 
 func TestInvalidRotate(t *testing.T) {
@@ -77,10 +68,7 @@ func TestInvalidRotate(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
-	err = Write("fixtures/test_invalid_rotate_out.jpg", newImg)
-	if err != nil {
-		t.Fatal("Cannot save the image")
-	}
+	Write("fixtures/test_invalid_rotate_out.jpg", newImg)
 }
 
 func TestConvert(t *testing.T) {
@@ -112,10 +100,7 @@ func TestConvert(t *testing.T) {
 		t.Fatal("Invalid image size")
 	}
 
-	err = Write("fixtures/test_out.png", newImg)
-	if err != nil {
-		t.Fatal("Cannot save the image")
-	}
+	Write("fixtures/test_out.png", newImg)
 }
 
 func TestResizePngWithTransparency(t *testing.T) {
@@ -147,10 +132,7 @@ func TestResizePngWithTransparency(t *testing.T) {
 		t.Fatal("Invalid image size")
 	}
 
-	err = Write("fixtures/transparent_out.png", newImg)
-	if err != nil {
-		t.Fatal("Cannot save the image")
-	}
+	Write("fixtures/transparent_out.png", newImg)
 }
 
 func runBenchmarkResize(file string, o Options, b *testing.B) {
diff --git a/vips.h b/vips.h
index 2537cae..23b9613 100644
--- a/vips.h
+++ b/vips.h
@@ -243,3 +243,4 @@ vips_watermark(VipsImage *in, VipsImage **out, watermarkTextOptions *to, waterma
 	g_object_unref(base);
 	return 0;
 };
+
diff --git a/vips_test.go b/vips_test.go
index 533e810..5eab2c3 100644
--- a/vips_test.go
+++ b/vips_test.go
@@ -18,37 +18,102 @@ func TestVipsRead(t *testing.T) {
 	}
 
 	for _, file := range files {
-		img, _ := os.Open(path.Join("fixtures", file.name))
-		buf, _ := ioutil.ReadAll(img)
-		defer img.Close()
-
-		image, imageType, _ := vipsRead(buf)
+		image, imageType, _ := vipsRead(readImage(file.name))
 		if image == nil {
 			t.Fatal("Empty image")
 		}
 		if imageType != file.expected {
-			t.Fatal("Empty image")
+			t.Fatal("Invalid image type")
 		}
 	}
 }
 
 func TestVipsSave(t *testing.T) {
-	img, _ := os.Open(path.Join("fixtures", "test.jpg"))
-	buf, _ := ioutil.ReadAll(img)
-	defer img.Close()
+	image, _, _ := vipsRead(readImage("test.jpg"))
+	options := vipsSaveOptions{Quality: 95, Type: JPEG}
 
-	image, _, _ := vipsRead(buf)
-	if image == nil {
+	buf, err := vipsSave(image, options)
+	if err != nil {
+		t.Fatal("Cannot save the image")
+	}
+	if len(buf) == 0 {
 		t.Fatal("Empty image")
 	}
+}
 
-	options := vipsSaveOptions{Quality: 95, Type: JPEG}
+func TestVipsRotate(t *testing.T) {
+	image, _, _ := vipsRead(readImage("test.jpg"))
 
-	buf, err := vipsSave(image, options)
+	newImg, err := vipsRotate(image, D90)
+	if err != nil {
+		t.Fatal("Cannot save the image")
+	}
+
+	buf, _ := vipsSave(newImg, vipsSaveOptions{Quality: 95})
+	if len(buf) == 0 {
+		t.Fatal("Empty image")
+	}
+}
+
+func TestVipsZoom(t *testing.T) {
+	image, _, _ := vipsRead(readImage("test.jpg"))
+
+	newImg, err := vipsRotate(image, D90)
 	if err != nil {
 		t.Fatal("Cannot save the image")
 	}
+
+	buf, _ := vipsSave(newImg, vipsSaveOptions{Quality: 95})
 	if len(buf) == 0 {
 		t.Fatal("Empty image")
 	}
 }
+
+func TestVipsWatermark(t *testing.T) {
+	image, _, _ := vipsRead(readImage("test.jpg"))
+
+	watermark := Watermark{
+		Text:       "Copy me if you can",
+		Font:       "sans bold 12",
+		Opacity:    0.5,
+		Width:      200,
+		DPI:        100,
+		Margin:     100,
+		Background: Color{255, 255, 255},
+	}
+
+	newImg, err := vipsWatermark(image, watermark)
+	if err != nil {
+		t.Errorf("Cannot add watermark: %s", err)
+	}
+
+	buf, _ := vipsSave(newImg, vipsSaveOptions{Quality: 95})
+	if len(buf) == 0 {
+		t.Fatal("Empty image")
+	}
+}
+
+func TestVipsImageType(t *testing.T) {
+	imgType := vipsImageType(readImage("test.jpg"))
+	if imgType != JPEG {
+		t.Fatal("Invalid image type")
+	}
+}
+
+func TestVipsMemory(t *testing.T) {
+	mem := VipsMemory()
+
+	if mem.Memory < 1024 {
+		t.Fatal("Invalid memory")
+	}
+	if mem.Allocations == 0 {
+		t.Fatal("Invalid memory allocations")
+	}
+}
+
+func readImage(file string) []byte {
+	img, _ := os.Open(path.Join("fixtures", file))
+	buf, _ := ioutil.ReadAll(img)
+	defer img.Close()
+	return buf
+}