Alpha to trns tests

tests/reduction.rs

@@ -130,6 +130,30 @@ fn rgba_8_should_be_rgb_8() {
     );
 }
 
+#[test]
+fn rgba_16_should_be_rgb_trns_16() {
+    test_it_converts(
+        "tests/files/rgba_16_should_be_rgb_trns_16.png",
+        true,
+        ColorType::RGBA,
+        BitDepth::Sixteen,
+        ColorType::RGB,
+        BitDepth::Sixteen,
+    );
+}
+
+#[test]
+fn rgba_8_should_be_rgb_trns_8() {
+    test_it_converts(
+        "tests/files/rgba_8_should_be_rgb_trns_8.png",
+        true,
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::RGB,
+        BitDepth::Eight,
+    );
+}
+
 #[test]
 fn rgba_16_should_be_palette_8() {
     test_it_converts(
@@ -694,6 +718,30 @@ fn grayscale_8_should_be_grayscale_8() {
     );
 }
 
+#[test]
+fn grayscale_alpha_16_should_be_grayscale_trns_16() {
+    test_it_converts(
+        "tests/files/grayscale_alpha_16_should_be_grayscale_trns_16.png",
+        true,
+        ColorType::GrayscaleAlpha,
+        BitDepth::Sixteen,
+        ColorType::Grayscale,
+        BitDepth::Sixteen,
+    );
+}
+
+#[test]
+fn grayscale_alpha_8_should_be_grayscale_trns_8() {
+    test_it_converts(
+        "tests/files/grayscale_alpha_8_should_be_grayscale_trns_8.png",
+        true,
+        ColorType::GrayscaleAlpha,
+        BitDepth::Eight,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+    );
+}
+
 #[test]
 fn small_files() {
     let input = PathBuf::from("tests/files/small_files.png");