Added extra unit tests.

Author: dlemstra

tests/Magick.NET.Tests/MagickImageCollectionTests/TheCombineMethod.cs

@@ -20,7 +20,7 @@ public void ShouldThrowExceptionWhenCollectionIsEmpty()
         }
 
         [Fact]
-        public void ShouldCombineSeparatedImages()
+        public void ShouldCombineRgbImage()
         {
             using var rose = new MagickImage(Files.Builtin.Rose);
             using var images = new MagickImageCollection();
@@ -31,6 +31,45 @@ public void ShouldCombineSeparatedImages()
             using var image = images.Combine();
 
             Assert.Equal(rose.TotalColors, image.TotalColors);
+            Assert.Equal(3U, image.ChannelCount);
+            Assert.Equal(0U, image.MetaChannelCount);
+            Assert.False(image.HasAlpha);
+        }
+
+        [Fact]
+        public void ShouldCombineRgbaImage()
+        {
+            using var rose = new MagickImage(Files.MagickNETIconPNG);
+            using var images = new MagickImageCollection();
+            images.AddRange(rose.Separate(Channels.RGBA));
+
+            Assert.Equal(4, images.Count);
+
+            using var image = images.Combine();
+
+            Assert.Equal(rose.TotalColors, image.TotalColors);
+            Assert.Equal(4U, image.ChannelCount);
+            Assert.Equal(0U, image.MetaChannelCount);
+            Assert.True(image.HasAlpha);
+        }
+
+        [Fact]
+        public void ShouldCombineRgbaImageWithMetaChannels()
+        {
+            using var icon = new MagickImage(Files.MagickNETIconPNG);
+            using var images = new MagickImageCollection();
+            images.AddRange(icon.Separate(Channels.RGBA));
+            images.Add(new MagickImage(MagickColors.Black, icon.Width, icon.Height));
+
+            Assert.Equal(5, images.Count);
+
+            using var image = images.Combine();
+
+            Assert.Equal(0.0, icon.Compare(image, ErrorMetric.RootMeanSquared));
+            Assert.Equal(icon.TotalColors, image.TotalColors);
+            Assert.Equal(5U, image.ChannelCount);
+            Assert.Equal(1U, image.MetaChannelCount);
+            Assert.True(image.HasAlpha);
         }
 
         [Fact]
@@ -43,7 +82,49 @@ public void ShouldCombineCmykImage()
             Assert.Equal(4, images.Count);
 
             using var image = images.Combine(ColorSpace.CMYK);
+
             Assert.Equal(0.0, cmyk.Compare(image, ErrorMetric.RootMeanSquared));
+            Assert.Equal(cmyk.TotalColors, image.TotalColors);
+            Assert.Equal(4U, image.ChannelCount);
+            Assert.Equal(0U, image.MetaChannelCount);
+            Assert.False(image.HasAlpha);
+        }
+
+        [Fact]
+        public void ShouldCombineCmykaImage()
+        {
+            using var cmyk = new MagickImage(Files.CMYKJPG);
+            using var images = new MagickImageCollection();
+            images.AddRange(cmyk.Separate(Channels.CMYKA));
+            images.Add(new MagickImage(MagickColors.Black, cmyk.Width, cmyk.Height));
+
+            Assert.Equal(5, images.Count);
+
+            using var image = images.Combine(ColorSpace.CMYK);
+
+            Assert.Equal(cmyk.TotalColors, image.TotalColors);
+            Assert.Equal(5U, image.ChannelCount);
+            Assert.Equal(0U, image.MetaChannelCount);
+            Assert.True(image.HasAlpha);
+        }
+
+        [Fact]
+        public void ShouldCombineCmykaImageWithMetaChannels()
+        {
+            using var cmyk = new MagickImage(Files.CMYKJPG);
+            using var images = new MagickImageCollection();
+            images.AddRange(cmyk.Separate(Channels.CMYKA));
+            images.Add(new MagickImage(MagickColors.Black, cmyk.Width, cmyk.Height));
+            images.Add(new MagickImage(MagickColors.Purple, cmyk.Width, cmyk.Height));
+
+            Assert.Equal(6, images.Count);
+
+            using var image = images.Combine(ColorSpace.CMYK);
+
+            Assert.Equal(cmyk.TotalColors, image.TotalColors);
+            Assert.Equal(6U, image.ChannelCount);
+            Assert.Equal(1U, image.MetaChannelCount);
+            Assert.True(image.HasAlpha);
         }
     }
 }