Add test cases for Grayscale jpeg

tests/ImageSharp.Tests/Formats/Jpg/JpegEncoderTests.cs

@@ -80,13 +80,18 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
         [WithSolidFilledImages(nameof(BitsPerPixel_Quality), 1, 1, 255, 100, 50, 255, PixelTypes.Rgba32)]
         [WithTestPatternImages(nameof(BitsPerPixel_Quality), 7, 5, PixelTypes.Rgba32)]
         [WithTestPatternImages(nameof(BitsPerPixel_Quality), 600, 400, PixelTypes.Rgba32)]
+        [WithSolidFilledImages(nameof(BitsPerPixel_Quality), 1, 1, 100, 100, 100, 255, PixelTypes.L8)]
         public void EncodeBaseline_WorksWithDifferentSizes<TPixel>(TestImageProvider<TPixel> provider, JpegSubsample subsample, int quality)
             where TPixel : unmanaged, IPixel<TPixel> => TestJpegEncoderCore(provider, subsample, quality);
 
         [Theory]
         [WithFile(TestImages.Png.BikeGrayscale, nameof(BitsPerPixel_Quality), PixelTypes.L8)]
+        [WithSolidFilledImages(nameof(BitsPerPixel_Quality), 1, 1, 100, 100, 100, 255, PixelTypes.Rgba32)]
         [WithSolidFilledImages(nameof(BitsPerPixel_Quality), 1, 1, 100, 100, 100, 255, PixelTypes.L8)]
-        public void EncodeBaseline_GrayscaleWorksWithDifferentSizes<TPixel>(TestImageProvider<TPixel> provider, JpegSubsample subsample, int quality)
+        [WithSolidFilledImages(nameof(BitsPerPixel_Quality), 1, 1, 100, 100, 100, 255, PixelTypes.L16)]
+        [WithSolidFilledImages(nameof(BitsPerPixel_Quality), 1, 1, 100, 100, 100, 255, PixelTypes.La16)]
+        [WithSolidFilledImages(nameof(BitsPerPixel_Quality), 1, 1, 100, 100, 100, 255, PixelTypes.La32)]
+        public void EncodeBaseline_Grayscale<TPixel>(TestImageProvider<TPixel> provider, JpegSubsample subsample, int quality)
             where TPixel : unmanaged, IPixel<TPixel> => TestJpegEncoderCore(provider, subsample, quality, JpegColorType.Luminance);
 
         [Theory]