From 7ec7447808725f761dc7cba83fea676c4420158f Mon Sep 17 00:00:00 2001
From: Anton Firszov <antonfir@gmail.com>
Date: Thu, 25 Nov 2021 20:29:29 +0100
Subject: [PATCH] fix DetectEncoder tests

---
 tests/ImageSharp.Tests/Image/ImageTests.cs | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/tests/ImageSharp.Tests/Image/ImageTests.cs b/tests/ImageSharp.Tests/Image/ImageTests.cs
index 2015f8e388..0a9e2817a5 100644
--- a/tests/ImageSharp.Tests/Image/ImageTests.cs
+++ b/tests/ImageSharp.Tests/Image/ImageTests.cs
@@ -339,11 +339,22 @@ namespace SixLabors.ImageSharp.Tests
             }
 
             [Fact]
-            public void UnknownExtension_ReturnsNull()
+            public void UnknownExtension_ThrowsNotSupportedException()
             {
                 using var image = new Image<L8>(1, 1);
-                IImageEncoder encoder = image.DetectEncoder("dummy.yolo");
-                Assert.Null(encoder);
+                Assert.Throws<NotSupportedException>(() => image.DetectEncoder("dummy.yolo"));
+            }
+
+            [Fact]
+            public void NoDetectorRegisteredForKnownExtension_ThrowsNotSupportedException()
+            {
+                var configuration = new Configuration();
+                var format = new TestFormat();
+                configuration.ImageFormatsManager.AddImageFormat(format);
+                configuration.ImageFormatsManager.AddImageFormatDetector(new MockImageFormatDetector(format));
+
+                using var image = new Image<L8>(configuration, 1, 1);
+                Assert.Throws<NotSupportedException>(() => image.DetectEncoder($"dummy.{format.Extension}"));
             }
         }
     }