diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/BlankProvider.cs b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/BlankProvider.cs
index 78821aac1..7821d0b51 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/BlankProvider.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/BlankProvider.cs
@@ -19,13 +19,14 @@ namespace SixLabors.ImageSharp.Tests
                 this.Width = width;
                 this.Height = height;
             }
+
             public BlankProvider()
             {
                 this.Width = 100;
                 this.Height = 100;
             }
 
-            public override string SourceFileOrDescription => $"Blank{this.Width}x{this.Height}";
+            public override string SourceFileOrDescription => TestUtils.AsInvariantString($"Blank{this.Width}x{this.Height}");
 
             protected int Height { get; private set; }
 
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/SolidProvider.cs b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/SolidProvider.cs
index df5b424a2..70e762585 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/SolidProvider.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/SolidProvider.cs
@@ -47,7 +47,7 @@ namespace SixLabors.ImageSharp.Tests
             }
 
             public override string SourceFileOrDescription
-                => $"Solid{this.Width}x{this.Height}_({this.r},{this.g},{this.b},{this.a})";
+                => TestUtils.AsInvariantString($"Solid{this.Width}x{this.Height}_({this.r},{this.g},{this.b},{this.a})");
 
             public override Image<TPixel> GetImage()
             {
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestPatternProvider.cs b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestPatternProvider.cs
index 0b25991ff..f04f891f8 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestPatternProvider.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestPatternProvider.cs
@@ -30,7 +30,7 @@ namespace SixLabors.ImageSharp.Tests
             {
             }
 
-            public override string SourceFileOrDescription => $"TestPattern{this.Width}x{this.Height}";
+            public override string SourceFileOrDescription => TestUtils.AsInvariantString($"TestPattern{this.Width}x{this.Height}");
 
             public override Image<TPixel> GetImage()
             {
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs b/tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs
index 340fc600a..02f8ddd7e 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs
@@ -95,8 +95,6 @@ namespace SixLabors.ImageSharp.Tests
             return $"{this.GetTestOutputDir()}/{this.TestName}{pixName}{fn}{details}{extension}";
         }
 
-        private static string Inv(FormattableString formattable) => System.FormattableString.Invariant(formattable);
-
         /// <summary>
         /// Gets the recommended file name for the output of the test
         /// </summary>
@@ -123,7 +121,7 @@ namespace SixLabors.ImageSharp.Tests
                 TypeInfo info = type.GetTypeInfo();
                 if (info.IsPrimitive || info.IsEnum || type == typeof(decimal))
                 {
-                    detailsString = Inv($"{testOutputDetails}");
+                    detailsString = TestUtils.AsInvariantString($"{testOutputDetails}");
                 }
                 else
                 {
@@ -132,7 +130,7 @@ namespace SixLabors.ImageSharp.Tests
                     detailsString = string.Join(
                         "_",
                         properties.ToDictionary(x => x.Name, x => x.GetValue(testOutputDetails))
-                            .Select(x => Inv($"{x.Key}-{x.Value}"))
+                            .Select(x => TestUtils.AsInvariantString($"{x.Key}-{x.Value}"))
                         );
                 }
             }
diff --git a/tests/ImageSharp.Tests/TestUtilities/TestUtils.cs b/tests/ImageSharp.Tests/TestUtilities/TestUtils.cs
index 85729acd3..f71793ff2 100644
--- a/tests/ImageSharp.Tests/TestUtilities/TestUtils.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/TestUtils.cs
@@ -101,7 +101,7 @@ namespace SixLabors.ImageSharp.Tests
 
         public static string ToCsv<T>(this IEnumerable<T> items, string separator = ",")
         {
-            return string.Join(separator, items.Select(o => string.Format(CultureInfo.InvariantCulture, "{0}", o)));
+            return String.Join(separator, items.Select(o => String.Format(CultureInfo.InvariantCulture, "{0}", o)));
         }
 
         public static Type GetClrType(this PixelTypes pixelType) => PixelTypes2ClrTypes[pixelType];
@@ -227,5 +227,7 @@ namespace SixLabors.ImageSharp.Tests
                 image.DebugSave(provider, testOutputDetails);
             }
         }
+
+        public static string AsInvariantString(this FormattableString formattable) => System.FormattableString.Invariant(formattable);
     }
 }
\ No newline at end of file