coverage: add test for isreadonly on missing fileinfo (#233)

Based on TestableIO/System.IO.Abstractions#942
add a test for correct behaviour of `FileInfo.IsReadOnly` when the file
does not exist.

---------

Co-authored-by: Valentin Breuß <[email protected]>

Author: vbreuss

Tests/Testably.Abstractions.Tests/FileSystem/FileInfo/Tests.cs

@@ -85,6 +85,15 @@ public void Extension_WithTrailingDot_ShouldReturnExpectedValue()
 		}
 	}
 
+	[SkippableTheory]
+	[AutoData]
+	public void IsReadOnly_MissingFile_ShouldBeTrue(string path)
+	{
+		IFileInfo fileInfo = FileSystem.FileInfo.New(path);
+
+		fileInfo.IsReadOnly.Should().BeTrue();
+	}
+
 	[SkippableTheory]
 	[AutoData]
 	public void IsReadOnly_SetToFalse_ShouldRemoveReadOnlyAttribute(string path)