Core.Tests: add a failure test for fix suggestion

Author: Mersho

tests/FSharpLint.Core.Tests/Rules/Typography/NoTabCharacters.fs

@@ -27,3 +27,16 @@ type TestTypographyTabCharacterInFile() =
 
         Assert.IsFalse(this.ErrorExistsAt(2, 23))
         Assert.IsFalse(this.ErrorExistsAt(4, 13))
+
+    [<Test>]
+    member this.TabCharacterInFileSuggestedFix() =
+        let source = "\t"
+        let expected = String.replicate 4 " "
+        this.Parse source
+
+        Assert.IsTrue(this.ErrorExistsAt(1, 0))
+
+        let result = this.ApplyQuickFix source
+
+        Assert.AreEqual(expected, result)
+