From 3f6e3ad8dc13ddb0aa244178321788ddaee209dc Mon Sep 17 00:00:00 2001
From: Myoxocephalus <cj.adolfsson@gmail.com>
Date: Fri, 18 Oct 2024 12:21:16 +0200
Subject: [PATCH] feat: Add string mutators for LastIndexOf and IndexOf.
 (#3054)

Added string mutators.
---
 docs/mutations.md                                             | 2 ++
 .../Mutators/StringMethodMutatorTests.cs                      | 2 ++
 src/Stryker.Core/Stryker.Core/Mutators/StringMethodMutator.cs | 4 +++-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/docs/mutations.md b/docs/mutations.md
index 16ab045dd..4fe129a1b 100644
--- a/docs/mutations.md
+++ b/docs/mutations.md
@@ -173,6 +173,8 @@ Do you have a suggestion for a (new) mutator? Feel free to create an [issue](htt
 | `ElementAt()`          | `'\0'`               |
 | `ElementAtOrDefault()` | `'\0'`               |
 | `EndsWith()`           | `StartsWith()`       |
+| `IndexOf()`            | `LastIndexOf()`      |
+| `LastIndexOf()`        | `IndexOf()`          |
 | `PadLeft()`            | `PadRight()`         |
 | `PadRight()`           | `PadLeft()`          |
 | `StartsWith()`         | `EndsWith()`         |
diff --git a/src/Stryker.Core/Stryker.Core.UnitTest/Mutators/StringMethodMutatorTests.cs b/src/Stryker.Core/Stryker.Core.UnitTest/Mutators/StringMethodMutatorTests.cs
index 477182126..9739cc82a 100644
--- a/src/Stryker.Core/Stryker.Core.UnitTest/Mutators/StringMethodMutatorTests.cs
+++ b/src/Stryker.Core/Stryker.Core.UnitTest/Mutators/StringMethodMutatorTests.cs
@@ -59,6 +59,8 @@ void TestMethod() {
         "String Method Mutation (Replace ToLowerInvariant() with ToUpperInvariant())")]
     [DataRow("testString.PadLeft(10)", "PadRight", "String Method Mutation (Replace PadLeft() with PadRight())")]
     [DataRow("testString.PadRight(10)", "PadLeft", "String Method Mutation (Replace PadRight() with PadLeft())")]
+    [DataRow("testString.LastIndexOf(c)", "IndexOf", "String Method Mutation (Replace LastIndexOf() with IndexOf())")]
+    [DataRow("testString.IndexOf(c)", "LastIndexOf", "String Method Mutation (Replace IndexOf() with LastIndexOf())")]
     public void ShouldMutateStringMethods(string expression, string mutatedMethod, string expectedDisplayName)
     {
         var (semanticModel, expressionSyntax) = CreateSemanticModelFromExpression(expression);
diff --git a/src/Stryker.Core/Stryker.Core/Mutators/StringMethodMutator.cs b/src/Stryker.Core/Stryker.Core/Mutators/StringMethodMutator.cs
index 815866082..99367a780 100644
--- a/src/Stryker.Core/Stryker.Core/Mutators/StringMethodMutator.cs
+++ b/src/Stryker.Core/Stryker.Core/Mutators/StringMethodMutator.cs
@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
@@ -63,6 +63,8 @@ private static string GetReplacement(string identifier) =>
             "ToLowerInvariant" => "ToUpperInvariant",
             "PadLeft" => "PadRight",
             "PadRight" => "PadLeft",
+            "IndexOf" => "LastIndexOf",
+            "LastIndexOf" => "IndexOf",
             _ => null
         };