diff --git a/NightLight.Core.Tests/MutationCaseAttribute.fs b/NightLight.Core.Tests/MutationCaseAttribute.fs
new file mode 100644
index 0000000..12e6475
--- /dev/null
+++ b/NightLight.Core.Tests/MutationCaseAttribute.fs
@@ -0,0 +1,13 @@
+namespace Mutannot
+
+open System
+
+[<AttributeUsage(AttributeTargets.Method, AllowMultiple = true)>]
+type MutationCaseAttribute(id: string, file: string, line: int, find: string, replace: string) =
+    inherit Attribute()
+
+    member _.Id = id
+    member _.File = file
+    member _.Line = line
+    member _.Find = find
+    member _.Replace = replace
diff --git a/NightLight.Core.Tests/NightLight.Core.Tests.fsproj b/NightLight.Core.Tests/NightLight.Core.Tests.fsproj
index 8c14702..4364d43 100644
--- a/NightLight.Core.Tests/NightLight.Core.Tests.fsproj
+++ b/NightLight.Core.Tests/NightLight.Core.Tests.fsproj
@@ -7,6 +7,7 @@
     </PropertyGroup>
 
     <ItemGroup>
+        <Compile Include="MutationCaseAttribute.fs" />
         <Compile Include="FakeHome.fs" />
         <Compile Include="GenHelpers.fs" />
         <Compile Include="InteractionListHelpers.fs" />
diff --git a/flake.lock b/flake.lock
index 181aa01..52a4b9b 100644
--- a/flake.lock
+++ b/flake.lock
@@ -42,6 +42,27 @@
         "url": "https://codeberg.org/svenvanheugten/git-check-assertions.git"
       }
     },
+    "mutannot": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1777439386,
+        "narHash": "sha256-nTBcu7NsN1jwoXr8SoKaW+0EPb5klTU6SSWuXOeuEuA=",
+        "ref": "main",
+        "rev": "1019d3c5d04d441d12b915876110f7493270b988",
+        "revCount": 19,
+        "type": "git",
+        "url": "https://git.memcmp.org/svenvanheugten/mutannot.git"
+      },
+      "original": {
+        "ref": "main",
+        "type": "git",
+        "url": "https://git.memcmp.org/svenvanheugten/mutannot.git"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1773507054,
@@ -62,6 +83,7 @@
       "inputs": {
         "flake-utils": "flake-utils",
         "git-check-assertions": "git-check-assertions",
+        "mutannot": "mutannot",
         "nixpkgs": "nixpkgs"
       }
     },
diff --git a/flake.nix b/flake.nix
index 5447ef1..074d9ba 100644
--- a/flake.nix
+++ b/flake.nix
@@ -7,6 +7,10 @@
       inputs.nixpkgs.follows = "nixpkgs";
       inputs.flake-utils.follows = "flake-utils";
     };
+    mutannot = {
+      url = "git+https://git.memcmp.org/svenvanheugten/mutannot.git?ref=main";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
   outputs =
     {
@@ -14,6 +18,7 @@
       nixpkgs,
       flake-utils,
       git-check-assertions,
+      mutannot,
     }:
     flake-utils.lib.eachDefaultSystem (
       system:
@@ -26,6 +31,7 @@
           packages = [
             pkgs.dotnet-sdk_10
             git-check-assertions.packages.${system}.default
+            mutannot.packages.${system}.default
           ];
         };
       }