chore(quality-gate): enforce mutation testing on quality gate

.github/workflows/mutation.yml

@@ -0,0 +1,50 @@
+name: Mutation
+
+# Separate from build-and-test on purpose: release.yml waits only on build-and-test, so
+# this never delays a release. It runs in parallel with build-and-test on the PR; making
+# it block a merge is a branch-protection choice (mark the `mutation` check required).
+#
+# `dotnet stryker --since:origin/master` mutates only the changed diff (hermetic — E2E is
+# filtered out in each stryker-config.json), then gate.sh --mutation fails on any new
+# survivor. Only changed packages are mutated, so an unchanged package costs nothing.
+
+on:
+  pull_request:
+    branches: [master]
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  mutation:
+    runs-on: ubuntu-latest
+    # Ceiling, not the norm: Stryker.NET mutates everything if a non-C# file changed
+    # (stryker-net#3013), so the timeout bounds that worst case.
+    timeout-minutes: 30
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0   # --since and the gate's diff both need origin/master
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          global-json-file: global.json
+
+      - name: Install Stryker
+        run: dotnet tool install --global dotnet-stryker
+
+      - name: Mutate changed packages
+        run: |
+          git diff --name-only origin/master...HEAD -- 'packages/**/*.cs' \
+            | sed -E 's#(packages/[^/]+)/.*#\1#' | sort -u \
+            | while read -r pkg; do
+                cfg=$(ls "$pkg"/*.Tests/stryker-config.json 2>/dev/null) || continue
+                ( cd "$(dirname "$cfg")" && dotnet stryker --since:origin/master )
+              done
+
+      - name: Evaluate mutation reports
+        run: ./scripts/quality-gate/gate.sh packages --mutation

packages/Core/Core.Tests/stryker-config.json

@@ -8,6 +8,7 @@
     "reporters": [
       "json",
       "progress"
-    ]
+    ],
+    "test-case-filter": "TestCategory!=E2E"
   }
 }

packages/Functions/Functions.Tests/stryker-config.json

@@ -8,6 +8,7 @@
     "reporters": [
       "json",
       "progress"
-    ]
+    ],
+    "test-case-filter": "TestCategory!=E2E"
   }
 }

packages/Gotrue/Gotrue.Tests/stryker-config.json

@@ -8,6 +8,7 @@
     "reporters": [
       "json",
       "progress"
-    ]
+    ],
+    "test-case-filter": "TestCategory!=E2E"
   }
 }

packages/Postgrest/Postgrest.Tests/stryker-config.json

@@ -8,6 +8,7 @@
     "reporters": [
       "json",
       "progress"
-    ]
+    ],
+    "test-case-filter": "TestCategory!=E2E"
   }
 }

packages/Realtime/Realtime.Tests/stryker-config.json

@@ -8,6 +8,7 @@
     "reporters": [
       "json",
       "progress"
-    ]
+    ],
+    "test-case-filter": "TestCategory!=E2E"
   }
 }

packages/Storage/Storage.Tests/stryker-config.json

@@ -8,6 +8,7 @@
     "reporters": [
       "json",
       "progress"
-    ]
+    ],
+    "test-case-filter": "TestCategory!=E2E"
   }
 }

packages/Supabase/Supabase.Tests/stryker-config.json

@@ -8,6 +8,7 @@
     "reporters": [
       "json",
       "progress"
-    ]
+    ],
+    "test-case-filter": "TestCategory!=E2E"
   }
 }

scripts/quality-gate/fixtures/_base/Sample.Tests/stryker-config.json

@@ -0,0 +1,7 @@
+{
+  "stryker-config": {
+    "project": "Sample.csproj",
+    "test-projects": ["Sample.Tests.csproj"],
+    "test-case-filter": "TestCategory!=E2E"
+  }
+}

scripts/quality-gate/fixtures/mutation-clean/expect.json

@@ -0,0 +1,9 @@
+{
+  "description": "Every mutant in the changed file is killed — the tests actually assert on the new code. The mutation stage PASSes.",
+  "mode": "--mutation",
+  "exit": 0,
+  "verdict": "PASS",
+  "stages": [
+    { "id": "3", "status": "PASS" }
+  ]
+}

scripts/quality-gate/fixtures/mutation-clean/overlay/Sample/Calculator.cs

@@ -0,0 +1,6 @@
+namespace Sample;
+
+public class Calculator
+{
+    public int Add(int a, int b) => a + b;
+}

scripts/quality-gate/fixtures/mutation-clean/overlay/StrykerOutput/reports/mutation-report.json

@@ -0,0 +1,47 @@
+{
+  "schemaVersion": "2",
+  "thresholds": {
+    "high": 80,
+    "low": 60
+  },
+  "files": {
+    "/repo/packages/Sample/Calculator.cs": {
+      "language": "cs",
+      "source": "namespace Sample;\n\npublic class Calculator\n{\n    public int Add(int a, int b) => a + b;\n}\n",
+      "mutants": [
+        {
+          "id": "1",
+          "mutatorName": "Arithmetic",
+          "replacement": "a - b",
+          "location": {
+            "start": {
+              "line": 5,
+              "column": 41
+            },
+            "end": {
+              "line": 5,
+              "column": 46
+            }
+          },
+          "status": "Killed"
+        },
+        {
+          "id": "2",
+          "mutatorName": "Arithmetic",
+          "replacement": "a * b",
+          "location": {
+            "start": {
+              "line": 5,
+              "column": 41
+            },
+            "end": {
+              "line": 5,
+              "column": 46
+            }
+          },
+          "status": "Killed"
+        }
+      ]
+    }
+  }
+}

scripts/quality-gate/fixtures/mutation-no-report/expect.json

@@ -0,0 +1,9 @@
+{
+  "description": "The diff changed a file but no Stryker report exists — 'couldn't check' must never read as 'no survivors'. The stage SKIPs and the run is INCOMPLETE (exit 2).",
+  "mode": "--mutation",
+  "exit": 2,
+  "verdict": "INCOMPLETE",
+  "stages": [
+    { "id": "3", "status": "SKIP", "detailContains": "no usable mutation report" }
+  ]
+}

scripts/quality-gate/fixtures/mutation-no-report/overlay/Sample/Calculator.cs

@@ -0,0 +1,6 @@
+namespace Sample;
+
+public class Calculator
+{
+    public int Add(int a, int b) => a + b;
+}

scripts/quality-gate/fixtures/mutation-old-survivor/expect.json

@@ -0,0 +1,9 @@
+{
+  "description": "A survivor exists, but in Legacy.cs — a file this diff never touched. It's pre-existing debt, not this change's regression, so it's ignored; the changed file's mutants are all killed, so the stage PASSes.",
+  "mode": "--mutation",
+  "exit": 0,
+  "verdict": "PASS",
+  "stages": [
+    { "id": "3", "status": "PASS" }
+  ]
+}

scripts/quality-gate/fixtures/mutation-old-survivor/overlay/Sample/Calculator.cs

@@ -0,0 +1,6 @@
+namespace Sample;
+
+public class Calculator
+{
+    public int Add(int a, int b) => a + b;
+}

scripts/quality-gate/fixtures/mutation-old-survivor/overlay/StrykerOutput/reports/mutation-report.json

@@ -0,0 +1,53 @@
+{
+  "schemaVersion": "2",
+  "thresholds": {
+    "high": 80,
+    "low": 60
+  },
+  "files": {
+    "/repo/packages/Sample/Calculator.cs": {
+      "language": "cs",
+      "source": "namespace Sample;\n\npublic class Calculator\n{\n    public int Add(int a, int b) => a + b;\n}\n",
+      "mutants": [
+        {
+          "id": "1",
+          "mutatorName": "Arithmetic",
+          "replacement": "a - b",
+          "location": {
+            "start": {
+              "line": 5,
+              "column": 41
+            },
+            "end": {
+              "line": 5,
+              "column": 46
+            }
+          },
+          "status": "Killed"
+        }
+      ]
+    },
+    "/repo/packages/Sample/Legacy.cs": {
+      "language": "cs",
+      "source": "namespace Sample;\n\npublic class Legacy\n{\n    public int Twice(int n) => n * 2;\n}\n",
+      "mutants": [
+        {
+          "id": "2",
+          "mutatorName": "Arithmetic",
+          "replacement": "n / 2",
+          "location": {
+            "start": {
+              "line": 5,
+              "column": 32
+            },
+            "end": {
+              "line": 5,
+              "column": 37
+            }
+          },
+          "status": "Survived"
+        }
+      ]
+    }
+  }
+}

scripts/quality-gate/fixtures/mutation-survivor/expect.json

@@ -0,0 +1,9 @@
+{
+  "description": "A surviving mutant lands on a line this diff added — a test executes the new code but asserts nothing, so line coverage is happy and the mutant lives. Only the mutation stage must FAIL.",
+  "mode": "--mutation",
+  "exit": 1,
+  "verdict": "FAIL",
+  "stages": [
+    { "id": "3", "status": "FAIL", "detailContains": "new survivor" }
+  ]
+}

scripts/quality-gate/fixtures/mutation-survivor/overlay/Sample/Calculator.cs

@@ -0,0 +1,6 @@
+namespace Sample;
+
+public class Calculator
+{
+    public int Add(int a, int b) => a + b;
+}

scripts/quality-gate/fixtures/mutation-survivor/overlay/StrykerOutput/reports/mutation-report.json

@@ -0,0 +1,47 @@
+{
+  "schemaVersion": "2",
+  "thresholds": {
+    "high": 80,
+    "low": 60
+  },
+  "files": {
+    "/repo/packages/Sample/Calculator.cs": {
+      "language": "cs",
+      "source": "namespace Sample;\n\npublic class Calculator\n{\n    public int Add(int a, int b) => a + b;\n}\n",
+      "mutants": [
+        {
+          "id": "1",
+          "mutatorName": "Arithmetic",
+          "replacement": "a - b",
+          "location": {
+            "start": {
+              "line": 5,
+              "column": 41
+            },
+            "end": {
+              "line": 5,
+              "column": 46
+            }
+          },
+          "status": "Survived"
+        },
+        {
+          "id": "2",
+          "mutatorName": "Arithmetic",
+          "replacement": "a * b",
+          "location": {
+            "start": {
+              "line": 5,
+              "column": 41
+            },
+            "end": {
+              "line": 5,
+              "column": 46
+            }
+          },
+          "status": "Killed"
+        }
+      ]
+    }
+  }
+}