perf(mutation): stop booting a Postgres container for every mutant

stryker.config.json

@@ -13,16 +13,26 @@
     "@stryker-mutator/typescript-checker"
   ],
   "testRunner": "vitest",
-  "checkers": ["typescript"],
+  "checkers": [
+    "typescript"
+  ],
   "tsconfigFile": "tsconfig.json",
   "coverageAnalysis": "perTest",
   "thresholds": {
     "high": 80,
     "low": 60,
     "break": 60
   },
-  "reporters": ["html", "clear-text", "progress"],
+  "reporters": [
+    "html",
+    "clear-text",
+    "progress"
+  ],
   "htmlReporter": {
     "fileName": "reports/mutation/mutation.html"
-  }
+  },
+  "vitest": {
+    "configFile": "vitest.stryker.config.ts"
+  },
+  "ignoreStatic": true
 }

vitest.stryker.config.ts

@@ -0,0 +1,37 @@
+import { defineConfig } from "vitest/config";
+
+// Vitest config used ONLY by Stryker (wired via stryker.config.json's
+// `vitest.configFile`). It deliberately omits the `globalSetup` that starts a
+// Postgres testcontainer.
+//
+// Why: Stryker runs vitest once per mutant batch across `concurrency` workers
+// (default: CPU cores - 1). globalSetup fires on every one of those, so a
+// Postgres container was being booted and fully migrated to run unit tests that
+// take milliseconds — measured at 8.92s of setup for 29ms of tests, and 18
+// concurrent containers observed on the runner.
+//
+// Consequence: tests that need a database can't run here, so the DB-backed
+// files below are excluded along with tests/ (integration). Mutants covered
+// only by those report as NoCoverage rather than Survived, which is honest
+// signal about unit-test strength instead of a container tax.
+export default defineConfig({
+  resolve: {
+    tsconfigPaths: true,
+  },
+  test: {
+    globals: true,
+    environment: "node",
+    include: ["src/**/*.test.ts"],
+    exclude: [
+      "node_modules/**",
+      "e2e/**",
+      // Need a live Postgres via tests/global-setup.ts.
+      "src/lib/demo-mode.test.ts",
+      "src/lib/simplefin/queries.test.ts",
+      "src/lib/plaid/queries.test.ts",
+      "src/lib/jobs/backfill-balances.test.ts",
+      "src/lib/jobs/backfill-transfers.test.ts",
+    ],
+    testTimeout: 30_000,
+  },
+});