test: add typed failure classification module (#333)

scripts/test-failure-reasons.cjs

@@ -0,0 +1,34 @@
+'use strict';
+
+const TEST_GATE_REASON = Object.freeze({
+  PASS: 'pass',
+  TEST_FAILURE: 'test_failure',
+  INFRA_FAILURE: 'infra_failure',
+  UNKNOWN_FAILURE: 'unknown_failure',
+});
+
+/**
+ * Classify gsd-test style output + exit code into a typed reason.
+ * @param {{exitCode:number, output?:string}} input
+ * @returns {{ok:boolean, reason:string}}
+ */
+function classifyTestGateResult(input) {
+  const exitCode = Number(input?.exitCode ?? 0);
+  const output = String(input?.output ?? '');
+
+  if (exitCode === 0) return { ok: true, reason: TEST_GATE_REASON.PASS };
+
+  // gsd-test/gsd-test-summary infrastructure class (exit 2)
+  if (exitCode === 2 || /infrastructure failure|worktree\.Construct/i.test(output)) {
+    return { ok: false, reason: TEST_GATE_REASON.INFRA_FAILURE };
+  }
+
+  // test failures (non-zero plus explicit FAIL lines)
+  if (/\bFAIL\b|\d+\s+failures?\)|failed\)/i.test(output)) {
+    return { ok: false, reason: TEST_GATE_REASON.TEST_FAILURE };
+  }
+
+  return { ok: false, reason: TEST_GATE_REASON.UNKNOWN_FAILURE };
+}
+
+module.exports = { TEST_GATE_REASON, classifyTestGateResult };