fix(ci): select mutation fixtures when suites change

bin/smoke/mutation-reproof.smoke.ts

@@ -90,6 +90,7 @@ function makeRepo(mutate: (root: string) => void): { root: string; base: string;
       "",
     ].join("\n"));
     writeFileSync(join(root, "smoke", "mutations", `${name}.mutations.json`), JSON.stringify({
+      suite: `${name}.suite.mjs`,
       command: `node ${name}.suite.mjs`,
       mutations: [{
         name: `the ${name} cap is removed`,
@@ -228,7 +229,45 @@ try {
     );
   }
 
-  // 5. A selected fixture whose suite is ALREADY RED before any mutation. a.mjs changes (so a's
+  // 5. A suite-only change must select the fixture that names that suite, even though neither its
+  //    config nor guarded source changed. The other suite is the negative arm: changing a file whose
+  //    name merely looks like a suite must not select either fixture.
+  {
+    const { root, base, head } = build((r) => {
+      writeFileSync(join(r, "a.suite.mjs"), [
+        "// suite-only change; a.mjs and the fixture config are untouched",
+        "import { capped_a } from './a.mjs';",
+        "if (capped_a(100) !== 32) { console.error('✗ FAIL: the a cap holds'); process.exit(1); }",
+        "console.log('✓ the a cap holds');",
+        "",
+      ].join("\n"));
+      git(r, ["add", "a.suite.mjs"]);
+      git(r, ["commit", "--quiet", "-m", "change only a's suite"]);
+    });
+    const { status, out } = scan(root, base, head);
+    check(
+      "a suite-only change selects exactly the fixture that names that suite",
+      status === 0
+        && eq(selectedPaths(out), ["smoke/mutations/a.mutations.json"])
+        && JSON.stringify(okCounts(out)) === JSON.stringify({ discriminated: 1, preRed: 0, inconclusive: 0 }),
+      `status=${status} selected=${JSON.stringify(selectedPaths(out))} counts=${JSON.stringify(okCounts(out))}\n${out}`,
+    );
+  }
+  {
+    const { root, base, head } = build((r) => {
+      writeFileSync(join(r, "unrelated.suite.mjs"), "// not named by any fixture\n");
+      git(r, ["add", "unrelated.suite.mjs"]);
+      git(r, ["commit", "--quiet", "-m", "change an unrelated suite"]);
+    });
+    const { status, out } = scan(root, base, head);
+    check(
+      "an unrelated suite selects no fixture",
+      status === 0 && selectedPaths(out).length === 0,
+      `status=${status} selected=${JSON.stringify(selectedPaths(out))}\n${out}`,
+    );
+  }
+
+  // 6. A selected fixture whose suite is ALREADY RED before any mutation. a.mjs changes (so a's
   //    fixture is selected) but a's suite fails unconditionally, so mutation-proof refuses at its
   //    baseline (exit 4). That is the suite's own defect, not this diff's — the #1279/sandbox-guard
   //    shape the reviewer reproduced. The gate must report it as PRE-RED, name exactly that fixture,
@@ -263,7 +302,7 @@ try {
     );
   }
 
-  // 6. INCONCLUSIVE (not a timeout — deterministic): a mutation that leaves the suite exiting 0 but
+  // 7. INCONCLUSIVE (not a timeout — deterministic): a mutation that leaves the suite exiting 0 but
   //    never printing its named assertion. mutation-proof grades that INCONCLUSIVE, "a green status
   //    is not a pass". The gate must report it as INCONCLUSIVE, not fail, and NOT collapse it into
   //    SURVIVED (false blocker) or KILLED (false clearance). This is the outcome the reviewer flagged
@@ -303,7 +342,7 @@ try {
     );
   }
 
-  // 7. A real all-clear that reaches the OK summary (a fixture whose mutant is genuinely killed).
+  // 8. A real all-clear that reaches the OK summary (a fixture whose mutant is genuinely killed).
   //    Its counts must read `discriminated > 0, pre-red 0, inconclusive 0` — the positive contrast to
   //    cases 5 and 6, so "the gate worked and everything was clean" is not the same output as "every
   //    selected fixture was pre-red or inconclusive".

bin/smoke/mutations/mutation-reproof.json

@@ -1,6 +1,6 @@
 {
   "suite": "bin/smoke/mutation-reproof.smoke.ts",
-  "guard": "changed guarded source re-proves its fixture; a deleted or renamed-away source is a loud dangling failure naming the exact fixture; both sides of a rename enter the changed set",
+  "guard": "changed fixture config, suite, or guarded source re-proves its fixture; a deleted or renamed-away source is a loud dangling failure naming the exact fixture; both sides of a rename enter the changed set",
   "command": "pnpm smoke:mutation-reproof",
   "grades": "tool",
   "proveWith": "pnpm mutation-proof --config bin/smoke/mutations/mutation-reproof.json",
@@ -21,6 +21,14 @@
       "expectRed": "the gate FAILS on a renamed-away guarded source and names exactly the dangling fixture",
       "cell": "the gate FAILS on a renamed-away guarded source and names exactly the dangling fixture"
     },
+    {
+      "name": "a changed configured suite is ignored by changed-set selection",
+      "file": "scripts/mutation-reproof.mjs",
+      "find": "  || (typeof suite === \"string\" && changed.has(suite))\n",
+      "replace": "",
+      "expectRed": "a suite-only change selects exactly the fixture that names that suite",
+      "cell": "a suite-only change selects exactly the fixture that names that suite"
+    },
     {
       "name": "a dangling fixture is no longer refused, so a deleted source stops being a loud failure",
       "file": "scripts/mutation-reproof.mjs",

scripts/mutation-reproof.mjs

@@ -81,7 +81,7 @@ function loadCorpus(root, paths) {
       errors.push(`${path}: no top-level "mutations" array`);
       continue;
     }
-    fixtures.push({ path, mutations: config.mutations });
+    fixtures.push({ path, suite: config.suite, mutations: config.mutations });
   }
   return { fixtures, errors };
 }
@@ -158,7 +158,8 @@ if (errors.length) {
 
 const { changed, diffSize } = a.all ? { changed: new Set(), diffSize: 0 } : changedSet(root, a.base, head);
 
-let selected = fixtures.filter(({ path, mutations }) => a.all || changed.has(path)
+let selected = fixtures.filter(({ path, suite, mutations }) => a.all || changed.has(path)
+  || (typeof suite === "string" && changed.has(suite))
   || mutations.some((mutation) => typeof mutation?.file === "string" && changed.has(mutation.file)));
 if (shard) selected = selected.filter(({ path }) => shardOf(path, Number(shard[2])) === Number(shard[1]));
 
@@ -186,7 +187,7 @@ console.log(`mutation reproof: ${selected.length} fixture(s) selected from ${fix
     ? " for a full sweep"
     : ` (diff ${diffSize} record(s), ${changed.size} changed path(s), corpus ${fixtures.length})`));
 if (selected.length === 0) {
-  console.log("No mutation fixtures to re-prove: no fixture config or guarded source intersects the diff.");
+  console.log("No mutation fixtures to re-prove: no fixture config, suite, or guarded source intersects the diff.");
   process.exit(0);
 }
 console.log(`selected fixture paths:\n${selected.map(({ path }) => `  ${path}`).join("\n")}`);