perf: automate vitest thread candidate scans

test/scripts/test-find-thread-candidates.test.ts

@@ -0,0 +1,116 @@
+import { describe, expect, it } from "vitest";
+import {
+  getExistingThreadCandidateExclusions,
+  parseArgs,
+  selectThreadCandidateFiles,
+  summarizeThreadBenchmark,
+} from "../../scripts/test-find-thread-candidates.mjs";
+
+describe("scripts/test-find-thread-candidates parseArgs", () => {
+  it("parses explicit thresholds and positional files", () => {
+    expect(
+      parseArgs([
+        "--limit",
+        "4",
+        "--min-duration-ms",
+        "600",
+        "--min-gain-ms",
+        "120",
+        "--min-gain-pct",
+        "15",
+        "--json",
+        "src/a.test.ts",
+      ]),
+    ).toEqual({
+      config: "vitest.unit.config.ts",
+      limit: 4,
+      minDurationMs: 600,
+      minGainMs: 120,
+      minGainPct: 15,
+      json: true,
+      files: ["src/a.test.ts"],
+    });
+  });
+});
+
+describe("scripts/test-find-thread-candidates exclusions", () => {
+  it("collects already-pinned files across behavior buckets", () => {
+    expect(
+      getExistingThreadCandidateExclusions({
+        unit: {
+          isolated: [{ file: "src/a.test.ts" }],
+          singletonIsolated: [{ file: "src/b.test.ts" }],
+          threadSingleton: [{ file: "src/c.test.ts" }],
+          vmForkSingleton: [{ file: "src/d.test.ts" }],
+        },
+      }),
+    ).toEqual(new Set(["src/a.test.ts", "src/b.test.ts", "src/c.test.ts", "src/d.test.ts"]));
+  });
+});
+
+describe("scripts/test-find-thread-candidates selection", () => {
+  it("keeps only known, unpinned files above the duration floor", () => {
+    expect(
+      selectThreadCandidateFiles({
+        files: ["src/a.test.ts", "src/b.test.ts", "src/c.test.ts", "src/d.test.ts"],
+        timings: {
+          files: {
+            "src/a.test.ts": { durationMs: 1100 },
+            "src/b.test.ts": { durationMs: 700 },
+            "src/c.test.ts": { durationMs: 300 },
+          },
+        },
+        exclude: new Set(["src/b.test.ts"]),
+        limit: 10,
+        minDurationMs: 500,
+      }),
+    ).toEqual(["src/a.test.ts"]);
+  });
+
+  it("allows explicit unknown-duration files when requested", () => {
+    expect(
+      selectThreadCandidateFiles({
+        files: ["src/a.test.ts", "src/b.test.ts"],
+        timings: {
+          files: {
+            "src/a.test.ts": { durationMs: 700 },
+          },
+        },
+        exclude: new Set(),
+        limit: 10,
+        minDurationMs: 500,
+        includeUnknownDuration: true,
+      }),
+    ).toEqual(["src/a.test.ts", "src/b.test.ts"]);
+  });
+});
+
+describe("scripts/test-find-thread-candidates summarizeThreadBenchmark", () => {
+  it("recommends clear thread wins", () => {
+    expect(
+      summarizeThreadBenchmark({
+        file: "src/a.test.ts",
+        forks: { exitCode: 0, elapsedMs: 1000, stderr: "", stdout: "" },
+        threads: { exitCode: 0, elapsedMs: 780, stderr: "", stdout: "" },
+        minGainMs: 100,
+        minGainPct: 10,
+      }),
+    ).toMatchObject({
+      file: "src/a.test.ts",
+      gainMs: 220,
+      recommended: true,
+    });
+  });
+
+  it("rejects thread failures even when the measured wall time is lower", () => {
+    expect(
+      summarizeThreadBenchmark({
+        file: "src/b.test.ts",
+        forks: { exitCode: 0, elapsedMs: 1000, stderr: "", stdout: "" },
+        threads: { exitCode: 1, elapsedMs: 400, stderr: "TypeError", stdout: "" },
+        minGainMs: 100,
+        minGainPct: 10,
+      }).recommended,
+    ).toBe(false);
+  });
+});