feat(FN-4343): complete Step 2 — dual-signal frontend ux auto-skip

Fusion-Task-Id: FN-4343
Fusion-Task-Lineage: b880b71a-9250-4d9e-bdac-8298a73058f7

packages/engine/src/__tests__/executor-workflow-step-scope.test.ts

@@ -0,0 +1,104 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import "./executor-test-helpers.js";
+import { TaskExecutor } from "../executor.js";
+import { createMockStore, mockedExecSync, resetExecutorMocks } from "./executor-test-helpers.js";
+
+function createTask() {
+  return {
+    id: "FN-001",
+    title: "Test",
+    description: "Test task",
+    column: "in-progress" as const,
+    dependencies: [],
+    steps: [{ name: "Preflight", status: "done" as const }],
+    currentStep: 0,
+    log: [],
+    enabledWorkflowSteps: ["frontend-ux-design"],
+    createdAt: new Date().toISOString(),
+    updatedAt: new Date().toISOString(),
+  };
+}
+
+function createFrontendStep() {
+  return {
+    id: "frontend-ux-design",
+    name: "Frontend UX Design",
+    description: "UI review",
+    prompt: "Review UI",
+    enabled: true,
+    createdAt: new Date().toISOString(),
+    updatedAt: new Date().toISOString(),
+  };
+}
+
+function mockDiffFiles(files: string[]) {
+  mockedExecSync.mockImplementation((cmd: string | string[]) => {
+    if (typeof cmd === "string" && cmd.includes("git merge-base HEAD origin/main")) {
+      return Buffer.from("abc123\n");
+    }
+    if (typeof cmd === "string" && cmd.includes("git diff --name-only abc123..HEAD")) {
+      return Buffer.from(files.join("\n"));
+    }
+    return Buffer.from("");
+  });
+}
+
+describe("executor workflow step scope gating", () => {
+  beforeEach(() => {
+    resetExecutorMocks();
+  });
+
+  it.each([
+    {
+      name: "both signals empty",
+      diffFiles: [] as string[],
+      declaredFiles: [] as string[],
+      expectedSkip: false,
+    },
+    {
+      name: "diff only non-frontend",
+      diffFiles: ["packages/engine/src/executor.ts"],
+      declaredFiles: [],
+      expectedSkip: true,
+    },
+    {
+      name: "declared only non-frontend",
+      diffFiles: [],
+      declaredFiles: [".github/workflows/ci.yml"],
+      expectedSkip: true,
+      expectedLog: "declared File Scope contains no frontend/UI files",
+    },
+    {
+      name: "both present and both non-frontend",
+      diffFiles: ["packages/engine/src/executor.ts"],
+      declaredFiles: [".github/workflows/ci.yml"],
+      expectedSkip: true,
+      expectedLog: "declared File Scope contains no frontend/UI files",
+    },
+  ])("FN-4343 auto-skip matrix: $name", async ({ diffFiles, declaredFiles, expectedSkip, expectedLog }) => {
+    const store = createMockStore();
+    const task = createTask();
+    store.getTask.mockResolvedValue(task as any);
+    store.getWorkflowStep.mockResolvedValue(createFrontendStep() as any);
+    store.parseFileScopeFromPrompt.mockResolvedValue(declaredFiles);
+    mockDiffFiles(diffFiles);
+
+    const executor = new TaskExecutor(store as any, "/tmp/test", {} as any);
+    const executeStepSpy = vi.spyOn(executor as any, "executeWorkflowStep").mockResolvedValue({ success: true, output: "ok" });
+
+    const result = await (executor as any).runWorkflowSteps(task as any, "/tmp/test", {} as any);
+
+    expect(result).toEqual({ allPassed: true });
+    if (expectedSkip) {
+      expect(executeStepSpy).not.toHaveBeenCalled();
+      const statuses = store.updateTask.mock.calls.flatMap((call: any[]) => call[1]?.workflowStepResults ?? []).map((r: any) => r.status);
+      expect(statuses).toContain("skipped");
+      if (expectedLog) {
+        const logged = store.logEntry.mock.calls.map((call: any[]) => String(call[1] ?? ""));
+        expect(logged.some((line: string) => line.includes(expectedLog))).toBe(true);
+      }
+    } else {
+      expect(executeStepSpy).toHaveBeenCalledTimes(1);
+    }
+  });
+});