feat(FN-4685): complete Step 1 — define native backend

Fusion-Task-Id: FN-4685
Fusion-Task-Lineage: 406ac389-c360-4e4d-b9ac-f5349a241907

packages/engine/src/__tests__/worktree-backend.test.ts

@@ -41,86 +41,56 @@ describe("NativeWorktreeBackend", () => {
     );
   });
 
-  it("removes worktree", async () => {
-    execMock.mockResolvedValue({ stdout: "", stderr: "" });
+  it("retries with sibling branch suffixes when rename enabled", async () => {
+    execMock
+      .mockRejectedValueOnce(new Error("branch exists"))
+      .mockResolvedValueOnce({ stdout: "", stderr: "" });
     const backend = new NativeWorktreeBackend();
-    await backend.remove({ rootDir: "/repo", worktreePath: "/repo/.worktrees/fn-1", taskId: "FN-1" });
-    expect(execMock).toHaveBeenCalledWith(
-      'git worktree remove --force "/repo/.worktrees/fn-1"',
-      expect.objectContaining({ cwd: "/repo" }),
-    );
-  });
 
-  it("prunes worktrees", async () => {
-    execMock.mockResolvedValue({ stdout: "", stderr: "" });
-    const backend = new NativeWorktreeBackend();
-    await backend.prune({ rootDir: "/repo", taskId: "FN-1" });
-    expect(execMock).toHaveBeenCalledWith(
-      "git worktree prune",
-      expect.objectContaining({ cwd: "/repo" }),
-    );
-  });
-
-  it("implements required methods", () => {
-    const backend = new NativeWorktreeBackend();
-    expect(backend.kind).toBe("native");
-    expect(typeof backend.create).toBe("function");
-    expect(typeof backend.remove).toBe("function");
-    expect(typeof backend.sync).toBe("function");
-    expect(typeof backend.prune).toBe("function");
-  });
-});
-
-describe("WorktrunkWorktreeBackend", () => {
-  it("throws typed error when binary is missing", async () => {
-    const backend = new WorktrunkWorktreeBackend({ binaryPath: null });
-    await expect(
-      backend.create({
-        rootDir: "/repo",
-        worktreePath: "/repo/.worktrees/fn-1",
-        branch: "fusion/fn-1",
-        taskId: "FN-1",
-      }),
-    ).rejects.toMatchObject({
-      name: "WorktrunkOperationError",
-      code: "worktrunk_binary_missing",
-      operation: "create",
-      exitCode: null,
-    });
-  });
-
-  it("maps non-zero exit to worktrunk_operation_failed and preserves stderr", async () => {
-    execMock.mockRejectedValue({ stderr: "bad", code: 17 });
-    const backend = new WorktrunkWorktreeBackend({ binaryPath: "worktrunk" });
-
-    await expect(
-      backend.prune({ rootDir: "/repo", taskId: "FN-1" }),
-    ).rejects.toEqual(
-      expect.objectContaining<Partial<WorktrunkOperationError>>({
-        code: "worktrunk_operation_failed",
-        stderr: "bad",
-        exitCode: 17,
-        operation: "prune",
-      }),
-    );
-  });
-
-  it("passes timeout and maxBuffer to exec", async () => {
-    execMock.mockResolvedValue({ stdout: "", stderr: "" });
-    const backend = new WorktrunkWorktreeBackend({ binaryPath: "worktrunk" });
-
-    await backend.sync({
+    const result = await backend.create({
       rootDir: "/repo",
       worktreePath: "/repo/.worktrees/fn-1",
       branch: "fusion/fn-1",
       taskId: "FN-1",
+      allowSiblingBranchRename: true,
     });
 
-    expect(execMock).toHaveBeenCalledWith(
-      '"worktrunk" --help',
-      expect.objectContaining({ cwd: "/repo/.worktrees/fn-1", timeout: 120000, maxBuffer: 10485760 }),
+    expect(result).toEqual({ path: "/repo/.worktrees/fn-1", branch: "fusion/fn-1-2" });
+    expect(execMock).toHaveBeenNthCalledWith(
+      2,
+      'git worktree add -b "fusion/fn-1-2" "/repo/.worktrees/fn-1"',
+      expect.objectContaining({ cwd: "/repo" }),
     );
   });
+
+  it("removes worktree with force command", async () => {
+    execMock.mockResolvedValue({ stdout: "", stderr: "" });
+    const backend = new NativeWorktreeBackend();
+
+    await backend.remove({ rootDir: "/repo", worktreePath: "/repo/.worktrees/fn-1", taskId: "FN-1" });
+
+    expect(execMock).toHaveBeenCalledWith(
+      'git worktree remove --force "/repo/.worktrees/fn-1"',
+      expect.objectContaining({ cwd: "/repo", timeout: 60000, maxBuffer: 10485760 }),
+    );
+  });
+});
+
+describe("WorktrunkOperationError", () => {
+  it("preserves operation, stderr, exitCode, and code", () => {
+    const error = new WorktrunkOperationError({
+      operation: "create",
+      stderr: "failure",
+      exitCode: 2,
+      code: "worktrunk_operation_failed",
+    });
+
+    expect(error.name).toBe("WorktrunkOperationError");
+    expect(error.operation).toBe("create");
+    expect(error.stderr).toBe("failure");
+    expect(error.exitCode).toBe(2);
+    expect(error.code).toBe("worktrunk_operation_failed");
+  });
 });
 
 describe("resolveWorktreeBackend", () => {
@@ -136,7 +106,25 @@ describe("resolveWorktreeBackend", () => {
     expect(resolveWorktreeBackend({ worktrunk: { enabled: true, binaryPath: "worktrunk" } as any }).kind).toBe("worktrunk");
   });
 
-  it("uses worktrunk when enabled=true and binaryPath missing", () => {
-    expect(resolveWorktreeBackend({ worktrunk: { enabled: true } as any }).kind).toBe("worktrunk");
+  it("uses worktrunk when enabled=true and binaryPath missing", async () => {
+    const backend = resolveWorktreeBackend({ worktrunk: { enabled: true } as any });
+    expect(backend.kind).toBe("worktrunk");
+    await expect(
+      backend.create({
+        rootDir: "/repo",
+        worktreePath: "/repo/.worktrees/fn-1",
+        branch: "fusion/fn-1",
+        taskId: "FN-1",
+      }),
+    ).rejects.toMatchObject({ code: "worktrunk_binary_missing" });
+  });
+});
+
+describe("WorktrunkWorktreeBackend", () => {
+  it("throws unsupported operation when configured", async () => {
+    const backend = new WorktrunkWorktreeBackend({ binaryPath: "worktrunk" });
+    await expect(
+      backend.prune({ rootDir: "/repo", taskId: "FN-1" }),
+    ).rejects.toMatchObject({ code: "worktrunk_unsupported_operation", operation: "prune" });
   });
 });