fix: use mock.module for image-downloader tests

Replace the _fsForTest/DI patterns with Bun's native mock.module() API.
This mocks fs/promises at the module loader level, which works reliably
on Linux where jest.fn() call tracking fails cross-module. The source
code is now clean with no testing artifacts.

Also switches from jest.fn() to mock() (Bun's native API) for Octokit
mocks in these tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test/image-downloader.test.ts

@@ -5,13 +5,26 @@ import {
   spyOn,
   beforeEach,
   afterEach,
-  jest,
+  mock,
   setSystemTime,
 } from "bun:test";
+
+// Mock fs/promises at the module loader level. Bun hoists mock.module calls
+// before imports, so the source module's `import fs from "fs/promises"` gets
+// these mocks. This avoids cross-module jest.fn() tracking bugs on Linux Bun.
+const mockMkdir = mock(() => Promise.resolve(undefined as any));
+const mockWriteFile = mock(() => Promise.resolve(undefined as any));
+
+mock.module("fs/promises", () => ({
+  default: {
+    mkdir: mockMkdir,
+    writeFile: mockWriteFile,
+  },
+}));
+
 import {
   downloadCommentImages,
   type CommentWithImages,
-  type FsOps,
 } from "../src/github/utils/image-downloader";
 import type { Octokits } from "../src/github/api/client";
 
@@ -22,14 +35,6 @@ describe("downloadCommentImages", () => {
   let fetchSpy: any;
   let savedServerUrl: string | undefined;
 
-  // Mock functions for fs operations — injected via parameter, no module mutation needed
-  const mockMkdir = jest.fn().mockResolvedValue(undefined);
-  const mockWriteFile = jest.fn().mockResolvedValue(undefined);
-  const mockFsOps: FsOps = {
-    mkdir: mockMkdir as any,
-    writeFile: mockWriteFile as any,
-  };
-
   beforeEach(() => {
     // Pin GITHUB_SERVER_URL so tests pass regardless of runner environment.
     // The image-downloader reads process.env directly at call time.
@@ -67,13 +72,13 @@ describe("downloadCommentImages", () => {
     return {
       rest: {
         issues: {
-          getComment: jest.fn(),
-          get: jest.fn(),
+          getComment: mock(() => {}),
+          get: mock(() => {}),
         },
         pulls: {
-          getReviewComment: jest.fn(),
-          getReview: jest.fn(),
-          get: jest.fn(),
+          getReviewComment: mock(() => {}),
+          getReview: mock(() => {}),
+          get: mock(() => {}),
         },
       },
     } as any as Octokits;
@@ -83,13 +88,7 @@ describe("downloadCommentImages", () => {
     const mockOctokit = createMockOctokit();
     const comments: CommentWithImages[] = [];
 
-    await downloadCommentImages(
-      mockOctokit,
-      "owner",
-      "repo",
-      comments,
-      mockFsOps,
-    );
+    await downloadCommentImages(mockOctokit, "owner", "repo", comments);
 
     expect(mockMkdir).toHaveBeenCalledWith("/tmp/github-images", {
       recursive: true,
@@ -111,7 +110,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(result.size).toBe(0);
@@ -129,11 +127,13 @@ describe("downloadCommentImages", () => {
 
     // Mock octokit response
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     // Mock fetch for image download
     const mockArrayBuffer = new ArrayBuffer(8);
@@ -155,7 +155,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(mockOctokit.rest.issues.getComment).toHaveBeenCalledWith({
@@ -192,11 +191,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/review.jpg?jwt=token";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.pulls.getReviewComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.pulls.getReviewComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -216,7 +217,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(mockOctokit.rest.pulls.getReviewComment).toHaveBeenCalledWith({
@@ -239,11 +239,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/body.png?jwt=token";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.pulls.getReview = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.pulls.getReview = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -264,7 +266,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(mockOctokit.rest.pulls.getReview).toHaveBeenCalledWith({
@@ -288,11 +289,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/issue.gif?jwt=token";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.get = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.issues.get = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -312,7 +315,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(mockOctokit.rest.issues.get).toHaveBeenCalledWith({
@@ -337,11 +339,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/pr.webp?jwt=token";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.pulls.get = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.pulls.get = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -361,7 +365,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(mockOctokit.rest.pulls.get).toHaveBeenCalledWith({
@@ -389,11 +392,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/2.jpg?jwt=token2";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl1}"><img src="${signedUrl2}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl1}"><img src="${signedUrl2}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -413,7 +418,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(fetchSpy).toHaveBeenCalledTimes(2);
@@ -436,11 +440,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/dup.png?jwt=token";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -465,7 +471,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(fetchSpy).toHaveBeenCalledTimes(1); // Only downloaded once
@@ -480,11 +485,13 @@ describe("downloadCommentImages", () => {
     const imageUrl = "https://github.com/user-attachments/assets/missing.png";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: null,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: null,
+        },
+      }),
+    );
 
     const comments: CommentWithImages[] = [
       {
@@ -499,7 +506,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(result.size).toBe(0);
@@ -515,11 +521,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/error.png?jwt=token";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: false,
@@ -540,7 +548,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(result.size).toBe(0);
@@ -555,9 +562,9 @@ describe("downloadCommentImages", () => {
     const imageUrl = "https://github.com/user-attachments/assets/api-error.png";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest
-      .fn()
-      .mockRejectedValue(new Error("API rate limit exceeded"));
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.reject(new Error("API rate limit exceeded")),
+    );
 
     const comments: CommentWithImages[] = [
       {
@@ -572,7 +579,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(result.size).toBe(0);
@@ -618,11 +624,13 @@ describe("downloadCommentImages", () => {
 
     let callIndex = 0;
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="https://private-user-images.githubusercontent.com/test?jwt=token">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="https://private-user-images.githubusercontent.com/test?jwt=token">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -644,7 +652,6 @@ describe("downloadCommentImages", () => {
         "owner",
         "repo",
         comments,
-        mockFsOps,
       );
       expect(result.get(url)).toBe(
         `/tmp/github-images/image-${1704067200000 + callIndex}-0${ext}`,
@@ -665,11 +672,13 @@ describe("downloadCommentImages", () => {
 
     // Only one signed URL for two images
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl1}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl1}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -689,7 +698,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(fetchSpy).toHaveBeenCalledTimes(1);
@@ -709,11 +717,13 @@ describe("downloadCommentImages", () => {
 
     // Mock octokit response
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     // Mock fetch for image download
     const mockArrayBuffer = new ArrayBuffer(8);
@@ -735,7 +745,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(mockOctokit.rest.issues.getComment).toHaveBeenCalledWith({
@@ -776,11 +785,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/double.png?jwt=token2";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl1}"><img src="${signedUrl2}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl1}"><img src="${signedUrl2}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -800,7 +811,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(fetchSpy).toHaveBeenCalledTimes(2);
@@ -827,11 +837,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/html.jpg?jwt=token2";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl1}"><img src="${signedUrl2}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl1}"><img src="${signedUrl2}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -851,7 +863,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(fetchSpy).toHaveBeenCalledTimes(2);
@@ -874,11 +885,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/dup.png?jwt=token";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -898,7 +911,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(fetchSpy).toHaveBeenCalledTimes(1); // Only downloaded once
@@ -919,11 +931,13 @@ describe("downloadCommentImages", () => {
       "https://private-user-images.githubusercontent.com/complex.webp?jwt=token";
 
     // @ts-expect-error Mock implementation doesn't match full type signature
-    mockOctokit.rest.issues.getComment = jest.fn().mockResolvedValue({
-      data: {
-        body_html: `<img src="${signedUrl}">`,
-      },
-    });
+    mockOctokit.rest.issues.getComment = mock(() =>
+      Promise.resolve({
+        data: {
+          body_html: `<img src="${signedUrl}">`,
+        },
+      }),
+    );
 
     fetchSpy = spyOn(global, "fetch").mockResolvedValue({
       ok: true,
@@ -943,7 +957,6 @@ describe("downloadCommentImages", () => {
       "owner",
       "repo",
       comments,
-      mockFsOps,
     );
 
     expect(fetchSpy).toHaveBeenCalledTimes(1);