test(desktop): keep the EIO probe case in the HostFileRead suite

Move the transient stat case into HostFileRead.test.ts behind a
pass-through fs mock (only one fixture name fails), instead of a
separate module-mocked file.

Refs #9703

Co-Authored-By: gensokyo-dev <342580529+gensokyo-dev@users.noreply.github.com>

src/desktop/HostFileRead.test.ts

@@ -1,9 +1,25 @@
 import { mkdir, chmod, symlink, writeFile } from "node:fs/promises";
 import { join } from "node:path";
 
-import { describe, expect, it } from "vitest";
+import { describe, expect, it, vi } from "vitest";
 
-import { probeHostFile } from "./HostFileRead.js";
+// Pass-through except for one name, so the transient (EIO) branch is reachable
+// without a host fault; every other probe here uses the real filesystem.
+vi.mock("node:fs/promises", async (importOriginal) => {
+  const fs = await importOriginal<typeof import("node:fs/promises")>();
+  return {
+    ...fs,
+    stat: async (...args: Parameters<typeof fs.stat>) => {
+      if (String(args[0]).endsWith("transient.so"))
+        throw Object.assign(new Error("injected I/O failure"), {
+          code: "EIO",
+        });
+      return fs.stat(...args);
+    },
+  };
+});
+
+import { hostFileKind, probeHostFile } from "./HostFileRead.js";
 import { createTestTempDirectory } from "../../tests/fixtures/temporaryDirectory.js";
 
 describe.skipIf(process.platform === "win32")("probeHostFile", () => {
@@ -33,7 +49,6 @@ describe.skipIf(process.platform === "win32")("probeHostFile", () => {
   });
 
   it("reports a readable regular file as a file", async () => {
-    // The transient (EIO) branch is covered in HostFileRead.transient.test.ts.
     const root = await createTestTempDirectory("rea-host-file-probe-");
     const path = join(root, "libcore.so");
     await writeFile(path, "carrier");
@@ -59,3 +74,12 @@ describe.skipIf(process.platform === "win32")("probeHostFile", () => {
     }
   });
 });
+
+it("keeps a transient stat failure unresolved rather than absent", async () => {
+  // EIO neither proves absence nor lets ld.so search past the candidate.
+  await expect(probeHostFile("/fixture/lib/transient.so")).resolves.toEqual({
+    kind: "unknown",
+    unreachable: false,
+  });
+  await expect(hostFileKind("/fixture/lib/transient.so")).resolves.toBeNull();
+});

src/desktop/HostFileRead.transient.test.ts

@@ -1,26 +0,0 @@
-import { expect, it, vi } from "vitest";
-
-vi.mock("node:fs/promises", async (importOriginal) => {
-  const fs = await importOriginal<typeof import("node:fs/promises")>();
-  return {
-    ...fs,
-    stat: async (...args: Parameters<typeof fs.stat>) => {
-      if (String(args[0]).endsWith("transient.so"))
-        throw Object.assign(new Error("injected I/O failure"), {
-          code: "EIO",
-        });
-      return fs.stat(...args);
-    },
-  };
-});
-
-import { hostFileKind, probeHostFile } from "./HostFileRead.js";
-
-it("keeps a transient stat failure unresolved rather than absent", async () => {
-  // EIO neither proves absence nor lets ld.so search past the candidate.
-  await expect(probeHostFile("/fixture/lib/transient.so")).resolves.toEqual({
-    kind: "unknown",
-    unreachable: false,
-  });
-  await expect(hostFileKind("/fixture/lib/transient.so")).resolves.toBeNull();
-});