diff --git a/apps/desktop/src/lib/job_runner.ts b/apps/desktop/src/lib/job_runner.ts
index 7809220e..b024ad5a 100644
--- a/apps/desktop/src/lib/job_runner.ts
+++ b/apps/desktop/src/lib/job_runner.ts
@@ -36,22 +36,16 @@ const mockWorkspace: RehearsalWorkspace = {
   workspaceVersion: 1
 };
 
-const mockSongsById = new Map<string, SongRehearsalPack>();
+const mockSongsById = new Map<string, SongRehearsalPack>(
+  mockWorkspace.songs.map(song => [song.id, song])
+);
 
 type MockListener = (event: { payload: unknown }) => void;
 const mockListeners = new Set<MockListener>();
 
 /** Documented. */
 function getMockSong(jobId: string): SongRehearsalPack | undefined {
-  const cachedPack = mockSongsById.get(jobId);
-  if (cachedPack) {
-    return cachedPack;
-  }
-  const pack = mockWorkspace.songs.find(song => song.id === jobId);
-  if (pack) {
-    mockSongsById.set(jobId, pack);
-  }
-  return pack;
+  return mockSongsById.get(jobId);
 }
 
 /**