Function mockCockpitFile

mockCockpitFile(
    content: string | null,
    error?: string,
): {
    read(): Promise<string | null>;
    replace(content: string): Promise<void>;
    watch(callback: (content: string | null) => void): CockpitChannel;
}
Creates a fake cockpit.file() return value.
Parameters
- content: string | null
  Initial file content. Pass null to simulate a missing file (ENOENT).
- Optionalerror: string
  When provided, read() and replace() reject with this message.
Returns {
    read(): Promise<string | null>;
    replace(content: string): Promise<void>;
    watch(callback: (content: string | null) => void): CockpitChannel;
}
Example
```
vi.spyOn(cockpit, "file").mockReturnValue(mockCockpitFile("[Unit]\nDescription=test\n"));
vi.spyOn(cockpit, "file").mockReturnValue(mockCockpitFile(null)); // missing file
```
- Defined in src/testing/helpers.ts:60