The 'exitCallbacks' and 'outputCallbacks' arrays are defined and iterated over in the constructor but are never updated when callbacks are registered via onExit or onOutput. Consider either removing these arrays or updating the implementation to store and later invoke registered callbacks consistently.

The test expects a 'success' property on the result, but NoopChildProcess does not explicitly provide this. Consider adding a getter for 'success' (e.g., returning true when results.code equals 0) to align the implementation with the test expectations.

The constructor is attempting to iterate through exitCallbacks which is initialized as an empty array, so no callbacks will be executed at this point. Since callbacks are registered through the onExit method after construction, consider modifying onExit to either:

1. Execute the callback immediately if called after construction:

onExit(cb: (code: number, terminalOutput: string) => void): void {
  this.exitCallbacks.push(cb);
  // Already completed, call immediately
  cb(this.results.code, this.results.terminalOutput);
}

2. Or use setTimeout to ensure callbacks are executed asynchronously:

constructor(private results: { code: number; terminalOutput: string }) {
  setTimeout(() => {
    for (const cb of this.exitCallbacks) {
      cb(this.results.code, this.results.terminalOutput);
    }
  }, 0);
}

This will ensure proper simulation of an asynchronous process completion.

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