🧒 Explain like I'm 5
Flight simulators let pilots train for emergencies without risking real planes or passengers. The simulator is a 'mock' of a real aircraft — it behaves the same way but runs in a controlled environment. In testing, mocking swaps out real dependencies (APIs, databases, clocks) for controllable fakes. This lets you simulate 'the server returned a 500 error' or 'it is midnight on New Year's Eve' without actually breaking the server or waiting for midnight.
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Senior-level deep dive: internals, pitfalls, and a self-interview ladder.
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