By default, JMock’s “context” is not thread safe. All bets are off if you access the Mockery from multiple threads. Happily, since JMock 2.6.0, you can set a threading policy per mockery.

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Mockery mockery = new JUnit4Mockery() {{
  setThreadingPolicy(new Synchroniser());
}};

The Synchroniser forces serialisation of each mocked method call using synchronized. Use it when you’re running multi-threaded style tests using JMock. The default behaviour will warn you if a mockery is being used like this.

the Mockery is not thread-safe: use a Synchroniser to ensure thread safety