title: How can the return value of an OCMock stub be changed?
body: <p>It seems that the first time I add <em>andReturnValue</em> on an OCMock stub, that return value is set in stone. For example:</p>
  
  <pre><code>id physics = [OCMockObject niceMockForClass:[DynamicPhysicsComponent class]
  Entity *testEntity = [Entity entityWithPhysicsComponent:physics];
  CGPoint velocity1 = CGPointMake(100, 100);
  CGPoint velocity2 = CGPointZero;
  [[[physics stub] andReturnValue:OCMOCK_VALUE(velocity1)] getCurrentVelocity];
  [testEntity update:0.1];
  [[[physics stub] andReturnValue:OCMOCK_VALUE(velocity2)] getCurrentVelocity];
  [testEntity update:0.1];
  </code></pre>
  
  <p>The stubbed method is called in [testEntity update]. But each time the stubbed method is returning the velocity1 value, so I guess the second attempt to set the methods return value isn't honoured.</p>
  
  <p>Is there a way to do do this in OCMock?</p>