message: Adds comment about mockphysics.
diff: @@ -20,6 +20,7 @@ const mockNavigator = { push: route => (nextStep = route) }
  jest.useFakeTimers()
  beforeEach(() => {
  + // Because of how we mock metaphysics, the mocked value from one test can bleed into another.
  mockphysics.mockReset()
  })
  