@Test public void shouldProvideAvgForEachStream() { MeasurementStream stream = mock(MeasurementStream.class); when(stream.getAvg()).thenReturn(10.0); String name = sensor.getSensorName(); when(stream.getSensorName()).thenReturn(name); sessionManager.session.add(stream); assertThat(sessionManager.getAvg(sensor), equalTo(10.0)); }