create base class MeasurementData for ADC_Result and Accumulation

tests/test_Accumulation.py

@@ -33,6 +33,14 @@ class TestAccumulation(unittest.TestCase):
         self.assertEqual(len(accu.x), 0)
         self.assertEqual(len(accu.y), 0)
 
+    def test_shared_measurement_statistics_use_accumulation_means(self):
+        accu = Accumulation()
+        accu += self.create_adc_result()
+        np.testing.assert_allclose(accu.get_ymean(), [20, 25])
+        np.testing.assert_allclose(accu.get_ymin_channels(), [10, 15])
+        np.testing.assert_allclose(accu.get_ymax_channels(), [30, 35])
+        self.assertAlmostEqual(accu.get_phase(), np.degrees(np.arctan2(15, 10)), places=6)
+
     def test_constructor_with_arguments(self):
         """Test initializer with all arguments."""
         x = np.array([0.0, 1.0, 2.0])