create base class MeasurementData for ADC_Result and Accumulation

tests/test_ADC_Result.py

@@ -30,6 +30,21 @@ class TestADCResult(unittest.TestCase):
         self.assertEqual(len(adc.x), 0)
         self.assertEqual(len(adc.y), 0)
 
+    def test_shared_measurement_statistics(self):
+        adc = self.create_adc_result()
+        np.testing.assert_allclose(adc.get_ymean(), [20, 25])
+        np.testing.assert_allclose(adc.get_ymin_channels(), [10, 15])
+        np.testing.assert_allclose(adc.get_ymax_channels(), [30, 35])
+        np.testing.assert_allclose(adc.get_yrms(),
+                                   [np.sqrt(np.mean(np.array([10, 20, 30]) ** 2)),
+                                    np.sqrt(np.mean(np.array([15, 25, 35]) ** 2))])
+        np.testing.assert_allclose(adc.get_ystd(), [np.std([10, 20, 30]),
+                                                    np.std([15, 25, 35])])
+
+    def test_shared_phase_uses_public_channel_values(self):
+        adc = self.create_adc_result()
+        self.assertAlmostEqual(adc.get_phase(), np.degrees(np.arctan2(15, 10)))
+
     def test_constructor_with_arguments(self):
         """Test initializer with all arguments."""
         x = np.array([0.0, 1.0, 2.0])