Added a failing test for PyQT plotting (passes <0.1.7, fails at later…

… versions). (#805)

* Dont assume that unit attribute exists

* Dont assume that full_name or nd_array exist either

* Added a test for pyqtgraph plot

* This may return a numpy array so explicitly chech against None

qcodes/plots/pyqtgraph.py

@@ -526,9 +526,9 @@ def fixUnitScaling(self, startranges: Optional[Dict[str, Dict[str, Union[float,i
         for i, plot in enumerate(self.subplots):
             # make a dict mapping axis labels to axis positions
             for axis in ('x', 'y', 'z'):
-                if self.traces[i]['config'].get(axis):
-                    unit = self.traces[i]['config'][axis].unit
-                    if unit not in standardunits:
+                if self.traces[i]['config'].get(axis) is not None:
+                    unit = getattr(self.traces[i]['config'][axis], 'unit', None)
+                    if unit is not None and unit not in standardunits:
                         if axis in ('x', 'y'):
                             ax = plot.getAxis(axismapping[axis])
                         else:
@@ -546,18 +546,18 @@ def fixUnitScaling(self, startranges: Optional[Dict[str, Dict[str, Union[float,i
                         ax.update()
 
                     # set limits either from dataset or
-                    setarr = self.traces[i]['config'][axis].ndarray
+                    setarr = getattr(self.traces[i]['config'][axis], 'ndarray', None)
                     arrmin = None
                     arrmax = None
-                    if not np.all(np.isnan(setarr)):
+                    if setarr and not np.all(np.isnan(setarr)):
                         arrmax = setarr.max()
                         arrmin = setarr.min()
                     elif startranges is not None:
                         try:
                             paramname = self.traces[i]['config'][axis].full_name
                             arrmax = startranges[paramname]['max']
                             arrmin = startranges[paramname]['min']
-                        except (IndexError, KeyError):
+                        except (IndexError, KeyError, AttributeError):
                             continue
 
                     if axis == 'x':

qcodes/tests/test_plots.py

@@ -6,6 +6,7 @@
     - just test "window creation"
 """
 from unittest import TestCase, skipIf
+import numpy as np
 import os
 
 try:
@@ -44,6 +45,25 @@ def test_creation(self):
         plotQ = QtPlot(remote=False, show_window=False, interval=0)
         plotQ.add_subplot()
 
+    def test_simple_plot(self):
+        plotQ = QtPlot(remote=False, show_window=False, interval=0)
+        plotQ.add_subplot()
+
+        main_QtPlot = QtPlot(
+            window_title='Main plotmon of TestQtPlot',
+            figsize=(600, 400))
+
+        x = np.arange(0, 10e-6, 1e-9)
+        f = 2e6
+        y = np.cos(2*np.pi*f*x)
+
+        for j in range(4):
+            main_QtPlot.add(x=x, y=y,
+                            xlabel='Time', xunit='s',
+                            ylabel='Amplitude', yunit='V',
+                            subplot=j+1,
+                            symbol='o', symbolSize=5)
+
 
 @skipIf(noMatPlot, '***matplotlib plotting cannot be tested***')
 class TestMatPlot(TestCase):