Testing: add isinstance asserts to plot tests

Add several checks to ensure that the plot object returned by a
get_xxx_plot() call has the expected class. These were not made
before because the mocking done to support chips testing meant that
the tests would fail (thanks to the mocking). As this has now been
removed add back the instance checks.

Note that these tests don't really add that much, so they are not
essential.

sherpa/astro/ui/tests/test_astro_ui_plot.py

@@ -1,5 +1,5 @@
 #
-#  Copyright (C) 2019  Smithsonian Astrophysical Observatory
+#  Copyright (C) 2019, 2020  Smithsonian Astrophysical Observatory
 #
 #
 #  This program is free software; you can redistribute it and/or modify
@@ -34,9 +34,8 @@
 
 from sherpa.astro import ui
 
-# the chips plot tests mean that we can't test the plot instances
-# (because of the mocking that the chips tests do)
-# from sherpa.plot import DataPlot, FitPlot, ModelPlot
+from sherpa.astro.plot import ARFPlot, BkgDataPlot, ModelHistogram, \
+    SourcePlot
 
 from sherpa.utils.err import IdentifierErr
 from sherpa.utils.testing import requires_data, requires_fits, \
@@ -252,12 +251,6 @@ def setup_example_bkg_model(idval):
 """
 
 
-# The following tests do not check whether returned values are
-# of the expected class instance, since the chips plot tests
-# use a mock object and so mess-up simple "isinstance(x, ModelPlot)"
-# checks.
-#
-
 @pytest.mark.usefixtures("clean_astro_ui")
 @pytest.mark.parametrize("idval", [None, 1, "one", 23])
 def test_get_arf_plot(idval):
@@ -270,6 +263,8 @@ def test_get_arf_plot(idval):
     else:
         ap = ui.get_arf_plot(idval)
 
+    assert isinstance(ap, ARFPlot)
+
     assert ap.xlo == pytest.approx(_energies[:-1])
     assert ap.xhi == pytest.approx(_energies[1:])
 
@@ -294,6 +289,8 @@ def test_get_bkg_plot(idval):
     else:
         bp = ui.get_bkg_plot(idval)
 
+    assert isinstance(bp, BkgDataPlot)
+
     assert bp.x == pytest.approx(_data_chan)
 
     # normalise by exposure time and bin width, but bin width here
@@ -376,6 +373,8 @@ def test_get_model_plot(idval):
     else:
         mp = ui.get_model_plot(idval)
 
+    assert isinstance(mp, ModelHistogram)
+
     assert mp.xlo == pytest.approx(_data_chan)
     assert mp.xhi == pytest.approx(_data_chan + 1)
 
@@ -462,6 +461,8 @@ def test_get_source_plot_energy(idval):
         ui.set_analysis(idval, 'energy')
         sp = ui.get_source_plot(idval)
 
+    assert isinstance(sp, SourcePlot)
+
     assert sp.xlo == pytest.approx(_energies[:-1])
     assert sp.xhi == pytest.approx(_energies[1:])
 

sherpa/ui/tests/test_ui_plot.py

@@ -1,5 +1,5 @@
 #
-#  Copyright (C) 2019  Smithsonian Astrophysical Observatory
+#  Copyright (C) 2019, 2020  Smithsonian Astrophysical Observatory
 #
 #
 #  This program is free software; you can redistribute it and/or modify
@@ -24,8 +24,7 @@
 
 from sherpa import ui
 
-# the chips plot tests mean that we can't test the plot instances
-# from sherpa.plot import DataPlot, FitPlot, ModelPlot
+from sherpa.plot import DataPlot, FitPlot, ModelPlot
 
 from sherpa.stats import Chi2Gehrels
 from sherpa.utils.testing import requires_plotting
@@ -100,15 +99,9 @@ def test_get_fit_plot(idval):
     else:
         f = ui.get_fit_plot(idval)
 
-    # Should we be checking exact class?
-    #
-    # No - because the mock_chips pytest routine redefines these
-    # classes and so makes the test fail (or at least that's my
-    # assumption).
-    #
-    # assert isinstance(f, FitPlot)
-    # assert isinstance(f.dataplot, DataPlot)
-    # assert isinstance(f.modelplot, ModelPlot)
+    assert isinstance(f, FitPlot)
+    assert isinstance(f.dataplot, DataPlot)
+    assert isinstance(f.modelplot, ModelPlot)
 
     dp = f.dataplot
     mp = f.modelplot