Add base viewer test class, including test for unique class.

glue_plotly/viewers/common/tests/__init__.py

@@ -0,0 +1 @@
+from .base_viewer_tests import BasePlotlyViewTests  # noqa

glue_plotly/viewers/common/tests/base_viewer_tests.py

@@ -0,0 +1,22 @@
+from uuid import UUID
+
+
+class BasePlotlyViewTests:
+
+    def setup_method(self, method):
+        pass
+
+    def teardown_method(self, method):
+        pass
+
+    def test_unique_class(self):
+        unique_class = self.viewer.unique_class
+        prefix = "glue-plotly-"
+        prefix_len = len(prefix)
+        assert unique_class.startswith(prefix)
+        assert len(unique_class) == prefix_len + 32
+
+        # Test UUID validity by seeing if we can construct a UUID instance
+        assert UUID(unique_class[prefix_len:])
+
+        assert unique_class in self.viewer.figure._dom_classes

glue_plotly/viewers/histogram/tests/test_viewer.py

@@ -3,10 +3,11 @@
 from plotly.graph_objects import Bar
 
 from glue_plotly.common import DEFAULT_FONT
+from glue_plotly.viewers.common.tests import BasePlotlyViewTests
 from glue_plotly.viewers.histogram import PlotlyHistogramView
 
 
-class TestHistogramViewer:
+class TestHistogramViewer(BasePlotlyViewTests):
 
     def setup_method(self, method):
         self.data = Data(label="histogram", x=[1, 1, 1, 2, 2, 3, 3, 3, 4, 6, 6])

glue_plotly/viewers/scatter/tests/test_viewer.py

@@ -5,12 +5,14 @@
 from plotly.graph_objects import Scatter
 
 from glue_plotly.common import DEFAULT_FONT
+from glue_plotly.viewers.common.tests import BasePlotlyViewTests
 from glue_plotly.viewers.scatter import PlotlyScatterView
 
 
-class TestScatterView:
+class TestScatterView(BasePlotlyViewTests):
 
     def setup_method(self, method):
+        super().setup_method(method)
         self.data = Data(label="histogram", x=[1, 3, 5, 7, 9], y=[2, 4, 6, 8, 10])
         self.app = JupyterApplication()
         self.app.session.data_collection.append(self.data)
@@ -33,6 +35,7 @@ def setup_method(self, method):
     def teardown_method(self, method):
         self.viewer = None
         self.app = None
+        super().teardown_method(method)
 
     def test_basic(self):
         assert len(self.viewer.layers) == 1