Merge pull request #123 from enthought/enh-path-assertion-methods

Add assert methods for drawing and compiled paths

enable/testing.py

@@ -4,6 +4,8 @@
 
 from enable.abstract_window import AbstractWindow
 from enable.events import MouseEvent, KeyEvent
+from kiva.testing import KivaTestAssistant
+
 
 class _MockWindow(AbstractWindow):
 
@@ -15,7 +17,7 @@ def _redraw(self, coordinates=None):
         pass
 
 
-class EnableTestAssistant(object):
+class EnableTestAssistant(KivaTestAssistant):
     """ Mixin helper for enable/chaco components.
 
     """

kiva/testing.py

@@ -0,0 +1,85 @@
+# Copyright (c) 2008-2013 by Enthought, Inc.
+# All rights reserved.
+from mock import Mock
+
+from kiva.image import GraphicsContext
+
+
+class KivaTestAssistant(object):
+    """ Mixin test helper for kiva drawing tests.
+
+    """
+
+    def create_mock_gc(
+            self, width, height, methods=()):
+        """ Create an image graphics context that with mocked methods.
+
+        Parameters
+        ----------
+        width, height :
+            The size of the graphics context canvas.
+
+        methods : iterable
+           the methods which are going to be mocked with a Mock object.
+
+        """
+        gc = GraphicsContext((int(width), int(height)))
+        gc.clear((0.0, 0.0, 0.0, 0.0))
+        for method in methods:
+            setattr(gc, method, Mock())
+        return gc
+
+    def assertPathsAreProcessed(self, drawable, width=200, height=200):
+        """ Check that all the paths have been compiled and processed.
+
+        Parameters
+        ----------
+        drawable :
+            A drawable object that has a draw method.
+
+        width : int, optional
+            The width of the array buffer (default is 200).
+
+        height : int, optional
+            The height of the array buffer (default is 200).
+
+        note ::
+
+           A drawable that draws nothing will pass this check.
+
+        """
+        gc = GraphicsContext((width, height))
+        drawable.draw(gc)
+        compiled_path = gc._get_path()
+        total_vertices = compiled_path.total_vertices()
+        self.assertEqual(
+            total_vertices, 0,
+            msg='There are {0} vertices in compiled paths {1} that '
+            'have not been processed'.format(total_vertices, compiled_path))
+
+    def assertPathsAreCreated(self, drawable, width=200, height=200):
+        """ Check that drawing creates paths.
+
+        When paths and lines creation methods are used from a graphics
+        context the drawing paths are compiled and processed. By using
+        a mock graphics context we can check if something has been drawn.
+
+        Parameters
+        ----------
+        drawable :
+            A drawable object that has a draw method.
+
+        width : int, optional
+            The width of the array buffer (default is 200).
+
+        height : int, optional
+            The height of the array buffer (default is 200).
+
+        """
+        gc = self.create_mock_gc(width, height, ('draw_path', 'stroke_path'))
+        drawable.draw(gc)
+        compiled_path = gc._get_path()
+        self.assertTrue(
+            compiled_path.total_vertices() > 0,
+            msg='There are no compiled paths '
+            'created: {0}'.format(compiled_path))

kiva/tests/test_kiva_test_assistant.py

@@ -0,0 +1,55 @@
+import unittest
+
+from kiva.testing import KivaTestAssistant
+
+
+class Drawable(object):
+
+    def __init__(self, should_draw=True, should_process=True):
+        self.should_draw = should_draw
+        self.should_process = should_process
+
+    def draw(self, gc):
+        with gc:
+            if self.should_draw:
+                gc.move_to(-5,0)
+                gc.line_to(5,0)
+                gc.move_to(0,5)
+                gc.line_to(0,-5)
+                gc.move_to(0,0)
+                # The path will not be processed and remain in the gc cache
+                # if we do not execute the stroke_path command.
+                if self.should_process:
+                    gc.stroke_path()
+
+
+class TestKivaTestAssistant(KivaTestAssistant, unittest.TestCase):
+
+    def test_path_created_assertions(self):
+        drawable = Drawable(should_draw=False)
+
+        # drawing nothing
+        self.assertRaises(AssertionError,
+            self.assertPathsAreCreated,
+            drawable)
+
+        #drawing something
+        drawable.should_draw = True
+        self.assertPathsAreCreated(drawable)
+
+    def test_paths_processed_assertions(self):
+        drawable = Drawable(should_draw=True, should_process=False)
+
+        # not finishing the path
+        self.assertRaises(
+            AssertionError,
+            self.assertPathsAreProcessed,
+            drawable)
+
+        #drawing something
+        drawable.should_process = True
+        self.assertPathsAreProcessed(drawable)
+
+
+if __name__ == '__main__':
+    unittest.main()