Improve test mocking to actually capture failure mode.

IPython/core/tests/test_pylabtools.py

@@ -1,128 +1,139 b''
 """Tests for pylab tools module.
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2011, the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 from __future__ import print_function
 
 # Stdlib imports
 
 # Third-party imports
 import matplotlib; matplotlib.use('Agg')
 import nose.tools as nt
 
 from matplotlib import pyplot as plt
 import numpy as np
 
 # Our own imports
 from IPython.testing import decorators as dec
 from .. import pylabtools as pt
 
 #-----------------------------------------------------------------------------
 # Globals and constants
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Local utilities
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Classes and functions
 #-----------------------------------------------------------------------------
 
 @dec.parametric
 def test_figure_to_svg():
     # simple empty-figure test
     fig = plt.figure()
     yield nt.assert_equal(pt.print_figure(fig, 'svg'), None)
 
     plt.close('all')
 
     # simple check for at least svg-looking output
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
     svg = pt.print_figure(fig, 'svg')[:100].lower()
     yield nt.assert_true('doctype svg' in svg)
 
 
 def test_import_pylab():
     ip = get_ipython()
     ns = {}
     pt.import_pylab(ns, import_all=False)
     nt.assert_true('plt' in ns)
     nt.assert_equal(ns['np'], np)
 
 
 class TestPylabSwitch(object):
     class Shell(object):
         pylab_gui_select = None
 
     def setup(self):
+        import matplotlib
+        def act_mpl(backend):
+            matplotlib.rcParams['backend'] = backend
+
+        # Save rcParams since they get modified
+        self._saved_rcParams = matplotlib.rcParams
+        matplotlib.rcParams = dict(backend='Qt4Agg')
+
+        # Mock out functions
         self._save_am = pt.activate_matplotlib
-        pt.activate_matplotlib = lambda *a,**kw:None
+        pt.activate_matplotlib = act_mpl
         self._save_ip = pt.import_pylab
         pt.import_pylab = lambda *a,**kw:None
         self._save_cis = pt.configure_inline_support
         pt.configure_inline_support = lambda *a,**kw:None
 
     def teardown(self):
         pt.activate_matplotlib = self._save_am
         pt.import_pylab = self._save_ip
         pt.configure_inline_support = self._save_cis
+        import matplotlib
+        matplotlib.rcParams = self._saved_rcParams
 
     def test_qt(self):
         s = self.Shell()
-        gui = pt.pylab_activate(dict(), 'qt', False, s)
+        gui = pt.pylab_activate(dict(), None, False, s)
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui = pt.pylab_activate(dict(), 'inline', False, s)
         nt.assert_equal(gui, 'inline')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
-        gui = pt.pylab_activate(dict(), None, False, s)
+        gui = pt.pylab_activate(dict(), 'qt', False, s)
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui = pt.pylab_activate(dict(), 'inline', False, s)
         nt.assert_equal(gui, 'inline')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui = pt.pylab_activate(dict(), None, False, s)
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
     def test_inline(self):
         s = self.Shell()
         gui = pt.pylab_activate(dict(), 'inline', False, s)
         nt.assert_equal(gui, 'inline')
         nt.assert_equal(s.pylab_gui_select, None)
 
         gui = pt.pylab_activate(dict(), 'inline', False, s)
         nt.assert_equal(gui, 'inline')
         nt.assert_equal(s.pylab_gui_select, None)
 
         gui = pt.pylab_activate(dict(), 'qt', False, s)
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
     def test_qt_gtk(self):
         s = self.Shell()
         gui = pt.pylab_activate(dict(), 'qt', False, s)
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui = pt.pylab_activate(dict(), 'gtk', False, s)
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')