fix to_glue method, add test

.travis.yml

@@ -27,6 +27,7 @@ env:
     MOCK=mock
     NOSETIMER=nose-timer
     REQUESTS=requests
+    GLUE=glueviz
 
 before_install:
   - |
@@ -55,7 +56,7 @@ install:
     pip install --upgrade wheel
     pip install --upgrade setuptools
     # Install dependencies
-    pip install $MOCK $NUMPY $SCIPY $H5PY $CYTHON $MATPLOTLIB $SYMPY $FASTCACHE $IPYTHON $FLAKE8 $CODECOV $COVERAGE $PANDAS $NOSE $NOSETIMER $REQUESTS
+    pip install $MOCK $NUMPY $SCIPY $H5PY $CYTHON $MATPLOTLIB $SYMPY $FASTCACHE $IPYTHON $FLAKE8 $CODECOV $COVERAGE $PANDAS $NOSE $NOSETIMER $REQUESTS $GLUE
     # install yt
     if [[ $TRAVIS_BUILD_STAGE_NAME != "Lint" ]]; then
       pip install -e .

yt/data_objects/data_containers.py

@@ -637,20 +637,29 @@ def to_glue(self, fields, label="yt", data_collection=None):
         the Glue environment, you can pass a *data_collection* object,
         otherwise Glue will be started.
         """
+        from yt.config import ytcfg
         from glue.core import DataCollection, Data
-        try:
-            from glue.app.qt.application import GlueApplication
-        except ImportError:
-            from glue.qt.glue_application import GlueApplication
-
+        if ytcfg.getboolean("yt", "__withintesting"):
+            from glue.core.application_base import \
+                Application as GlueApplication
+        else:
+            try:
+                from glue.app.qt.application import GlueApplication
+            except ImportError:
+                from glue.qt.glue_application import GlueApplication
         gdata = Data(label=label)
         for component_name in fields:
             gdata.add_component(self[component_name], component_name)
 
         if data_collection is None:
             dc = DataCollection([gdata])
             app = GlueApplication(dc)
-            app.start()
+            try:
+                app.start()
+            except AttributeError:
+                # In testing we're using a dummy glue application object
+                # that doesn't have a start method
+                pass
         else:
             data_collection.append(gdata)
 

yt/data_objects/tests/test_glue.py

@@ -0,0 +1,13 @@
+import nose
+
+from yt.config import ytcfg
+from yt.testing import fake_random_ds
+
+def setup_func():
+    ytcfg["yt", "__withintesting"] = "True"
+
+@nose.with_setup(setup_func)
+def test_glue_data_object():
+    ds = fake_random_ds(16)
+    ad = ds.all_data()
+    ad.to_glue([('gas', 'density')])