Add simple tests to ensure plugins are imported

Author: mattwthompson

mbuild/tests/test_plugins.py

@@ -0,0 +1,16 @@
+import pytest
+
+from mbuild.tests.base_test import BaseTest
+
+
+class TestPlugins(BaseTest):
+    def test_basic_import(self):
+        import mbuild.recipes
+
+    @pytest.mark.parametrize(
+        'recipe_name',
+        ['Monolayer', 'Polymer', 'SilicaInterface', 'TiledCompound'],
+    )
+    def test_recipes_contents(self, recipe_name):
+        import mbuild.recipes
+        recipe_name in dir(mbuild.recipes)