DOC: Demo using pytest features in test classes

[ci skip]

Author: gfyoung

doc/source/contributing.rst

@@ -629,7 +629,7 @@ testing of many cases in a concise way that enables an easy-to-read syntax.
       class TestReallyCoolFeature(tm.TestCase):
           ....
 
-   Going forward we are moving to a more *functional* style, please see below.
+   Going forward, we are moving to a more *functional* style, please see below.
 
 
 Here is an example of a self-contained set of tests that illustrate multiple features that we like to use.
@@ -641,7 +641,7 @@ Here is an example of a self-contained set of tests that illustrate multiple fea
 - ``tm.assert_series_equal`` (and its counter part ``tm.assert_frame_equal``), for pandas object comparisons.
 - the typical pattern of constructing an ``expected`` and comparing versus the ``result``
 
-We would name this file ``test_cool_feature.py`` and put in an appropriate place in the ``pandas/tests/`` sturcture.
+We would name this file ``test_cool_feature.py`` and put in an appropriate place in the ``pandas/tests/`` structure.
 
 .. code-block:: python
 
@@ -701,6 +701,18 @@ Tests that we have ``parametrized`` are now accessible via the test name, for ex
    test_cool_feature.py::test_dtypes[int8] PASSED
    test_cool_feature.py::test_series[int8] PASSED
 
+Sometimes, it does make sense to bundle test functions together into a single class, either because the test file is testing multiple functions from a single module, and
+using test classes allows for better organization. However, instead of inheriting from ``tm.TestCase``, we just inherit from ``object``, and we can parametrize as before:
+
+
+.. code-block:: python
+
+    class TestReallyCoolFeature(object):
+
+        @pytest.mark.parametrize('dtype', ['int8', 'int16', 'int32', 'int64'])
+        def test_dtypes(self, dtype):
+            assert str(np.dtype(dtype)) == dtype
+
 
 Running the test suite
 ----------------------