Merge pull request #2881 from dawran6/2658

Document pytest.param

AUTHORS

@@ -46,6 +46,7 @@ Dave Hunt
 David Díaz-Barquero
 David Mohr
 David Vierra
+Daw-Ran Liou
 Denis Kirisov
 Diego Russo
 Dmitry Dygalo

changelog/2658.doc

@@ -0,0 +1 @@
+Append example for pytest.param in the example/parametrize document.

doc/en/example/parametrize.rst

@@ -485,4 +485,54 @@ of our ``test_func1`` was skipped.  A few notes:
   values as well.
 
 
+Set marks or test ID for individual parametrized test
+--------------------------------------------------------------------
 
+Use ``pytest.param`` to apply marks or set test ID to individual parametrized test.
+For example::
+
+    # content of test_pytest_param_example.py
+    import pytest
+    @pytest.mark.parametrize('test_input,expected', [
+        ('3+5', 8),
+        pytest.param('1+7', 8,
+                     marks=pytest.mark.basic),
+        pytest.param('2+4', 6,
+                     marks=pytest.mark.basic,
+                     id='basic_2+4'),
+        pytest.param('6*9', 42,
+                     marks=[pytest.mark.basic, pytest.mark.xfail],
+                     id='basic_6*9'),
+    ])
+    def test_eval(test_input, expected):
+        assert eval(test_input) == expected
+    
+In this example, we have 4 parametrized tests. Except for the first test,
+we mark the rest three parametrized tests with the custom marker ``basic``,
+and for the fourth test we also use the built-in mark ``xfail`` to indicate this 
+test is expected to fail. For explicitness, we set test ids for some tests.
+
+Then run ``pytest`` with verbose mode and with only the ``basic`` marker::
+
+    pytest -v -m basic
+    ============================================ test session starts =============================================
+    platform linux -- Python 3.x.y, pytest-3.x.y, py-1.x.y, pluggy-0.x.y
+    rootdir: $REGENDOC_TMPDIR, inifile:
+    collected 4 items
+
+    test_pytest_param_example.py::test_eval[1+7-8] PASSED
+    test_pytest_param_example.py::test_eval[basic_2+4] PASSED
+    test_pytest_param_example.py::test_eval[basic_6*9] xfail
+    ========================================== short test summary info ===========================================
+    XFAIL test_pytest_param_example.py::test_eval[basic_6*9]
+
+    ============================================= 1 tests deselected =============================================
+
+As the result:
+
+- Four tests were collected
+- One test was deselected because it doesn't have the ``basic`` mark.
+- Three tests with the ``basic`` mark was selected.
+- The test ``test_eval[1+7-8]`` passed, but the name is autogenerated and confusing.
+- The test ``test_eval[basic_2+4]`` passed.
+- The test ``test_eval[basic_6*9]`` was expected to fail and did fail.