Add strict option to xfail, making tests which XPASS to actually fail the suite

Fix #1355

_pytest/skipping.py

@@ -14,6 +14,12 @@ def pytest_addoption(parser):
            action="store_true", dest="runxfail", default=False,
            help="run tests even if they are marked xfail")
 
+    parser.addini("xfail_strict", "default for the strict parameter of xfail "
+                                  "markers when not given explicitly (default: "
+                                  "False)",
+                                  default=False,
+                                  type="bool")
+
 
 def pytest_configure(config):
     if config.option.runxfail:
@@ -178,6 +184,18 @@ def pytest_runtest_setup(item):
 
 def pytest_pyfunc_call(pyfuncitem):
     check_xfail_no_run(pyfuncitem)
+    evalxfail = pyfuncitem._evalxfail
+    if evalxfail.istrue() and _is_strict_xfail(evalxfail, pyfuncitem.config):
+        del pyfuncitem._evalxfail
+        explanation = evalxfail.getexplanation()
+        pytest.fail('[XPASS(strict)] ' + explanation,
+                    pytrace=False)
+
+
+def _is_strict_xfail(evalxfail, config):
+    default = config.getini('xfail_strict')
+    return evalxfail.get('strict', default)
+
 
 def check_xfail_no_run(item):
     if not item.config.option.runxfail:

doc/en/skipping.rst

@@ -32,12 +32,17 @@ Marking a test function to be skipped
 .. versionadded:: 2.9
 
 The simplest way to skip a test function is to mark it with the `skip` decorator
-which may be passed an optional `reason`:
+which may be passed an optional ``reason``:
+
+.. code-block:: python
 
     @pytest.mark.skip(reason="no way of currently testing this")
     def test_the_unknown():
         ...
 
+``skipif``
+~~~~~~~~~~
+
 .. versionadded:: 2.0, 2.4
 
 If you wish to skip something conditionally then you can use `skipif` instead.
@@ -120,7 +125,7 @@ Mark a test function as expected to fail
 -------------------------------------------------------
 
 You can use the ``xfail`` marker to indicate that you
-expect the test to fail::
+expect a test to fail::
 
     @pytest.mark.xfail
     def test_function():
@@ -128,14 +133,36 @@ expect the test to fail::
 
 This test will be run but no traceback will be reported
 when it fails. Instead terminal reporting will list it in the
-"expected to fail" or "unexpectedly passing" sections.
+"expected to fail" (``XFAIL``) or "unexpectedly passing" (``XPASS``) sections.
 
-By specifying on the commandline::
+``strict`` parameter
+~~~~~~~~~~~~~~~~~~~~
 
-    pytest --runxfail
+.. versionadded:: 2.9
 
-you can force the running and reporting of an ``xfail`` marked test
-as if it weren't marked at all.
+Both ``XFAIL`` and ``XPASS`` don't fail the test suite, unless the ``strict`` keyword-only
+parameter is passed as ``True``:
+
+.. code-block:: python
+
+    @pytest.mark.xfail(strict=True)
+    def test_function():
+        ...
+
+
+This will make ``XPASS`` ("unexpectedly passing") results from this test to fail the test suite.
+
+You can change the default value of the ``strict`` parameter using the
+``xfail_strict`` ini option:
+
+.. code-block:: ini
+
+    [pytest]
+    xfail_strict=true
+
+
+``reason`` parameter
+~~~~~~~~~~~~~~~~~~~~
 
 As with skipif_ you can also mark your expectation of a failure
 on a particular platform::
@@ -145,14 +172,51 @@ on a particular platform::
     def test_function():
         ...
 
+
+``raises`` parameter
+~~~~~~~~~~~~~~~~~~~~
+
 If you want to be more specific as to why the test is failing, you can specify
-a single exception, or a list of exceptions, in the ``raises`` argument. Then
-the test will be reported as a regular failure if it fails with an
+a single exception, or a list of exceptions, in the ``raises`` argument.
+
+.. code-block:: python
+
+    @pytest.mark.xfail(raises=RuntimeError)
+    def test_function():
+        ...
+
+Then the test will be reported as a regular failure if it fails with an
 exception not mentioned in ``raises``.
 
-You can furthermore prevent the running of an "xfail" test or
-specify a reason such as a bug ID or similar.  Here is
-a simple test file with the several usages:
+``run`` parameter
+~~~~~~~~~~~~~~~~~
+
+If a test should be marked as xfail and reported as such but should not be
+even executed, use the ``run`` parameter as ``False``:
+
+.. code-block:: python
+
+    @pytest.mark.xfail(run=False)
+    def test_function():
+        ...
+
+This is specially useful for marking crashing tests for later inspection.
+
+
+Ignoring xfail marks
+~~~~~~~~~~~~~~~~~~~~
+
+By specifying on the commandline::
+
+    pytest --runxfail
+
+you can force the running and reporting of an ``xfail`` marked test
+as if it weren't marked at all.
+
+Examples
+~~~~~~~~
+
+Here is a simple test file with the several usages:
 
 .. literalinclude:: example/xfail_demo.py
 
@@ -181,6 +245,19 @@ Running it with the report-on-xfail option gives this output::
 
     ======= 7 xfailed in 0.12 seconds ========
 
+
+xfail signature summary
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Here's the signature of the ``xfail`` marker, using Python 3 keyword-only
+arguments syntax:
+
+.. code-block:: python
+
+    def xfail(condition=None, *, reason=None, raises=None, run=True, strict=False):
+
+
+
 .. _`skip/xfail with parametrize`:
 
 Skip/xfail with parametrize

testing/test_skipping.py

@@ -350,6 +350,58 @@ class TestXFail:
             matchline,
         ])
 
+    @pytest.mark.parametrize('strict', [True, False])
+    def test_strict_xfail(self, testdir, strict):
+        p = testdir.makepyfile("""
+            import pytest
+
+            @pytest.mark.xfail(reason='unsupported feature', strict=%s)
+            def test_foo():
+                pass
+        """ % strict)
+        result = testdir.runpytest(p, '-rxX')
+        if strict:
+            result.stdout.fnmatch_lines([
+                '*test_foo*',
+                '*XPASS(strict)*unsupported feature*',
+            ])
+        else:
+            result.stdout.fnmatch_lines([
+                '*test_strict_xfail*',
+                'XPASS test_strict_xfail.py::test_foo unsupported feature',
+            ])
+        assert result.ret == (1 if strict else 0)
+
+    @pytest.mark.parametrize('strict', [True, False])
+    def test_strict_xfail_condition(self, testdir, strict):
+        p = testdir.makepyfile("""
+            import pytest
+
+            @pytest.mark.xfail(False, reason='unsupported feature', strict=%s)
+            def test_foo():
+                pass
+        """ % strict)
+        result = testdir.runpytest(p, '-rxX')
+        result.stdout.fnmatch_lines('*1 passed*')
+        assert result.ret == 0
+
+    @pytest.mark.parametrize('strict_val', ['true', 'false'])
+    def test_strict_xfail_default_from_file(self, testdir, strict_val):
+        testdir.makeini('''
+            [pytest]
+            xfail_strict = %s
+        ''' % strict_val)
+        p = testdir.makepyfile("""
+            import pytest
+            @pytest.mark.xfail(reason='unsupported feature')
+            def test_foo():
+                pass
+        """)
+        result = testdir.runpytest(p, '-rxX')
+        strict = strict_val == 'true'
+        result.stdout.fnmatch_lines('*1 failed*' if strict else '*1 xpassed*')
+        assert result.ret == (1 if strict else 0)
+
 
 class TestXFailwithSetupTeardown:
     def test_failing_setup_issue9(self, testdir):