add new parameters:

xfail(run=False) will not run expected-to-fail tests
xfail(reason=True) will report the specified reason

--HG--
branch : trunk

testing/plugin/test_pytest_resultlog.py

@@ -159,6 +159,9 @@ def test_generic(testdir, LineMatcher):
         @py.test.mark.xfail
         def test_xfail():
             assert 0
+        @py.test.mark.xfail(run=False)
+        def test_xfail_norun():
+            assert 0
     """)
     testdir.runpytest("--resultlog=result.log")
     lines = testdir.tmpdir.join("result.log").readlines(cr=0)
@@ -167,5 +170,6 @@ def test_generic(testdir, LineMatcher):
         "F *:test_fail", 
         "s *:test_skip",
         "x *:test_xfail", 
+        "x *:test_xfail_norun", 
     ])
     

testing/plugin/test_pytest_skipping.py

@@ -12,6 +12,30 @@ def test_xfail_not_report_default(testdir):
         "*1 expected failures*--report=xfailed*",
     ])
 
+def test_xfail_not_run(testdir):
+    p = testdir.makepyfile(test_one="""
+        import py
+        @py.test.mark.xfail(run=False, reason="noway")
+        def test_this():
+            assert 0
+        @py.test.mark.xfail("True", run=False, reason="noway")
+        def test_this_true():
+            assert 0
+        @py.test.mark.xfail("False", run=True, reason="huh")
+        def test_this_false():
+            assert 1
+    """)
+    result = testdir.runpytest(p, '-v')
+    result.stdout.fnmatch_lines([
+        "*2 expected failures*--report=xfailed*",
+        "*1 passed*",
+    ])
+    result = testdir.runpytest(p, '--report=xfailed', )
+    result.stdout.fnmatch_lines([
+        "*test_one*test_this*not run*noway",
+        "*test_one*test_this_true*not run*noway",
+    ])
+
 def test_skip_not_report_default(testdir):
     p = testdir.makepyfile(test_one="""
         import py