Better xfail mechanism

Author: nedbat

tests/coveragetest.py

@@ -101,10 +101,6 @@ def setUp(self):
         self.last_command_output = None
         self.last_module_name = None
 
-    def xfail(self, msg):
-        """Mark this test as an expected failure."""
-        pytest.xfail(msg)
-
     def clean_local_file_imports(self):
         """Clean up the results of calls to `import_local_file`.
 
@@ -501,3 +497,8 @@ def command_line(args):
     script = CoverageScript()
     ret = script.command_line(shlex.split(args))
     return ret
+
+
+def xfail(condition, reason):
+    """A decorator to mark as test as expected to fail."""
+    return pytest.mark.xfail(condition, reason=reason, strict=True)

tests/test_arcs.py

@@ -3,7 +3,7 @@
 
 """Tests for coverage.py's arc measurement."""
 
-from tests.coveragetest import CoverageTest
+from tests.coveragetest import CoverageTest, xfail
 
 import coverage
 from coverage import env
@@ -629,9 +629,8 @@ def test_finally_in_loop(self):
         )
 
 
+    @xfail(env.PYBEHAVIOR.bpo39114, reason="https://bugs.python.org/issue39114")
     def test_break_through_finally(self):
-        if env.PYBEHAVIOR.bpo39114:
-            self.xfail("https://bugs.python.org/issue39114")
         if env.PYBEHAVIOR.finally_jumps_back:
             arcz = ".1 12 23 34 3D 45 56 67 68 7A 7D 8A A3 A7 BC CD D."
         else:
@@ -655,9 +654,8 @@ def test_break_through_finally(self):
             arcz_missing="3D BC CD",
         )
 
+    @xfail(env.PYBEHAVIOR.bpo39114, "https://bugs.python.org/issue39114")
     def test_continue_through_finally(self):
-        if env.PYBEHAVIOR.bpo39114:
-            self.xfail("https://bugs.python.org/issue39114")
         if env.PYBEHAVIOR.finally_jumps_back:
             arcz = ".1 12 23 34 3D 45 56 67 68 73 7A 8A A3 A7 BC CD D."
         else:
@@ -694,9 +692,8 @@ def test_finally_in_loop_bug_92(self):
             arcz=".1 12 23 35 56 61 17 7.",
         )
 
+    @xfail(env.PYBEHAVIOR.bpo39114, "https://bugs.python.org/issue39114")
     def test_bug_212(self):
-        if env.PYBEHAVIOR.bpo39114:
-            self.xfail("https://bugs.python.org/issue39114")
         # "except Exception as e" is crucial here.
         # Bug 212 said that the "if exc" line was incorrectly marked as only
         # partially covered.
@@ -818,9 +815,8 @@ def test_multiple_except_clauses(self):
             arcz_unpredicted="45 7A AB",
         )
 
+    @xfail(env.PYBEHAVIOR.bpo39114, "https://bugs.python.org/issue39114")
     def test_return_finally(self):
-        if env.PYBEHAVIOR.bpo39114:
-            self.xfail("https://bugs.python.org/issue39114")
         if env.PYBEHAVIOR.finally_jumps_back:
             arcz = ".1 12 29 9A AB BC C-1   -23 34 45 5-2 57 75 38 8-2"
         else:
@@ -842,9 +838,8 @@ def check_token(data):
             arcz=arcz,
         )
 
+    @xfail(env.PYBEHAVIOR.bpo39114, "https://bugs.python.org/issue39114")
     def test_except_jump_finally(self):
-        if env.PYBEHAVIOR.bpo39114:
-            self.xfail("https://bugs.python.org/issue39114")
         if env.PYBEHAVIOR.finally_jumps_back:
             arcz = (
                 ".1 1Q QR RS ST TU U. "
@@ -898,9 +893,8 @@ def func(x):
             arcz_unpredicted="67",
         )
 
+    @xfail(env.PYBEHAVIOR.bpo39114, "https://bugs.python.org/issue39114")
     def test_else_jump_finally(self):
-        if env.PYBEHAVIOR.bpo39114:
-            self.xfail("https://bugs.python.org/issue39114")
         if env.PYBEHAVIOR.finally_jumps_back:
             arcz = (
                 ".1 1S ST TU UV VW W. "
@@ -1522,9 +1516,8 @@ async def print_sum(x, y):                      # 8
         )
         self.assertEqual(self.stdout(), "Compute 1 + 2 ...\n1 + 2 = 3\n")
 
+    @xfail(env.PYVERSION == (3, 9, 0, 'alpha', 2, 0), "https://bugs.python.org/issue39166")
     def test_async_for(self):
-        if env.PYVERSION == (3, 9, 0, 'alpha', 2, 0):
-            self.xfail("https://bugs.python.org/issue39166")
         self.check_coverage("""\
             import asyncio
 

tests/test_parser.py

@@ -9,7 +9,7 @@
 from coverage.misc import NotPython
 from coverage.parser import PythonParser
 
-from tests.coveragetest import CoverageTest
+from tests.coveragetest import CoverageTest, xfail
 from tests.helpers import arcz_to_arcs
 
 
@@ -137,9 +137,12 @@ def test_token_error(self):
                 '''
                 """)
 
+
+    @xfail(
+        env.PYPY3 and env.PYPYVERSION >= (7, 3, 0),
+        "https://bitbucket.org/pypy/pypy/issues/3139",
+    )
     def test_decorator_pragmas(self):
-        if env.PYPY3 and env.PYPYVERSION >= (7, 3, 0):      # pragma: obscure
-            self.xfail("https://bitbucket.org/pypy/pypy/issues/3139")
         parser = self.parse_source("""\
             # 1
 

tests/test_process.py

@@ -23,7 +23,7 @@
 from coverage.files import python_reported_file
 from coverage.misc import output_encoding
 
-from tests.coveragetest import CoverageTest, TESTS_DIR
+from tests.coveragetest import CoverageTest, TESTS_DIR, xfail
 from tests.helpers import re_lines
 
 
@@ -742,12 +742,14 @@ def test_fullcoverage(self):                        # pragma: no metacov
         # about 5.
         self.assertGreater(line_counts(data)['os.py'], 50)
 
+    @xfail(
+        env.PYPY3 and env.PYPYVERSION >= (7, 1, 1),
+        "https://bitbucket.org/pypy/pypy/issues/3074"
+    )
     def test_lang_c(self):
         if env.JYTHON:
             # Jython as of 2.7.1rc3 won't compile a filename that isn't utf8.
             self.skipTest("Jython can't handle this test")
-        if env.PYPY3 and env.PYPYVERSION >= (7, 1, 1):          # pragma: obscure
-            self.xfail("https://bitbucket.org/pypy/pypy/issues/3074")
         # LANG=C forces getfilesystemencoding on Linux to 'ascii', which causes
         # failures with non-ascii file names. We don't want to make a real file
         # with strange characters, though, because that gets the test runners