Fixed collection of classes with custom __new__ method

AUTHORS

@@ -34,6 +34,7 @@ Dave Hunt
 David Díaz-Barquero
 David Mohr
 David Vierra
+Dmitry Dygalo
 Edison Gustavo Muenz
 Eduardo Schettino
 Elizaveta Shashkova

CHANGELOG.rst

@@ -49,6 +49,10 @@
 * ImportErrors in plugins now are a fatal error instead of issuing a
   pytest warning (`#1479`_). Thanks to `@The-Compiler`_ for the PR.
 
+* Fixed collection of classes with custom ``__new__`` method.
+  Fixes (`#1579`_). Thanks to `@Stranger6667`_ for the PR.
+
+.. _#1579: https://github.com/pytest-dev/pytest/issues/1579
 .. _#1580: https://github.com/pytest-dev/pytest/pull/1580
 .. _#1605: https://github.com/pytest-dev/pytest/issues/1605
 .. _#1597: https://github.com/pytest-dev/pytest/pull/1597
@@ -67,7 +71,7 @@
 .. _@bagerard: https://github.com/bagerard
 .. _@davehunt: https://github.com/davehunt
 .. _@DRMacIver: https://github.com/DRMacIver
-
+.. _@Stranger6667: https://github.com/Stranger6667
 
 2.9.2
 =====

_pytest/python.py

@@ -662,6 +662,10 @@ def collect(self):
             self.warn("C1", "cannot collect test class %r because it has a "
                 "__init__ constructor" % self.obj.__name__)
             return []
+        elif hasnew(self.obj):
+            self.warn("C1", "cannot collect test class %r because it has a "
+                            "__new__ constructor" % self.obj.__name__)
+            return []
         return [self._getcustomclass("Instance")(name="()", parent=self)]
 
     def setup(self):
@@ -679,8 +683,7 @@ def setup(self):
 
 class Instance(PyCollector):
     def _getobj(self):
-        obj = self.parent.obj()
-        return obj
+        return self.parent.obj()
 
     def collect(self):
         self.session._fixturemanager.parsefactories(self)
@@ -793,9 +796,13 @@ def getcallargs(self, obj):
 def hasinit(obj):
     init = getattr(obj, '__init__', None)
     if init:
-        if init != object.__init__:
-            return True
+        return init != object.__init__
+
 
+def hasnew(obj):
+    new = getattr(obj, '__new__', None)
+    if new:
+        return new != object.__new__
 
 
 def fillfixtures(function):

testing/python/collect.py

@@ -109,6 +109,18 @@ def __getattr__(self, name):
         colitems = modcol.collect()
         assert len(colitems) == 0
 
+    def test_issue1579_namedtuple(self, testdir):
+        testdir.makepyfile("""
+            import collections
+
+            TestCase = collections.namedtuple('TestCase', ['a'])
+        """)
+        result = testdir.runpytest('-rw')
+        result.stdout.fnmatch_lines(
+            "*cannot collect test class 'TestCase' "
+            "because it has a __new__ constructor*"
+        )
+
 
 class TestGenerator:
     def test_generative_functions(self, testdir):