Fixed collection of classes with custom ``__new__`` method

AUTHORS

@@ -35,6 +35,7 @@ David Díaz-Barquero
 David Mohr
 David Vierra
 Diego Russo
+Dmitry Dygalo
 Edison Gustavo Muenz
 Eduardo Schettino
 Elizaveta Shashkova

CHANGELOG.rst

@@ -51,6 +51,10 @@
 * 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
@@ -72,6 +76,7 @@
 .. _@DRMacIver: https://github.com/DRMacIver
 .. _@BeyondEvil: https://github.com/BeyondEvil
 .. _@JonathonSonesen: https://github.com/JonathonSonesen
+.. _@Stranger6667: https://github.com/Stranger6667
 
 
 2.9.2

_pytest/python.py

@@ -662,6 +662,10 @@ class Class(PyCollector):
             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 @@ class Class(PyCollector):
 
 class Instance(PyCollector):
     def _getobj(self):
-        obj = self.parent.obj()
-        return obj
+        return self.parent.obj()
 
     def collect(self):
         self.session._fixturemanager.parsefactories(self)
@@ -793,10 +796,14 @@ class Generator(FunctionMixin, PyCollector):
 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):
     """ fill missing funcargs for a test function. """

testing/python/collect.py

@@ -109,6 +109,18 @@ class TestClass:
         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):