py36+ tests are definition ordered

changelog/5196.feature.rst

@@ -0,0 +1 @@
+Tests are now ordered by definition order in more cases.

src/_pytest/python.py

@@ -442,11 +442,6 @@ def collect(self) -> Iterable[Union[nodes.Item, nodes.Collector]]:
                 else:
                     values.append(res)
 
-        def sort_key(item):
-            fspath, lineno, _ = item.reportinfo()
-            return (str(fspath), lineno)
-
-        values.sort(key=sort_key)
         return values
 
     def _genfunctions(self, name: str, funcobj) -> Iterator["Function"]:

testing/python/collect.py

@@ -752,6 +752,30 @@ def test_a(y):
         assert len(colitems) == 2
         assert [item.name for item in colitems] == ["test_b", "test_a"]
 
+    def test_ordered_by_definition_order(self, testdir):
+        testdir.makepyfile(
+            """\
+            class Test1:
+                def test_foo(): pass
+                def test_bar(): pass
+            class Test2:
+                def test_foo(): pass
+                test_bar = Test1.test_bar
+            """
+        )
+        result = testdir.runpytest("--collect-only")
+        result.stdout.fnmatch_lines(
+            [
+                "*Class Test1*",
+                "*Function test_foo*",
+                "*Function test_bar*",
+                "*Class Test2*",
+                # previously the order was flipped due to Test1.test_bar reference
+                "*Function test_foo*",
+                "*Function test_bar*",
+            ]
+        )
+
 
 class TestConftestCustomization:
     def test_pytest_pycollect_module(self, testdir):

testing/test_collection.py

@@ -677,15 +677,15 @@ def testmethod_two(self, arg0):
         assert len(items) == 4
         assert items[0].name == "testone"
         assert items[1].name == "testmethod_one"
-        assert items[2].name == "testmethod_one"
-        assert items[3].name == "testmethod_two[.[]"
+        assert items[2].name == "testmethod_two[.[]"
+        assert items[3].name == "testmethod_one"
 
         # let's also test getmodpath here
         assert items[0].getmodpath() == "testone"
         assert items[1].getmodpath() == "TestX.testmethod_one"
-        assert items[2].getmodpath() == "TestY.testmethod_one"
         # PR #6202: Fix incorrect result of getmodpath method. (Resolves issue #6189)
-        assert items[3].getmodpath() == "TestY.testmethod_two[.[]"
+        assert items[2].getmodpath() == "TestY.testmethod_two[.[]"
+        assert items[3].getmodpath() == "TestY.testmethod_one"
 
         s = items[0].getmodpath(stopatmodule=False)
         assert s.endswith("test_example_items1.testone")