Add discover_imports in conf, don't collect imported classes named Test* closes #12749`

AUTHORS

@@ -400,6 +400,7 @@ Stefanie Molin
 Stefano Taschini
 Steffen Allner
 Stephan Obermann
+Sven
 Sven-Hendrik Haase
 Sviatoslav Sydorenko
 Sylvain Marié

changelog/12749.feature.rst

@@ -0,0 +1,3 @@
+Add :confval:`discover_imports`, when disabled (default) will make sure to not consider classes which are imported by a test file and starts with Test.
+
+-- by :user:`FreerGit`

src/_pytest/main.py

@@ -78,6 +78,11 @@ def pytest_addoption(parser: Parser) -> None:
         type="args",
         default=[],
     )
+    parser.addini(
+        "discover_imports",
+        "Whether to discover tests in imported modules outside `testpaths`",
+        default=False,
+    )
     group = parser.getgroup("general", "Running and selection options")
     group._addoption(
         "-x",

src/_pytest/python.py

@@ -741,6 +741,12 @@ def newinstance(self):
         return self.obj()
 
     def collect(self) -> Iterable[nodes.Item | nodes.Collector]:
+        if self.config.getini("discover_imports") == ("false" or False):
+            paths = self.config.getini("testpaths")
+            class_file = inspect.getfile(self.obj)
+            if not any(string in class_file for string in paths):
+                return []
+
         if not safe_getattr(self.obj, "__test__", True):
             return []
         if hasinit(self.obj):

testing/test_discover_imports.py

@@ -0,0 +1,100 @@
+from __future__ import annotations
+
+import textwrap
+
+
+def test_discover_imports_enabled(pytester):
+    src_dir = pytester.mkdir("src")
+    tests_dir = pytester.mkdir("tests")
+    pytester.makeini("""
+        [pytest]
+        testpaths = "tests"
+        discover_imports = true
+    """)
+
+    src_file = src_dir / "foo.py"
+
+    src_file.write_text(
+        textwrap.dedent("""\
+    class TestClass(object):
+        def __init__(self):
+            super().__init__()
+
+        def test_foobar(self):
+            return true
+    """),
+        encoding="utf-8",
+    )
+
+    test_file = tests_dir / "foo_test.py"
+    test_file.write_text(
+        textwrap.dedent("""\
+    import sys
+    import os
+
+    current_file = os.path.abspath(__file__)
+    current_dir = os.path.dirname(current_file)
+    parent_dir = os.path.abspath(os.path.join(current_dir, '..'))
+    sys.path.append(parent_dir)
+
+    from src.foo import TestClass
+
+    class TestDomain:
+        def test_testament(self):
+            testament = TestClass()
+            pass
+    """),
+        encoding="utf-8",
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(errors=1)
+
+
+def test_discover_imports_disabled(pytester):
+    src_dir = pytester.mkdir("src")
+    tests_dir = pytester.mkdir("tests")
+    pytester.makeini("""
+        [pytest]
+        testpaths = "tests"
+        discover_imports = false
+    """)
+
+    src_file = src_dir / "foo.py"
+
+    src_file.write_text(
+        textwrap.dedent("""\
+    class Testament(object):
+        def __init__(self):
+            super().__init__()
+            self.collections = ["stamp", "coin"]
+
+        def personal_property(self):
+            return [f"my {x} collection" for x in self.collections]
+    """),
+        encoding="utf-8",
+    )
+
+    test_file = tests_dir / "foo_test.py"
+    test_file.write_text(
+        textwrap.dedent("""\
+    import sys
+    import os
+
+    current_file = os.path.abspath(__file__)
+    current_dir = os.path.dirname(current_file)
+    parent_dir = os.path.abspath(os.path.join(current_dir, '..'))
+    sys.path.append(parent_dir)
+
+    from src.foo import Testament
+
+    class TestDomain:
+        def test_testament(self):
+            testament = Testament()
+            assert testament.personal_property()
+    """),
+        encoding="utf-8",
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=1)