Move inheritance tests into the proper file

tests/test_callbacks.py

 import pytest
 
 
-def test_inheritance(msg):
-    from pybind11_tests import Pet, Dog, Rabbit, dog_bark, pet_name_species
-
-    roger = Rabbit('Rabbit')
-    assert roger.name() + " is a " + roger.species() == "Rabbit is a parrot"
-    assert pet_name_species(roger) == "Rabbit is a parrot"
-
-    polly = Pet('Polly', 'parrot')
-    assert polly.name() + " is a " + polly.species() == "Polly is a parrot"
-    assert pet_name_species(polly) == "Polly is a parrot"
-
-    molly = Dog('Molly')
-    assert molly.name() + " is a " + molly.species() == "Molly is a dog"
-    assert pet_name_species(molly) == "Molly is a dog"
-
-    assert dog_bark(molly) == "Woof!"
-
-    with pytest.raises(TypeError) as excinfo:
-        dog_bark(polly)
-    assert msg(excinfo.value) == """
-        Incompatible function arguments. The following argument types are supported:
-            1. (arg0: m.Dog) -> str
-            Invoked with: <m.Pet object at 0>
-    """
-
-
 def test_callbacks():
     from functools import partial
     from pybind11_tests import (test_callback1, test_callback2, test_callback3,

tests/test_inheritance.py

+import pytest
+
+
+def test_inheritance(msg):
+    from pybind11_tests import Pet, Dog, Rabbit, dog_bark, pet_name_species
+
+    roger = Rabbit('Rabbit')
+    assert roger.name() + " is a " + roger.species() == "Rabbit is a parrot"
+    assert pet_name_species(roger) == "Rabbit is a parrot"
+
+    polly = Pet('Polly', 'parrot')
+    assert polly.name() + " is a " + polly.species() == "Polly is a parrot"
+    assert pet_name_species(polly) == "Polly is a parrot"
+
+    molly = Dog('Molly')
+    assert molly.name() + " is a " + molly.species() == "Molly is a dog"
+    assert pet_name_species(molly) == "Molly is a dog"
+
+    assert dog_bark(molly) == "Woof!"
+
+    with pytest.raises(TypeError) as excinfo:
+        dog_bark(polly)
+    assert msg(excinfo.value) == """
+        Incompatible function arguments. The following argument types are supported:
+            1. (arg0: m.Dog) -> str
+            Invoked with: <m.Pet object at 0>
+    """
 
 
 def test_automatic_upcasting():