1 files changed, 79 insertions, 0 deletions
diff --git a/ext/pybind11/tests/test_alias_initialization.py b/ext/pybind11/tests/test_alias_initialization.py
new file mode 100644
index 000000000..0ed9d2f79
--- /dev/null
+++ b/ext/pybind11/tests/test_alias_initialization.py
@@ -0,0 +1,79 @@
+import gc
+
+
+def test_alias_delay_initialization1(capture):
+    """A only initializes its trampoline class when we inherit from it; if we just
+    create and use an A instance directly, the trampoline initialization is bypassed
+    and we only initialize an A() instead (for performance reasons).
+    """
+    from pybind11_tests import A, call_f
+
+    class B(A):
+        def __init__(self):
+            super(B, self).__init__()
+
+        def f(self):
+            print("In python f()")
+
+    # C++ version
+    with capture:
+        a = A()
+        call_f(a)
+        del a
+        gc.collect()
+    assert capture == "A.f()"
+
+    # Python version
+    with capture:
+        b = B()
+        call_f(b)
+        del b
+        gc.collect()
+    assert capture == """
+        PyA.PyA()
+        PyA.f()
+        In python f()
+        PyA.~PyA()
+    """
+
+
+def test_alias_delay_initialization2(capture):
+    """A2, unlike the above, is configured to always initialize the alias; while
+    the extra initialization and extra class layer has small virtual dispatch
+    performance penalty, it also allows us to do more things with the trampoline
+    class such as defining local variables and performing construction/destruction.
+    """
+    from pybind11_tests import A2, call_f
+
+    class B2(A2):
+        def __init__(self):
+            super(B2, self).__init__()
+
+        def f(self):
+            print("In python B2.f()")
+
+    # No python subclass version
+    with capture:
+        a2 = A2()
+        call_f(a2)
+        del a2
+        gc.collect()
+    assert capture == """
+        PyA2.PyA2()
+        PyA2.f()
+        A2.f()
+        PyA2.~PyA2()
+    """
+
+    # Python subclass version
+    with capture:
+        b2 = B2()
+        call_f(b2)
+        del b2
+        gc.collect()
+    assert capture == """
+        PyA2.PyA2()
+        PyA2.f()
+        In python B2.f()
+        PyA2.~PyA2()
+    """