Refactor test_basic.py to use public APIs. (#936)

* refactor: Move `CreateTypeLib` import to top-level in `test_basic.py`.

Relocate `CreateTypeLib` from `BasicTest.test_guid` to the top level of
`test/test_basic.py` to follow project conventions.

* refactor: Use `SYS_WIN32` constant in `test_basic.py`.

Replace magic number `1` with `SYS_WIN32` in `_CreateTypeLib2` calls.

* refactor: Use public `CreateTypeLib` in `test_basic.py`.

Replace internal `_CreateTypeLib2` calls with public `CreateTypeLib`.

The primary goal of these tests is to verify the basic mechanics of COM
pointers, such as reference counting and `QueryInterface` behavior, which are
common to all COM interfaces.
Testing low-level, private functions like `_CreateTypeLib2` is not the
objective here.

* refactor: Remove redundant `IUnknown` import in `test_basic.py`.

Remove the redundant inline import of `IUnknown` from the `test_IUnknown`
method, as it is already imported at the top level of `test/test_basic.py`.

* refactor: Remove commented-out code in `test_basic.py`.

Remove a redundant commented-out `import` statement from the top of
`test/test_basic.py`.

* test: Verify `IUnknown` instance in `test_basic.py`.

Add assertions to `BasicTest.test_refcounts` and `BasicTest.test_qi` to verify
that the object returned by `CreateTypeLib` is an instance of `IUnknown`.

Author: junkmd

comtypes/test/test_basic.py

@@ -1,9 +1,8 @@
-##import ut
 import unittest as ut
-from ctypes import HRESULT, POINTER, byref
+from ctypes import HRESULT, POINTER
 
 from comtypes import GUID, STDMETHOD, IUnknown
-from comtypes.typeinfo import ICreateTypeLib2, _CreateTypeLib2
+from comtypes.typeinfo import SYS_WIN32, CreateTypeLib, ICreateTypeLib2
 
 # XXX leaks references!
 
@@ -14,8 +13,6 @@ def method_count(interface):
 
 class BasicTest(ut.TestCase):
     def test_IUnknown(self):
-        from comtypes import IUnknown
-
         self.assertEqual(method_count(IUnknown), 3)
 
     def test_release(self):
@@ -24,8 +21,9 @@ def test_release(self):
     def test_refcounts(self):
         # Since all COM interfaces derive from IUnknown and have the same reference counting behavior, any interface
         # — whether ICreateTypeLib2 or otherwise — could be used for this test.
-        p = POINTER(ICreateTypeLib2)()
-        _CreateTypeLib2(1, "blabla", byref(p))
+        p = CreateTypeLib("blabla", syskind=SYS_WIN32)
+        self.assertIsInstance(p, ICreateTypeLib2)
+        self.assertIsInstance(p, IUnknown)
         # initial refcount is 2
         for i in range(2, 10):
             self.assertEqual(p.AddRef(), i)
@@ -35,8 +33,9 @@ def test_refcounts(self):
     def test_qi(self):
         # Since all COM interfaces derive from IUnknown and have the same QueryInterface behavior, any interface
         # — whether ICreateTypeLib2 or otherwise — could be used for this test.
-        p = POINTER(ICreateTypeLib2)()
-        _CreateTypeLib2(1, "blabla", byref(p))
+        p = CreateTypeLib("blabla", syskind=SYS_WIN32)
+        self.assertIsInstance(p, ICreateTypeLib2)
+        self.assertIsInstance(p, IUnknown)
         self.assertEqual(p.AddRef(), 2)
         self.assertEqual(p.Release(), 1)
 
@@ -115,8 +114,6 @@ def test_identity(self):
         self.assertEqual(a, b)
         self.assertEqual(hash(a), hash(b))
 
-        from comtypes.typeinfo import CreateTypeLib
-
         # we do not save the lib, so no file will be created.
         # these should NOT be identical
         a = CreateTypeLib("blahblah")