Add test that C extension is correctly loaded

tests/test_quoting.py

@@ -2,6 +2,7 @@
 from hypothesis import assume, example, given, note
 from hypothesis import strategies as st
 
+import yarl
 from yarl._quoting import NO_EXTENSIONS
 from yarl._quoting_py import _Quoter as _PyQuoter
 from yarl._quoting_py import _Unquoter as _PyUnquoter
@@ -38,6 +39,11 @@ def unquoter(request):
     unquoter_ids = ["PyUnquoter"]
 
 
+@pytest.mark.skipif(NO_EXTENSIONS, reason="Extensions available but not imported")
+def test_quoting_c_loaded():
+    assert "_quoting_c" in dir(yarl)
+
+
 def hexescape(char):
     """Escape char as RFC 2396 specifies"""
     hex_repr = hex(ord(char))[2:].upper()