Convert NextProtoNegotiationTests to use pytest-style tests (#569)

* Convert NextProtoNegotiationTests to use pytest-style tests

Addresses #340.

* Fix Twisted test suite

See https://twistedmatrix.com/trac/ticket/8876

* Remove tests for OpenSSL with no NPN support

NPN was added in OpenSSL 1.0.1.  As of version 16.1.0, PyOpenSSL
only supports OpenSSL 1.0.1 or later, so this test is:

1. Testing a use case that's no longer supported.
2. Dead code in CI.

2 files changed, 128 insertions, 152 deletions

diff --git a/tests/test_ssl.py b/tests/test_ssl.py
index 332f5bc..62bbbf7 100644
--- a/tests/test_ssl.py
+++ b/tests/test_ssl.py
@@ -1684,198 +1684,174 @@ class TestServerNameCallback(object):
         assert args == [(server, b"foo1.example.com")]
 
 
-class NextProtoNegotiationTests(TestCase, _LoopbackMixin):
+class TestNextProtoNegotiation(object):
     """
     Test for Next Protocol Negotiation in PyOpenSSL.
     """
-    if _lib.Cryptography_HAS_NEXTPROTONEG:
-        def test_npn_success(self):
-            """
-            Tests that clients and servers that agree on the negotiated next
-            protocol can correct establish a connection, and that the agreed
-            protocol is reported by the connections.
-            """
-            advertise_args = []
-            select_args = []
-
-            def advertise(conn):
-                advertise_args.append((conn,))
-                return [b'http/1.1', b'spdy/2']
-
-            def select(conn, options):
-                select_args.append((conn, options))
-                return b'spdy/2'
+    def test_npn_success(self):
+        """
+        Tests that clients and servers that agree on the negotiated next
+        protocol can correct establish a connection, and that the agreed
+        protocol is reported by the connections.
+        """
+        advertise_args = []
+        select_args = []
 
-            server_context = Context(TLSv1_METHOD)
-            server_context.set_npn_advertise_callback(advertise)
+        def advertise(conn):
+            advertise_args.append((conn,))
+            return [b'http/1.1', b'spdy/2']
 
-            client_context = Context(TLSv1_METHOD)
-            client_context.set_npn_select_callback(select)
+        def select(conn, options):
+            select_args.append((conn, options))
+            return b'spdy/2'
 
-            # Necessary to actually accept the connection
-            server_context.use_privatekey(
-                load_privatekey(FILETYPE_PEM, server_key_pem))
-            server_context.use_certificate(
-                load_certificate(FILETYPE_PEM, server_cert_pem))
+        server_context = Context(TLSv1_METHOD)
+        server_context.set_npn_advertise_callback(advertise)
 
-            # Do a little connection to trigger the logic
-            server = Connection(server_context, None)
-            server.set_accept_state()
+        client_context = Context(TLSv1_METHOD)
+        client_context.set_npn_select_callback(select)
 
-            client = Connection(client_context, None)
-            client.set_connect_state()
+        # Necessary to actually accept the connection
+        server_context.use_privatekey(
+            load_privatekey(FILETYPE_PEM, server_key_pem))
+        server_context.use_certificate(
+            load_certificate(FILETYPE_PEM, server_cert_pem))
 
-            self._interactInMemory(server, client)
+        # Do a little connection to trigger the logic
+        server = Connection(server_context, None)
+        server.set_accept_state()
 
-            self.assertEqual([(server,)], advertise_args)
-            self.assertEqual([(client, [b'http/1.1', b'spdy/2'])], select_args)
+        client = Connection(client_context, None)
+        client.set_connect_state()
 
-            self.assertEqual(server.get_next_proto_negotiated(), b'spdy/2')
-            self.assertEqual(client.get_next_proto_negotiated(), b'spdy/2')
+        interact_in_memory(server, client)
 
-        def test_npn_client_fail(self):
-            """
-            Tests that when clients and servers cannot agree on what protocol
-            to use next that the TLS connection does not get established.
-            """
-            advertise_args = []
-            select_args = []
+        assert advertise_args == [(server,)]
+        assert select_args == [(client, [b'http/1.1', b'spdy/2'])]
 
-            def advertise(conn):
-                advertise_args.append((conn,))
-                return [b'http/1.1', b'spdy/2']
+        assert server.get_next_proto_negotiated() == b'spdy/2'
+        assert client.get_next_proto_negotiated() == b'spdy/2'
 
-            def select(conn, options):
-                select_args.append((conn, options))
-                return b''
+    def test_npn_client_fail(self):
+        """
+        Tests that when clients and servers cannot agree on what protocol
+        to use next that the TLS connection does not get established.
+        """
+        advertise_args = []
+        select_args = []
 
-            server_context = Context(TLSv1_METHOD)
-            server_context.set_npn_advertise_callback(advertise)
+        def advertise(conn):
+            advertise_args.append((conn,))
+            return [b'http/1.1', b'spdy/2']
 
-            client_context = Context(TLSv1_METHOD)
-            client_context.set_npn_select_callback(select)
+        def select(conn, options):
+            select_args.append((conn, options))
+            return b''
 
-            # Necessary to actually accept the connection
-            server_context.use_privatekey(
-                load_privatekey(FILETYPE_PEM, server_key_pem))
-            server_context.use_certificate(
-                load_certificate(FILETYPE_PEM, server_cert_pem))
+        server_context = Context(TLSv1_METHOD)
+        server_context.set_npn_advertise_callback(advertise)
 
-            # Do a little connection to trigger the logic
-            server = Connection(server_context, None)
-            server.set_accept_state()
+        client_context = Context(TLSv1_METHOD)
+        client_context.set_npn_select_callback(select)
 
-            client = Connection(client_context, None)
-            client.set_connect_state()
+        # Necessary to actually accept the connection
+        server_context.use_privatekey(
+            load_privatekey(FILETYPE_PEM, server_key_pem))
+        server_context.use_certificate(
+            load_certificate(FILETYPE_PEM, server_cert_pem))
 
-            # If the client doesn't return anything, the connection will fail.
-            self.assertRaises(Error, self._interactInMemory, server, client)
+        # Do a little connection to trigger the logic
+        server = Connection(server_context, None)
+        server.set_accept_state()
 
-            self.assertEqual([(server,)], advertise_args)
-            self.assertEqual([(client, [b'http/1.1', b'spdy/2'])], select_args)
+        client = Connection(client_context, None)
+        client.set_connect_state()
 
-        def test_npn_select_error(self):
-            """
-            Test that we can handle exceptions in the select callback. If
-            select fails it should be fatal to the connection.
-            """
-            advertise_args = []
+        # If the client doesn't return anything, the connection will fail.
+        with pytest.raises(Error):
+            interact_in_memory(server, client)
 
-            def advertise(conn):
-                advertise_args.append((conn,))
-                return [b'http/1.1', b'spdy/2']
+        assert advertise_args == [(server,)]
+        assert select_args == [(client, [b'http/1.1', b'spdy/2'])]
 
-            def select(conn, options):
-                raise TypeError
+    def test_npn_select_error(self):
+        """
+        Test that we can handle exceptions in the select callback. If
+        select fails it should be fatal to the connection.
+        """
+        advertise_args = []
 
-            server_context = Context(TLSv1_METHOD)
-            server_context.set_npn_advertise_callback(advertise)
+        def advertise(conn):
+            advertise_args.append((conn,))
+            return [b'http/1.1', b'spdy/2']
 
-            client_context = Context(TLSv1_METHOD)
-            client_context.set_npn_select_callback(select)
+        def select(conn, options):
+            raise TypeError
 
-            # Necessary to actually accept the connection
-            server_context.use_privatekey(
-                load_privatekey(FILETYPE_PEM, server_key_pem))
-            server_context.use_certificate(
-                load_certificate(FILETYPE_PEM, server_cert_pem))
+        server_context = Context(TLSv1_METHOD)
+        server_context.set_npn_advertise_callback(advertise)
 
-            # Do a little connection to trigger the logic
-            server = Connection(server_context, None)
-            server.set_accept_state()
+        client_context = Context(TLSv1_METHOD)
+        client_context.set_npn_select_callback(select)
 
-            client = Connection(client_context, None)
-            client.set_connect_state()
+        # Necessary to actually accept the connection
+        server_context.use_privatekey(
+            load_privatekey(FILETYPE_PEM, server_key_pem))
+        server_context.use_certificate(
+            load_certificate(FILETYPE_PEM, server_cert_pem))
 
-            # If the callback throws an exception it should be raised here.
-            self.assertRaises(
-                TypeError, self._interactInMemory, server, client
-            )
-            self.assertEqual([(server,)], advertise_args)
+        # Do a little connection to trigger the logic
+        server = Connection(server_context, None)
+        server.set_accept_state()
 
-        def test_npn_advertise_error(self):
-            """
-            Test that we can handle exceptions in the advertise callback. If
-            advertise fails no NPN is advertised to the client.
-            """
-            select_args = []
+        client = Connection(client_context, None)
+        client.set_connect_state()
 
-            def advertise(conn):
-                raise TypeError
+        # If the callback throws an exception it should be raised here.
+        with pytest.raises(TypeError):
+            interact_in_memory(server, client)
+        assert advertise_args == [(server,), ]
 
-            def select(conn, options):  # pragma: nocover
-                """
-                Assert later that no args are actually appended.
-                """
-                select_args.append((conn, options))
-                return b''
+    def test_npn_advertise_error(self):
+        """
+        Test that we can handle exceptions in the advertise callback. If
+        advertise fails no NPN is advertised to the client.
+        """
+        select_args = []
 
-            server_context = Context(TLSv1_METHOD)
-            server_context.set_npn_advertise_callback(advertise)
+        def advertise(conn):
+            raise TypeError
 
-            client_context = Context(TLSv1_METHOD)
-            client_context.set_npn_select_callback(select)
+        def select(conn, options):  # pragma: nocover
+            """
+            Assert later that no args are actually appended.
+            """
+            select_args.append((conn, options))
+            return b''
 
-            # Necessary to actually accept the connection
-            server_context.use_privatekey(
-                load_privatekey(FILETYPE_PEM, server_key_pem))
-            server_context.use_certificate(
-                load_certificate(FILETYPE_PEM, server_cert_pem))
+        server_context = Context(TLSv1_METHOD)
+        server_context.set_npn_advertise_callback(advertise)
 
-            # Do a little connection to trigger the logic
-            server = Connection(server_context, None)
-            server.set_accept_state()
+        client_context = Context(TLSv1_METHOD)
+        client_context.set_npn_select_callback(select)
 
-            client = Connection(client_context, None)
-            client.set_connect_state()
+        # Necessary to actually accept the connection
+        server_context.use_privatekey(
+            load_privatekey(FILETYPE_PEM, server_key_pem))
+        server_context.use_certificate(
+            load_certificate(FILETYPE_PEM, server_cert_pem))
 
-            # If the client doesn't return anything, the connection will fail.
-            self.assertRaises(
-                TypeError, self._interactInMemory, server, client
-            )
-            self.assertEqual([], select_args)
+        # Do a little connection to trigger the logic
+        server = Connection(server_context, None)
+        server.set_accept_state()
 
-    else:
-        # No NPN.
-        def test_npn_not_implemented(self):
-            # Test the context methods first.
-            context = Context(TLSv1_METHOD)
-            fail_methods = [
-                context.set_npn_advertise_callback,
-                context.set_npn_select_callback,
-            ]
-            for method in fail_methods:
-                self.assertRaises(
-                    NotImplementedError, method, None
-                )
+        client = Connection(client_context, None)
+        client.set_connect_state()
 
-            # Now test a connection.
-            conn = Connection(context)
-            fail_methods = [
-                conn.get_next_proto_negotiated,
-            ]
-            for method in fail_methods:
-                self.assertRaises(NotImplementedError, method)
+        # If the client doesn't return anything, the connection will fail.
+        with pytest.raises(TypeError):
+            interact_in_memory(server, client)
+        assert select_args == []
 
 
 class ApplicationLayerProtoNegotiationTests(TestCase, _LoopbackMixin):
diff --git a/tox.ini b/tox.ini
index 9a41630..964b88c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -29,7 +29,7 @@ passenv = ARCHFLAGS CFLAGS LC_ALL LDFLAGS PATH LD_LIBRARY_PATH TERM
 commands =
     python -c "import OpenSSL.SSL; print(OpenSSL.SSL.SSLeay_version(OpenSSL.SSL.SSLEAY_VERSION))"
     python -c "import cryptography; print(cryptography.__version__)"
-    trial --reporter=text twisted
+    python -m twisted.trial
 
 [testenv:py35-urllib3Master]
 basepython=python3.5