Add is_gossipsub fixture in interop test

To use the same code to test against both routers: floodsub and
gossipsub.

tests/pubsub/conftest.py

@@ -0,0 +1,43 @@
+import pytest
+
+from tests.factories import FloodsubFactory, GossipsubFactory, PubsubFactory
+
+from .configs import GOSSIPSUB_PARAMS
+
+
+def _make_pubsubs(hosts, pubsub_routers, cache_size):
+    if len(pubsub_routers) != len(hosts):
+        raise ValueError(
+            f"lenght of pubsub_routers={pubsub_routers} should be equaled to the "
+            f"length of hosts={len(hosts)}"
+        )
+    return tuple(
+        PubsubFactory(host=host, router=router, cache_size=cache_size)
+        for host, router in zip(hosts, pubsub_routers)
+    )
+
+
+@pytest.fixture
+def pubsub_cache_size():
+    return None  # default
+
+
+@pytest.fixture
+def gossipsub_params():
+    return GOSSIPSUB_PARAMS
+
+
+@pytest.fixture
+def pubsubs_fsub(num_hosts, hosts, pubsub_cache_size):
+    floodsubs = FloodsubFactory.create_batch(num_hosts)
+    _pubsubs_fsub = _make_pubsubs(hosts, floodsubs, pubsub_cache_size)
+    yield _pubsubs_fsub
+    # TODO: Clean up
+
+
+@pytest.fixture
+def pubsubs_gsub(num_hosts, hosts, pubsub_cache_size, gossipsub_params):
+    gossipsubs = GossipsubFactory.create_batch(num_hosts, **gossipsub_params._asdict())
+    _pubsubs_gsub = _make_pubsubs(hosts, gossipsubs, pubsub_cache_size)
+    yield _pubsubs_gsub
+    # TODO: Clean up