Apply @vepkenez suggestion, Building MockInfuraClient.

nucypher/blockchain/eth/clients.py

@@ -267,7 +267,7 @@ class GethClient(Web3Client):
 
     @classmethod
     def _get_variant(cls, w3):
-        if 'infura' in w3.provider.endpoint_uri:
+        if 'infura' in getattr(w3.provider, 'endpoint_uri', ''):
             return InfuraClient
         return cls
 
@@ -331,6 +331,7 @@ def unlock_account(self, address, password):
     def sync(self, *args, **kwargs):
         return True
 
+
 class EthereumTesterClient(Web3Client):
 
     is_local = True

tests/blockchain/eth/clients/test_mocked_clients.py

@@ -72,14 +72,17 @@ def attach_middleware(self):
         pass
 
 
+class InfuraTestClient(BlockchainInterfaceTestBase):
+
+    def _attach_provider(self, *args, **kwargs) -> None:
+        super()._attach_provider(provider=MockInfuraProvider())
+
+
 class GethClientTestBlockchain(BlockchainInterfaceTestBase):
 
     def _attach_provider(self, *args, **kwargs) -> None:
         super()._attach_provider(provider=MockGethProvider())
 
-    def _get_infura_provider(self):
-        return MockInfuraProvider()
-
     @property
     def is_local(self):
         return int(self.w3.net.version) not in PUBLIC_CHAINS
@@ -112,9 +115,9 @@ def test_geth_web3_client():
 
 
 def test_infura_web3_client():
-    interface = GethClientTestBlockchain(
-        provider_uri='infura://1234567890987654321abcdef'
-    )
+    interface = InfuraTestClient(provider_uri='infura://1234567890987654321abcdef')
+    interface.connect(fetch_registry=False, sync_now=False)
+
     assert isinstance(interface.client, InfuraClient)
     assert interface.node_technology == 'Geth'
     assert interface.node_version == 'v1.8.23-omnibus-2ad89aaa'