Test describing crash behaviour when tests package is unavailable

tests/test_package.py

@@ -0,0 +1,33 @@
+import builtins
+import pytest
+
+from nucypher.exceptions import DevelopmentInstallationRequired
+
+
+def test_development_install_required(capsys, mocker):
+    real_import = builtins.__import__
+
+    def mock_import(name, *args, **kwargs):
+        if 'tests' in name:
+            raise ImportError
+        return real_import(name, *args, **kwargs)
+
+    # Test lazy imports for entities that depends on the tests package
+    try:
+        builtins.__import__ = mock_import
+
+        # For example...
+        from nucypher.characters.unlawful import Vladimir     # Import OK
+        with pytest.raises(DevelopmentInstallationRequired):  # Lazy Action
+            Vladimir.from_target_ursula(target_ursula=mocker.Mock())
+
+        from nucypher.blockchain.eth.providers import _get_pyevm_test_backend
+        with pytest.raises(DevelopmentInstallationRequired):
+            _get_pyevm_test_backend()
+
+        from nucypher.characters.control.controllers import JSONRPCController
+        with pytest.raises(DevelopmentInstallationRequired):
+            JSONRPCController.test_client(self=mocker.Mock())
+
+    finally:
+        builtins.__import__ = real_import