diff --git a/tests/test_client_init.py b/tests/test_client_init.py
new file mode 100644
index 0000000..f14aebc
--- /dev/null
+++ b/tests/test_client_init.py
@@ -0,0 +1,36 @@
+"""Tests for CueAPI client initialization and error handling."""
+
+import pytest
+
+from cueapi import CueAPI
+from cueapi.exceptions import AuthenticationError
+
+
+class TestClientInit:
+    def test_client_has_cues_resource(self):
+        """Client should have a cues attribute."""
+        client = CueAPI("test-key", base_url="https://example.com")
+        assert hasattr(client, "cues")
+        assert hasattr(client, "executions")
+        client.close()
+
+    def test_client_accepts_base_url(self):
+        """Client should accept a custom base_url."""
+        client = CueAPI("test-key", base_url="https://custom.example.com")
+        assert client._base_url == "https://custom.example.com"
+        client.close()
+
+    def test_client_close_is_idempotent(self):
+        """Calling close() multiple times should not raise."""
+        client = CueAPI("test-key", base_url="https://example.com")
+        client.close()
+        client.close()  # Should not raise
+
+
+class TestClientErrors:
+    def test_invalid_api_key_raises_auth_error(self):
+        """Using an invalid API key should raise AuthenticationError."""
+        client = CueAPI("invalid-key-that-does-not-exist", base_url="https://api-staging-e962.up.railway.app")
+        with pytest.raises((AuthenticationError, Exception)):
+            client.cues.list()
+        client.close()