test: add exception and agents resource test coverage

- 15 tests for all exception classes (defaults, messages, inheritance, hierarchy)
- 3 tests for agents resource (register, me, status)
- Total test count: 12 → 34 (183% increase)

Author: IISweetHeartII

tests/test_agents.py

@@ -0,0 +1,72 @@
+"""Tests for agents resource."""
+
+from unittest.mock import Mock, patch
+
+from agentgram import AgentGram
+
+
+class TestAgentsResource:
+    """Test agents resource methods."""
+
+    @patch("agentgram.http.httpx.Client")
+    def test_register(self, mock_client):
+        """Test agent registration."""
+        mock_response = Mock()
+        mock_response.is_success = True
+        mock_response.json.return_value = {
+            "id": "agent-123",
+            "name": "TestBot",
+            "karma": 0,
+            "created_at": "2026-01-01T00:00:00Z",
+            "updated_at": "2026-01-01T00:00:00Z",
+        }
+        mock_client.return_value.request.return_value = mock_response
+
+        client = AgentGram(api_key="ag_test")
+        agent = client.agents.register(name="TestBot", public_key="abc123")
+
+        assert agent.id == "agent-123"
+        assert agent.name == "TestBot"
+        client.close()
+
+    @patch("agentgram.http.httpx.Client")
+    def test_me(self, mock_client):
+        """Test getting current agent profile."""
+        mock_response = Mock()
+        mock_response.is_success = True
+        mock_response.json.return_value = {
+            "id": "agent-456",
+            "name": "MyAgent",
+            "karma": 100,
+            "created_at": "2026-01-01T00:00:00Z",
+            "updated_at": "2026-01-01T00:00:00Z",
+        }
+        mock_client.return_value.request.return_value = mock_response
+
+        client = AgentGram(api_key="ag_test")
+        me = client.agents.me()
+
+        assert me.id == "agent-456"
+        assert me.name == "MyAgent"
+        assert me.karma == 100
+        client.close()
+
+    @patch("agentgram.http.httpx.Client")
+    def test_status(self, mock_client):
+        """Test getting agent status."""
+        mock_response = Mock()
+        mock_response.is_success = True
+        mock_response.json.return_value = {
+            "online": True,
+            "post_count": 42,
+            "comment_count": 10,
+        }
+        mock_client.return_value.request.return_value = mock_response
+
+        client = AgentGram(api_key="ag_test")
+        status = client.agents.status()
+
+        assert status.online is True
+        assert status.post_count == 42
+        assert status.comment_count == 10
+        client.close()

tests/test_exceptions.py

@@ -0,0 +1,103 @@
+"""Tests for AgentGram exception classes."""
+
+import pytest
+
+from agentgram.exceptions import (
+    AgentGramError,
+    AuthenticationError,
+    RateLimitError,
+    NotFoundError,
+    ValidationError,
+    ServerError,
+)
+
+
+class TestAgentGramError:
+    """Test base error class."""
+
+    def test_message(self):
+        error = AgentGramError("something went wrong")
+        assert str(error) == "something went wrong"
+        assert error.message == "something went wrong"
+
+    def test_status_code_default(self):
+        error = AgentGramError("test")
+        assert error.status_code is None
+
+    def test_status_code_custom(self):
+        error = AgentGramError("test", status_code=418)
+        assert error.status_code == 418
+
+    def test_is_exception(self):
+        error = AgentGramError("test")
+        assert isinstance(error, Exception)
+
+
+class TestAuthenticationError:
+    def test_defaults(self):
+        error = AuthenticationError()
+        assert error.status_code == 401
+        assert "Invalid or missing API key" in str(error)
+
+    def test_custom_message(self):
+        error = AuthenticationError("Token expired")
+        assert str(error) == "Token expired"
+        assert error.status_code == 401
+
+    def test_inheritance(self):
+        error = AuthenticationError()
+        assert isinstance(error, AgentGramError)
+
+
+class TestRateLimitError:
+    def test_defaults(self):
+        error = RateLimitError()
+        assert error.status_code == 429
+        assert "Rate limit" in str(error)
+
+    def test_inheritance(self):
+        assert isinstance(RateLimitError(), AgentGramError)
+
+
+class TestNotFoundError:
+    def test_defaults(self):
+        error = NotFoundError()
+        assert error.status_code == 404
+        assert "not found" in str(error).lower()
+
+    def test_inheritance(self):
+        assert isinstance(NotFoundError(), AgentGramError)
+
+
+class TestValidationError:
+    def test_defaults(self):
+        error = ValidationError()
+        assert error.status_code == 400
+
+    def test_inheritance(self):
+        assert isinstance(ValidationError(), AgentGramError)
+
+
+class TestServerError:
+    def test_defaults(self):
+        error = ServerError()
+        assert error.status_code == 500
+
+    def test_inheritance(self):
+        assert isinstance(ServerError(), AgentGramError)
+
+
+class TestErrorHierarchy:
+    """Test that all errors can be caught with base class."""
+
+    def test_catch_all_with_base(self):
+        errors = [
+            AuthenticationError(),
+            RateLimitError(),
+            NotFoundError(),
+            ValidationError(),
+            ServerError(),
+        ]
+        for error in errors:
+            with pytest.raises(AgentGramError):
+                raise error