Fix issue #2402: Handle missing templates gracefully

Co-Authored-By: Joe Moura <joao@crewai.com>

tests/test_templates.py

@@ -0,0 +1,47 @@
+"""Test template handling in Agent creation."""
+
+import pytest
+from crewai import Agent, Task, Crew
+
+
+def test_agent_with_only_system_template():
+    """Test that an agent with only system_template works without errors."""
+    agent = Agent(
+        role="Test Role",
+        goal="Test Goal",
+        backstory="Test Backstory",
+        allow_delegation=False,
+        system_template="You are a test agent...",
+        # prompt_template is intentionally missing
+    )
+    
+    task = Task(description="Test task", agent=agent, expected_output="Test output")
+    
+    # This should not raise an error
+    try:
+        agent.execute_task(task)
+        assert True
+    except AttributeError:
+        pytest.fail("AttributeError was raised with only system_template")
+
+
+def test_agent_with_missing_response_template():
+    """Test that an agent with system_template and prompt_template but no response_template works without errors."""
+    agent = Agent(
+        role="Test Role",
+        goal="Test Goal",
+        backstory="Test Backstory",
+        allow_delegation=False,
+        system_template="You are a test agent...",
+        prompt_template="This is a test prompt...",
+        # response_template is intentionally missing
+    )
+    
+    task = Task(description="Test task", agent=agent, expected_output="Test output")
+    
+    # This should not raise an error
+    try:
+        agent.execute_task(task)
+        assert True
+    except AttributeError:
+        pytest.fail("AttributeError was raised with missing response_template")