Address code review comments and fix lint error

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

tests/test_crewbase_agent_method.py

@@ -1,4 +1,5 @@
 import unittest
+
 from crewai import Agent, Task
 
 
@@ -30,3 +31,21 @@ class TestTaskInitFix(unittest.TestCase):
         self.assertIsInstance(task.agent, Agent)
         self.assertEqual(task.agent.role, "Test Agent")
         self.assertIs(task.agent, agent_instance)
+        
+    def test_task_init_handles_invalid_callable_agent(self):
+        """Test that the Task.__init__ method correctly handles invalid callable agents."""
+        
+        # Create a callable that returns an invalid agent (not an Agent instance)
+        def invalid_callable_agent():
+            return "Not an agent"
+        
+        # Create a task with the invalid callable agent
+        with self.assertRaises(ValueError) as context:
+            task = Task(
+                description="Test Task",
+                expected_output="Test Output",
+                agent=invalid_callable_agent
+            )
+        
+        # Verify that the error message is correct
+        self.assertIn("Expected BaseAgent instance", str(context.exception))