Add HallucinationGuardrail no-op implementation with tests (#2869)

- Add `HallucinationGuardrail` class as enterprise feature placeholder
- Update LLM guardrail events to support `HallucinationGuardrail` instances
- Add comprehensive tests for `HallucinationGuardrail` initialization and behavior
- Add integration tests for `HallucinationGuardrail` with task execution system
- Ensure no-op behavior always returns True

tests/test_hallucination_guardrail.py

@@ -0,0 +1,108 @@
+from unittest.mock import Mock
+
+import pytest
+
+from crewai.llm import LLM
+from crewai.tasks.hallucination_guardrail import HallucinationGuardrail
+from crewai.tasks.task_output import TaskOutput
+
+
+def test_hallucination_guardrail_initialization():
+    """Test that the hallucination guardrail initializes correctly with all parameters."""
+    mock_llm = Mock(spec=LLM)
+
+    guardrail = HallucinationGuardrail(context="Test reference context", llm=mock_llm)
+
+    assert guardrail.context == "Test reference context"
+    assert guardrail.llm == mock_llm
+    assert guardrail.threshold is None
+    assert guardrail.tool_response == ""
+
+    guardrail = HallucinationGuardrail(
+        context="Test reference context",
+        llm=mock_llm,
+        threshold=8.5,
+        tool_response="Sample tool response",
+    )
+
+    assert guardrail.context == "Test reference context"
+    assert guardrail.llm == mock_llm
+    assert guardrail.threshold == 8.5
+    assert guardrail.tool_response == "Sample tool response"
+
+
+def test_hallucination_guardrail_no_op_behavior():
+    """Test that the guardrail always returns True in the open-source version."""
+    mock_llm = Mock(spec=LLM)
+    guardrail = HallucinationGuardrail(
+        context="Test reference context",
+        llm=mock_llm,
+        threshold=9.0,
+    )
+
+    task_output = TaskOutput(
+        raw="Sample task output",
+        description="Test task",
+        expected_output="Expected output",
+        agent="Test Agent",
+    )
+
+    result, output = guardrail(task_output)
+
+    assert result is True
+    assert output == "Sample task output"
+
+
+def test_hallucination_guardrail_description():
+    """Test that the guardrail provides the correct description for event logging."""
+    guardrail = HallucinationGuardrail(
+        context="Test reference context", llm=Mock(spec=LLM)
+    )
+
+    assert guardrail.description == "HallucinationGuardrail (no-op)"
+
+
+@pytest.mark.parametrize(
+    "context,task_output_text,threshold,tool_response",
+    [
+        (
+            "Earth orbits the Sun once every 365.25 days.",
+            "It takes Earth approximately one year to go around the Sun.",
+            None,
+            "",
+        ),
+        (
+            "Python was created by Guido van Rossum in 1991.",
+            "Python is a programming language developed by Guido van Rossum.",
+            7.5,
+            "",
+        ),
+        (
+            "The capital of France is Paris.",
+            "Paris is the largest city and capital of France.",
+            9.0,
+            "Geographic API returned: France capital is Paris",
+        ),
+    ],
+)
+def test_hallucination_guardrail_always_passes(
+    context, task_output_text, threshold, tool_response
+):
+    """Test that the guardrail always passes regardless of configuration in open-source version."""
+    mock_llm = Mock(spec=LLM)
+
+    guardrail = HallucinationGuardrail(
+        context=context, llm=mock_llm, threshold=threshold, tool_response=tool_response
+    )
+
+    task_output = TaskOutput(
+        raw=task_output_text,
+        description="Test task",
+        expected_output="Expected output",
+        agent="Test Agent",
+    )
+
+    result, output = guardrail(task_output)
+
+    assert result is True
+    assert output == task_output_text

tests/test_task_guardrails.py

@@ -1,9 +1,10 @@
-from unittest.mock import ANY, Mock, patch
+from unittest.mock import Mock, patch
 
 import pytest
 
 from crewai import Agent, Task
 from crewai.llm import LLM
+from crewai.tasks.hallucination_guardrail import HallucinationGuardrail
 from crewai.tasks.llm_guardrail import LLMGuardrail
 from crewai.tasks.task_output import TaskOutput
 from crewai.utilities.events import (
@@ -267,3 +268,37 @@ def test_guardrail_when_an_error_occurs(sample_agent, task_output):
             max_retries=0,
         )
         task.execute_sync(agent=sample_agent)
+
+
+def test_hallucination_guardrail_integration():
+    """Test that HallucinationGuardrail integrates properly with the task system."""
+    agent = Mock()
+    agent.role = "test_agent"
+    agent.execute_task.return_value = "test result"
+    agent.crew = None
+
+    mock_llm = Mock(spec=LLM)
+    guardrail = HallucinationGuardrail(
+        context="Test reference context for validation", llm=mock_llm, threshold=8.0
+    )
+
+    task = Task(
+        description="Test task with hallucination guardrail",
+        expected_output="Valid output",
+        guardrail=guardrail,
+    )
+
+    result = task.execute_sync(agent=agent)
+    assert isinstance(result, TaskOutput)
+    assert result.raw == "test result"
+
+
+def test_hallucination_guardrail_description_in_events():
+    """Test that HallucinationGuardrail description appears correctly in events."""
+    mock_llm = Mock(spec=LLM)
+    guardrail = HallucinationGuardrail(context="Test context", llm=mock_llm)
+
+    assert guardrail.description == "HallucinationGuardrail (no-op)"
+
+    event = LLMGuardrailStartedEvent(guardrail=guardrail, retry_count=0)
+    assert event.guardrail == "HallucinationGuardrail (no-op)"