Rue

Rue is a Python testing framework for AI projects. It follows pytest syntax and culture while introducing components essential for testing AI software: metrics, typed datasets, semantic predicates (LLM-as-a-Judge), and OTEL traces.

Installation

uv add rue

Rue 101

Follow pytest habits...

• Create 'rue_*.py' files
• Write 'def test_*' functions
• Use 'rue.resource' instead of 'pytest.fixture'
• Add 'assert' expressions within the functions
• Run 'uv run rue test'

...while leveraging Rue APIs.

• Use 'with metrics()' context to turn failed assertions into quality metrics
• Use 'has_facts()' and other semantic predicates for asserting natural language
• Access OTEL span data and assert it with 'follows_policy()' predicate
• Parse datasets into clearly typed and validated data objects

Example

import rue
from rue import Case, Metric, metrics
from rue.predicates import has_unsupported_facts, follows_policy

from pydantic import BaseModel

@rue.sut
def store_chatbot(prompt: str) -> str:
    return call_llm(prompt)

@rue.metric
def accuracy():
    metric = Metric()
    yield metric

    assert metric.mean > 0.8
    yield metric.mean

class Refs(BaseModel):
    kb: str
    expected_tool: str | None = None

cases = [
    Case(sut_input_values={"prompt": "When are you open?"}, references=Refs(kb="Store hours: 9 AM - 6 PM, Monday-Saturday. Closed Sundays.")),
    Case(sut_input_values={"prompt": "Return policy?"}, references=Refs(kb="30-day returns with receipt.")),
    Case(sut_input_values={"prompt": "How much for the Nike Air Max?"}, references=Refs(kb="Nike Air Max: $129.99", expected_tool="offer_product")),
]

@rue.iter_cases(cases)
@rue.repeat(3)
async def test_chatbot_no_hallucinations(
    case: Case[Refs],
    store_chatbot,
    accuracy: Metric,
    trace_context):
    """AI agent relies on knowledge base and tool calls for transactional questions"""
    response = store_chatbot(**case.sut_input_values)

    # Verify the answer don't have any unsupported facts
    with metrics(accuracy):
        assert not await has_unsupported_facts(response, case.references.kb)

    # Verify tool was called when expected
    if expected_tool := case.references.expected_tool:
        sut_spans = trace_context.get_sut_spans(name="store_chatbot")
        tool_names = [
            s.attributes.get("llm.request.functions.0.name")
            for s in trace_context.get_llm_calls()
            if s.attributes
        ]
        assert expected_tool in tool_names

Run it:

rue test --trace

Use a custom run UUID when you need stable correlation IDs:

rue test --trace --run-id 3f5f5e9a-1c2d-4b5f-9c2b-7f6d8a9b0c1d

Output:

Rue Test Runner
=================

Collected 1 test

test_example.py::test_chatbot_responds ✓

==================== 1 passed in 0.08s ====================

License

This project is licensed under the MIT License - see the LICENSE file for details.