vigil-eval 0.2.3

The testing framework for AI agents. Fast, framework-agnostic, CI-ready.

Quick Start · Features · Assertions · LLM-as-Judge · CI Integration · PyPI

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Why Vigil?

40% of agentic AI projects risk cancellation due to reliability issues. Only 52% of teams run any form of evaluation. The rest ship and pray.

Existing tools are either framework-specific, complex to set up, or disconnected from CI/CD. There's no "pytest for AI."

Vigil changes that. Write AI tests in plain Python. Run them in CI. Catch regressions before production.

pip install vigil-eval

Quick Start

from vigil import test, FunctionAgent, assert_contains, assert_cost_under

agent = FunctionAgent(my_chatbot)

@test()
def test_greeting():
    result = agent.run("Hello!")
    assert_contains(result, "hello")
    assert_cost_under(result, 0.01)

vigil run

That's it. No config files, no setup, no boilerplate.

Features

Feature	Description
11+ assertions	Content, cost, latency, semantic, hallucination, LLM-as-judge
3 agent types	Python functions, HTTP APIs, CLI tools
LLM-as-judge	Use GPT/Claude to grade your agent's output against criteria
Snapshot testing	Save golden outputs, detect regressions automatically
Cost tracking	Auto-calculate API costs for 20+ models across 4 providers
Plugin system	Extend with custom assertions, agents, and reporters
CI-ready	Exit codes, JSON/HTML reports, GitHub Action included
Parallel execution	Run tests concurrently with --parallel
Async support	Test async agents natively
Zero config	Works out of the box, configure when you need to
Built on pytest	Use everything you already know

Assertions

from vigil import (
    assert_contains,          # output contains expected text
    assert_not_contains,      # output does not contain text
    assert_json_valid,        # output is valid JSON
    assert_matches_regex,     # output matches regex pattern
    assert_cost_under,        # API cost below threshold
    assert_tokens_under,      # token usage below limit
    assert_latency_under,     # response time below threshold
    assert_semantic_match,    # semantically similar to reference
    assert_no_hallucination,  # output grounded in provided context
    assert_quality,           # LLM grades output against criteria
    assert_rubric,            # LLM grades against multiple criteria
)

LLM-as-Judge

The most powerful feature in Vigil. Instead of pattern matching, an LLM evaluates your agent's output:

from vigil import test, FunctionAgent, assert_quality, assert_rubric

agent = FunctionAgent(my_agent)

@test()
def test_explanation():
    result = agent.run("Explain quantum computing to a 5-year-old")
    assert_quality(
        result,
        criteria="age-appropriate, accurate, under 100 words, uses simple analogies",
        threshold=0.7,
    )

@test()
def test_article():
    result = agent.run("Write about climate change")
    assert_rubric(
        result,
        rubric={
            "accuracy": "All claims are factually correct",
            "clarity": "Easy to understand, no jargon",
            "completeness": "Covers causes, effects, and solutions",
        },
        threshold=0.7,
    )

Works with OpenAI and Anthropic. Auto-detects your API key.

Agent Types

from vigil import FunctionAgent, HTTPAgent, CLIAgent

# Test a Python function (sync or async)
agent = FunctionAgent(my_function)

# Test an HTTP endpoint
agent = HTTPAgent("http://localhost:8000/chat")

# Test a CLI tool
agent = CLIAgent("python my_agent.py")

Cost Tracking

Vigil auto-calculates API costs for 20+ models:

from vigil import FunctionAgent, assert_cost_under
from vigil.cost import enrich_result

def my_agent(msg):
    return {"output": "Hello!", "model": "gpt-4o-mini", "tokens_input": 50, "tokens_output": 100}

result = FunctionAgent(my_agent).run("Hi")
enrich_result(result)
print(result.cost)  # Auto-calculated from pricing table

assert_cost_under(result, 0.01)

Supports OpenAI, Anthropic, Google, and DeepSeek models.

Snapshot Testing

Save golden outputs and detect when your agent's behavior drifts:

from vigil import test, FunctionAgent
from vigil.snapshots import snapshot

@test()
def test_output_stable():
    result = FunctionAgent(my_agent).run("Summarize this document")
    snapshot(result, name="summary_output")

# First run: saves snapshot. Next runs: compares against it.
vigil run

# Accept new outputs when they intentionally change
vigil snapshot update

CI Integration

GitHub Actions

name: AI Tests
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: "3.12"
      - run: pip install vigil-eval
      - run: vigil run
        env:
          OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}

Reports

vigil run --report json > results.json   # For pipelines
vigil run --report html                  # Standalone HTML report

Parallel Execution

pip install "vigil-eval[parallel]"
vigil run --parallel 4

Configuration

Works with zero config. When you need it, create vigil.yaml:

defaults:
  cost_threshold: 0.05
  latency_threshold: 5.0
  semantic_threshold: 0.85

reporting:
  format: terminal
  verbose: true

Or add to your existing pyproject.toml:

[tool.vigil]
cost_threshold = 0.05
latency_threshold = 5.0

Plugins

Extend Vigil with custom assertions, agents, and reporters:

from vigil.plugins import register_assertion

@register_assertion("assert_polite")
def assert_polite(result, **kwargs):
    polite_words = ["please", "thank", "sorry", "appreciate"]
    if not any(word in result.output.lower() for word in polite_words):
        raise AssertionError("Output is not polite")

Plugins are auto-discovered via Python entry points.

How Vigil Compares

	Vigil	DeepEval	Promptfoo	RAGAS
Setup	pip install and go	Requires account signup	Node.js + YAML config	pip install + config
Write tests in	Python (pytest)	Python (pytest)	YAML	Python
Zero config	Yes	No	No	No
Agent testing	Functions, HTTP, CLI	Functions only	HTTP, CLI	RAG only
Async support	Built-in	Limited	N/A	No
Cost tracking	Auto (20+ models)	Manual	No	No
Snapshot testing	Built-in	No	No	No
LLM-as-judge	Yes	Yes	Yes	Yes
Plugin system	Yes	No	Yes	No
CI/GitHub Action	Included	Separate	Separate	No
Cloud required	No	Free tier limited	Optional	No
Lines to first test	5	15+	20+ (YAML)	10+

Vigil is built for developers who want pytest-like simplicity, not a platform.

Install

pip install vigil-eval                    # Core
pip install "vigil-eval[openai]"          # + OpenAI (LLM-as-judge, embeddings)
pip install "vigil-eval[anthropic]"       # + Anthropic
pip install "vigil-eval[all]"             # Everything

License

Apache 2.0