Test LLM Prompts At Scale

Create test cases, define assertions, and evaluate prompt performance across a wide range of inputs with Langtail's intuitive testing suite.

Comprehensive Testing Suite

Create and manage tests

Intuitive Test Creation Build tests using a user-friendly, Excel-like table interface.

Flexible Data Input Import test cases from CSV files or paste directly from Excel.

Efficient Test Management Organize tests into collections and run them against different prompt versions.

Test Run History Track and review past test runs to monitor performance over time.

Versatile Assertions

Evaluate prompt outputs with precision

String Manipulation Assertions Validate outputs using contains, exact, and other string-based assertions.

Custom JavaScript Assertions Write custom assertion functions in JavaScript for advanced evaluation.

External API Integration Verify outputs by calling external APIs within assertion functions.

LLM-powered Assertions Assess output quality, relevance, and truthfulness using LLM-based assertions.

Future-proof Testing

Upcoming features to enhance testing experience

Human-like Assertions Evaluate outputs using assertions that mimic human judgment.

API Data Retrieval Fetch data from APIs to use as inputs for tests, ideal for RAG apps.

Function Resolvers Call external APIs during function resolution for enhanced testing capabilities.

Assistant API Testing Expand testing capabilities to cover Langtail's Assistants API.

Engineering and AI teamsLangtail

"Langtail simplifies the development and testing of Deepnote AI, enabling our team to focus on further integrating AI features into our product"

Ondřej Romancov
@ondrejromancov

"This is already a killer tool for many use-cases we are already using it for. Super excited for the upcoming features and good luck with the launch and further development! 💜"

Jakub Žitný
@jakubzitny

"Been using LangTail for a few months now, highly recommend. It has kept me sane. If you want your LLM apps to behave uncontrollably all the time, don't use LangTail. On the other hand, if you are serious about the product you are building, you know what to do :P Love the product and the team's hard work. Keep up the great work!"

Sudhanshu Gautam
@sudhanshug16

"I have used Langtail for prompt refinement, and it was a real timesaver for me. Debugging and refining prompts is sometimes a tedious task, and Langtail makes it so much easier. Good work!"

Martin Staněk
@martin_stanek

"LLM products are creating a flurry of bad experiences in their rush to hit the market quickly. But Petr and his team have been demonstrating since day one just how serious they are about doing this job with outstanding designs. I've been following them for over a year now and I highly recommend them to everyone. I'm certain they're going to reach fantastic places."

Yiğit Konur
@yigitkonur

"Been using Langtail for a while, and it has made working with our clients a breeze"

Soham Adwani
@snazzyham

"Unpredictable behavior of LLMs, team collaboration on prompts and robust evaluation were the biggest pains for me when I was building my app. But now it's solved thanks to LangTail. It's a great product."

Michal Stoklasa
@michal_stoklasa

Frequently asked questions

1. What types of assertions are supported for evaluating prompt outputs?
2. Can I import test cases from external sources?
3. How can I track the performance of my prompts over time?
4. Can I compare the performance of different prompt versions?

Ready to test your prompts at scale?

Start testing and evaluating your prompts for free today.