As developers work with an increasing number of third-party APIs, they need a tool that mocks those APIs for testing purposes without actually firing the API gateway. Mock APIs mirror the behavior of APIs, letting developers test them in a sandbox environment.

WireMock has emerged in recent years as a popular open source tool for API mocking, and last year the project founder Tom Akehurst teamed up with Uri Maoz to launch a company with the same name, based on the open source project. They created a managed cloud service called WireMock Cloud, and today announced a $6.5 million seed investment.

Maoz, who serves as the startup’s CEO, says that by creating a mock, you can safely work out different scenarios without actually using the API. “Now you have an environment where you can actually access all of the APIs that you depend on, but with no dependency on the actual third-party API, because everything is working against mock,” he told TechCrunch.

What’s more, the mocks are dynamic, so you can test against different use cases, all without actually activating the API until you are ready to launch to users.

There are several ways to create API mocks in WireMock, including creating it manually, importing the API specification or using the tool’s SDK to automate the process. Finally, it can record API traffic to see how it works.

With this final method, WireMock Cloud watches how an app interacts with a live API by recording the traffic between them to figure out what the API is doing. The platform then automatically creates a mock API based on what it learned from the live traffic.

Akehurst, who is CTO, created the first version of the open source WireMock project back in 2011 as a side project. The open source version has grown extremely popular over the year, and today it has 4 million downloads a month, according to Maoz . Last year the two men decided to launch a company and build a managed cloud version of WireMock.

In addition to the open source version, which anyone can download, there is a free tier of the managed cloud, which Maoz says will be free forever. The reason for this dual strategy is because the founders recognized that not everyone would be comfortable working with open source, and they still wanted to provide a way for developers to try the product without paying.

“We have a ‘free forever’ edition because we truly believe that customers should be able to try the product, and some customers aren’t even familiar with the open source version and they want to try the product,” he said.

The company already has around 100 customers using the paid version, including IBM, NIH and Intuit, along with 10 employees. Maoz says they plan to double in size in the next year, and as they do, he says diversity has always been a priority for him, and will continue to be as he hires the next wave of employees.

“We are a small company right now, but this is an important topic that I was also paying attention to at my previous companies, where I managed large teams. So it’s definitely something that is important for us and we are paying attention to that as we grow,” he said.

Today’s seed investment was led by Ridge Ventures, with participation from First Rays Venture Partners, Scribble Ventures and several unnamed angel investors.