Docker, a leader in software container technologies, has acquired New York-based AtomicJar, a privately-held company behind the popular open source project Testcontainers, for an undisclosed sum. This acquisition, the seventh by Docker since 2019, continues the company’s focus on improving the end-to-end developer experience by acquiring startups to accelerate delivery of its vision.

The acquisition is a mix of equity and cash. Other terms of the deal were not disclosed.

“With its support for Java, .NET, Node.js, and other programming languages together with its container-based testing automation, Testcontainers has become the de facto standard test framework for the developer’s ‘inner loop’,” said Docker CEO Scott Johnston. “Why? The result speaks for itself – Testcontainers provides a step-function improvement in both the quality and speed of application delivery. We’re excited to add their strong, complementary offering to the Docker portfolio.”

Testcontainers is an open-source framework for provisioning throwaway, on-demand instances of containers for development and testing use cases. Testcontainers makes it easy to work with databases, message brokers, web browsers, or just about anything that can run in a Docker container. Testcontainers has transformed test-enabled development at leading engineering organizations like DoorDash, Spotify, Uber, and Netflix, becoming the de facto standard for dev-first testing. In 2022, Testcontainers saw an increase from 50 million to 100 million in Docker Hub pulls, making it one of the fastest-growing open-source projects in the testing category. It is currently being pulled more than 10 million times a month.

“Docker shares our goal of continuously improving the developer experience so that they can be more focused on innovating,” said Sergei Egorov, Testcontainers co-creator and CEO, AtomicJar. “We are excited to join Docker and are confident that our combination will vastly improve developer productivity while shipping software with confidence.”

AtomicJar is both the custodian of the Testcontainers OSS and has also delivered solutions for Testcontainers developers including Testcontainers Desktop – a companion application that enhances local development and testing; and Testcontainers Cloud – a cloud-based service that offloads the running of containers to the cloud, providing a consistent testing experience across different operating systems, enhancing developer productivity and team efficiency. With Testcontainers, Docker is now even easier to use in more ways meeting developers in IDE and the languages they already use: Java, .NET, Node, Go, or Haskells without YAML or other abstractions.