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How does the Agent configure tests to run on Testcontainers Cloud?

This article explains how the Testcontainers Cloud Agent relies on the ~/.testcontainers.properties file to inform the Testcontainers libraries that they should prefer Testcontainers Cloud.

Sometimes a system has access to both a Docker daemon and Testcontainers Cloud. To resolve which Docker environment to use Testcontainers libraries do the following in order:

  • Obtain Docker location from the environment variable DOCKER_HOST
  • Read the ~/.testcontainers.properties file (if it exists):
    • Find the Docker location is from its docker.host property
  • Fall back to trying the default Docker locations for the current operating system 

Testcontainers Cloud Agent, both Desktop and CI, configures its own location in the ~/.testcontainers.properties file, which makes the tests automatically prefer it, unless the user explicitly defined a DOCKER_HOST environment variable. 

You can also configure individual projects not to consider the configuration in the ~/.testcontainers.properties file.