Salesforce CLI is a command-line interface that lets you run commands to create, test, and deploy Salesforce applications. You can easily integrate Salesforce CLI commands into various CI tools, such as CircleCI, Jenkins, or Travis CI, to automate testing and deployment of Salesforce applications against scratch orgs.
Salesforce CLI also supports the Salesforce DX development model, which enables source-driven development, team collaboration, and agile delivery. References:
* Continuous Integration | Salesforce DX Developer Guide
* Set Up Continuous Integration for Your Salesforce Projects | Salesforce Developers Blog
* Collaborate Using Continuous Integration Unit | Salesforce Trailhead