Agile development requires agile testing practices and one of the key elements of this is automation. Test automation involves performing software testing activities with little or no human interaction, in order to achieve greater speed and efficiency. This is especially useful if you need to frequently run regression tests.
Regarding the test pyramid, teams must sooner or later start writing API and/or UI automation tests. The typical technology stack is .NET or Java with Selenium WebDriver; however, we can align the test stack with the technologies used in the development stack. Thus, we can use RobotFramework for Python projects, Cypress.io for Javascript or Behat/Behave for Drupal or PHP frameworks. The crucial aspect is to have an interface to the continuous integration/deployment framework - we can integrate, for example, with MS Team Foundation Server, Atlassian Jira or Gitlab. Where desired, mobile support using Appium can be in place.