How to select custom theme in Magento integration tests?

I am writing an integration test for a Magento action. In the frontend I have selected a custom theme with custom layout files and I get the correct output.

But in the integration test the default theme Magento/luma is used, where the specific blocks, which should be shown in the frontend, are not available.

How can I select the correct theme in my integration tests? A solution that must not be repeated for each test is preferred.