Fixture.disableConcurrency Method
Disables concurrent test execution for a particular fixture.
Concurrent test execution is not suitable for tests that can only run in a certain order. To ignore the global concurrency setting for a particular fixture, use the disableConcurrency method.
Example
fixture`Fixture.disableConcurrency`
    .page`https://devexpress.github.io/testcafe/example/`
    .disableConcurrency;