How to skip Scala FunSuite tests under certain conditions?

Suppose I have some tests that I want to only run if some environment variable is set and the value is valid. How do I do this with Scala FunSuite?

For instance:

class Tests extends FunSuite {
  before {
    // Test if the environment variable is set and value is valid
  }

  test("foo") {
    ...
  }
}

Test foo should only run when the check in the before call succeeded. I tried to use assume but it failed with TestCanceledException.