Configuring Tests

To run cases, there are some default configuration settings which are used by test runner, such as repeats, retries, samples and shrinks. We can change these settings using test aspects:

Number of Repeats

The repeats(n: Int) test aspect runs each test with the number of times to repeat tests to ensure they are stable set to the specified value:

import zio._
import zio.test.{ test, _ }

test("repeating a test") {
  ZIO.attempt("Repeating a test to ensure its stability")
    .debug
    .map(_ => assertTrue(true))
} @@ TestAspect.nonFlaky @@ TestAspect.repeats(5)

Number of Retries

The retries(n: Int) test aspect runs each test with the number of times to retry flaky tests set to the specified value.

Number of Samples

The samples(n: Int) test aspect runs each test with the number of sufficient samples to check for a random variable set to the specified value.

Let's change the number of default samples in the following example:

import zio._
import zio.test.{ test, _ }

test("customized number of samples") {
  for {
    ref <- Ref.make(0)
    _ <- check(Gen.int)(_ => assertZIO(ref.update(_ + 1))(Assertion.anything))
    value <- ref.get
  } yield assertTrue(value == 50)
} @@ TestAspect.samples(50)

Maximum Number of Shrinks

The shrinks(n: Int) test aspect runs each test with the maximum number of shrinkings to minimize large failures set to the specified value.