Smart Assertions

The smart assertion is a simple way to assert both ordinary values and ZIO effects. It uses the assertTrue function, which uses macro under the hood.

Asserting Ordinary Values

In the following example, we assert simple ordinary values using the assertTrue method:

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

test("sum"){
  assertTrue(1 + 1 == 2)
}

Asserting ZIO effects

The assertTrue method can also be used to assert ZIO effects:

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

test("updating ref") {
  for {
    r <- Ref.make(0)
    _ <- r.update(_ + 1)
    v <- r.get
  } yield assertTrue(v == 1)
}

Using assertTrue with for-comprehension style, we can think of testing as these three steps:

1. Set up the test — In this section we should setup the system under test (e.g. Ref.make(0)).
2. Running the test — Then we run the test scenario according to the test specification. (e.g ref.update(_ + 1))
3. Making assertions about the test - Finally, we should assert the result with the right expectations (e.g. assertTrue(v == 1))