scala-example.md

gwt-test example - Scala

There are several significant differences in the use of gwt-test in Scala compared to Java and Groovy:

1. The context class is declared inside of an object at the top of the test class, and the test implementation is contained in the companion class.
2. Fields in the context class must be vars and must be explicitly initialized. You can use the default value constant _ for this purpose, as in var field = _.
3. In Scala, given and then are reserved words and cannot be used as method names. To call those methods in a Scala test, enclose the method names in backquotes: `given` and `then`. You can also enclose the method names when and and in backquotes for the sake of consistency.
4. When instantiating the test object, the type argument is specified as classOf[class-name] so that the Java framework can instantiate it.
5. Test methods return Unit, which is the Scala equivalent of the Java void type.

Here's an example of a gwt-test written in Scala:

package gwttest.example

import gwttest.example.DivisionTest.TestContext
import io.github.mmbishop.gwttest.core.GwtTest
import io.github.mmbishop.gwttest.functions.GwtFunction
import io.github.mmbishop.gwttest.functions.GwtFunctionWithArgument
import io.github.mmbishop.gwttest.model.Context
import org.junit.jupiter.api.Test
import org.hamcrest.CoreMatchers.is
import org.hamcrest.MatcherAssert.assertThat
import org.junit.jupiter.api.Assertions.assertTrue

object DivisionTest {
  class TestContext extends Context {
    var dividend: Double = _
    var divisor: Double = _
    var quotient: Double = _
  }
}

class DivisionTest {

  @Test
  def quotient_of_two_numbers_is_calculated(): Unit = {
    gwt.test()
      .`given`(a_dividend, 12.0)
      .and(a_divisor, 4.0)
      .when(dividing_the_dividend_by_the_divisor)
      .`then`(the_quotient_is, 3.0)
  }

  @Test
  def dividing_a_number_by_zero_results_in_infinity(): Unit = {
    gwt.test()
      .`given`(a_dividend, 6.0)
      .when(dividing_the_dividend_by_zero)
      .`then`(the_quotient_is_infinity)
  }

  private val gwt: GwtTest[TestContext] = new GwtTest[TestContext](classOf[TestContext])

  private val a_dividend: GwtFunctionWithArgument[TestContext, Double]
      = (context, dividend) => context.dividend = dividend

  private val a_divisor: GwtFunctionWithArgument[TestContext, Double]
      = (context, divisor) => context.divisor = divisor

  private val dividing_the_dividend_by_the_divisor: GwtFunction[TestContext]
      = context => context.quotient = context.dividend / context.divisor

  private val dividing_the_dividend_by_zero: GwtFunction[TestContext]
      = context => context.quotient = context.dividend / 0.0

  private val the_quotient_is: GwtFunctionWithArgument[TestContext, Double]
      = (context, expectedQuotient) => assertThat(context.quotient, is(expectedQuotient))

  private val the_quotient_is_infinity: GwtFunction[TestContext]
      = context => assertTrue(context.quotient.isPosInfinity)

}