Scala Testing with ScalaCheck
Examples
Scalacheck with scalatest and error messages
Example of usage scalacheck with scalatest. Below we have four tests:
• "show pass example" - it passes
•"show simple example without custom error message " - just failed message without details, && boolean operator is used
•"show example with error messages on argument" - error message on argument ("argument" |:) Props.all method is used instead of &&
•"show example with error messages on command" - error message on command ("command" |:) Props.all method is used instead of &&
import org.scalatest.prop.Checkers
import org.scalatest.{Matchers, WordSpecLike}
import org.scalacheck.Gen._
import org.scalacheck.Prop._
import org.scalacheck.Prop
object Splitter {
def splitLineByColon(message: String): (String, String) = {
val (command, argument) = message.indexOf(":") match {
case -1 =>
(message, "")
case x: Int =>
(message.substring(0, x), message.substring(x + 1))
}
(command.trim, argument.trim)
}
def splitLineByColonWithBugOnCommand(message: String): (String, String) = {
val (command, argument) = splitLineByColon(message)
(command.trim + 2, argument.trim)
}
def splitLineByColonWithBugOnArgument(message: String): (String, String) = {
val (command, argument) = splitLineByColon(message)
(command.trim, argument.trim + 2)
}
}
class ScalaCheckSpec extends WordSpecLike with Matchers with Checkers {
private val COMMAND_LENGTH = 4
"ScalaCheckSpec " should {"show pass example" in {
check {
Prop.forAll(listOfN(COMMAND_LENGTH, alphaChar), alphaStr) {
(chars, expArgument) =>
val expCommand = new String(chars.toArray)
val line = s"$expCommand:$expArgument"
val (c, p) = Splitter.splitLineByColon(line)
Prop.all("command" |: c =? expCommand, "argument" |: expArgument =? p)
}
}
}"show simple example without custom error message " in {
check {
Prop.forAll(listOfN(COMMAND_LENGTH, alphaChar), alphaStr) {
(chars, expArgument) =>
val expCommand = new String(chars.toArray)
val line = s"$expCommand:$expArgument"
val (c, p) = Splitter.splitLineByColonWithBugOnArgument(line)
c === expCommand && expArgument === p
}
}
}
"show example with error messages on argument" in {
check {
Prop.forAll(listOfN(COMMAND_LENGTH, alphaChar), alphaStr) {
(chars, expArgument) =>
val expCommand = new String(chars.toArray)
val line = s"$expCommand:$expArgument"
val (c, p) = Splitter.splitLineByColonWithBugOnArgument(line)
Prop.all("command" |: c =? expCommand, "argument" |: expArgument =? p)
}
}
}"show example with error messages on command" in {
check {
Prop.forAll(listOfN(COMMAND_LENGTH, alphaChar), alphaStr) {
(chars, expArgument) =>
val expCommand = new String(chars.toArray)
val line = s"$expCommand:$expArgument"
val (c, p) = Splitter.splitLineByColonWithBugOnCommand(line)
Prop.all("command" |: c =? expCommand, "argument" |: expArgument =? p)
} }
}
The output (fragments):
[info] - should show example // passed
[info] - should show simple example without custom error message *** FAILED ***
[info] (ScalaCheckSpec.scala:73)
[info] Falsified after 0 successful property evaluations.
[info] Location: (ScalaCheckSpec.scala:73)
[info] Occurred when passed generated values (
[info] arg0 = List(), // 3 shrinks
[info] arg1 = ""
[info] )
[info] - should show example with error messages on argument *** FAILED ***
[info] (ScalaCheckSpec.scala:86)
[info] Falsified after 0 successful property evaluations.
[info] Location: (ScalaCheckSpec.scala:86)
[info] Occurred when passed generated values (
[info] arg0 = List(), // 3 shrinks
[info] arg1 = ""
[info] )
[info] Labels of failing property:
[info] Expected "" but got "2"
[info] argument
[info] - should show example with error messages on command *** FAILED ***
[info] (ScalaCheckSpec.scala:99)
[info] Falsified after 0 successful property evaluations.
[info] Location: (ScalaCheckSpec.scala:99)
[info] Occurred when passed generated values (
[info] arg0 = List(), // 3 shrinks
[info] arg1 = ""
[info] )
[info] Labels of failing property:
[info] Expected "2" but got ""
[info] command