Why we have to specify useTestNG() for tests with Gradle?

Question

If we want to use for our test TestNG we have to write something like:

dependencies {
   compile project(':model')
   testCompile 'org.testng:testng:6.8'
}

test.useTestNG()

But when using Spock we specify just the dependency

dependencies {
   compile project(':model')
   testCompile 'org.spockframework:spock-core:0.7-groovy-2.0'
}

Why we have to specify test.useTestNG()?

Answer 1

Spock tests get run via JUnit, which is the Gradle default. Alternatively, tests can be run via TestNG.