How to unit test a gradle plugin using the gradle build itself - gradle

Question

I have a simple gradle plugin that I'd like to test drive but I'm unsure how to "ask" gradle to run my tests
Here is the block I'd like to modify (at the top of my gradle build file)
buildscript {
dependencies {
classpath('org.testng.testng:6.8.8')
}
}
when I run "gradle" from the command line I do get the following in my output
:buildSrc:compileJava UP-TO-DATE :buildSrc:compileGroovy UP-TO-DATE
:buildSrc:processResources UP-TO-DATE :buildSrc:classes UP-TO-DATE
:buildSrc:jar UP-TO-DATE :buildSrc:assemble UP-TO-DATE
:buildSrc:compileTestJava UP-TO-DATE :buildSrc:compileTestGroovy
UP-TO-DATE :buildSrc:processTestResources UP-TO-DATE
:buildSrc:testClasses UP-TO-DATE :buildSrc:test UP-TO-DATE
:buildSrc:check UP-TO-DATE :buildSrc:build UP-TO-DATE :help
This makes me think I am running the "tests" in my directory (structured like the below).
.
├── main
│   └── groovy
│   └── foobar
│   └── gradle
│   ├── cat
│   │   ├── CatFile.groovy
│   └── TaskHelper.groovy
└── test
└── groovy
└── foobar
└── gradle
└── cat
└── CatFileTest.groovy
Yet nothing is run (I'd expect to see my CatFileTest fail) -here is my test file
package foobar.gradle.cat
import org.testng.annotations.Test
class CatFileTest {
#Test
void shouldBlowUp() {
assert 1 == 2
}
}

Answer 1

Sounds like the classes of your plugin sit under buildSrc. If that's the case you'll have to declare the dependency on TestNG in a build.gradle file under buildSrc. The contents would look as such:
repositories {
mavenCentral()
}
dependencies {
testCompile 'org.testng.testng:6.8.8'
}
To use TestNG as test framework, you'll have to reconfigure the default test task provided by the Java plugin as described in Mark's answer.

Answer 2

Default testing framework is JUnit. You'll have to explicitly enable TestNG support.
test {
useTestNG()
}