Kobalt automatically detects how to run your tests based on the test dependencies that you declared:

dependenciesTest {
    compile("org.testng:testng:6.9.9")
}

By default, Kobalt supports TestNG, JUnit and Spek. You can also configure how your tests run
with the test{} directive:

test {
    args("-excludegroups", "broken", "src/test/resources/testng.xml")
}

The full list of configuration parameters can be found in the TestConfig class.

Additionally, you can define multiple test configurations, each with a different name. Each
configuration will create an additional task named "test" followed by the name of
that configuration. For example:

test {
    args("-excludegroups", "broken", "src/test/resources/testng.xml")
}

test {
    name = "All"
    args("src/test/resources/testng.xml")
}

The first configuration has no name, so it will be launched with the task "test",
while the second one can be run with the task "testAll".

The full series of articles on Kobalt can be found here.