I created simple test cases.

import org.junit.Assert;
import org.junit.Test;

public class TestCaffeineBuzz {
@Test
public void testOutputJava() {
Assert.assertEquals("Java", CaffeineBuzz.caffeineBuzz(3));
}

@Test
public void testOutputJavaScript() {
	Assert.assertEquals("JavaScript", CaffeineBuzz.caffeineBuzz(6));
}

@Test
public void testOutputCoffeeScript() {
	Assert.assertEquals("CoffeeScript", CaffeineBuzz.caffeineBuzz(12));
}

@Test
public void testOutputMochaMissing() {
	Assert.assertEquals("mocha_missing!", CaffeineBuzz.caffeineBuzz(1));
}

}