Callee.java

public class Callee {

	public void execute(int i) {
		System.out.println(i);
	}
}

TestTarget.java

public class TestTarget {

	Callee callee;

	public TestTarget(Callee callee) {
		this.callee = callee;
	}

	public void invoke(int i) {
		callee.execute(i * 100);
	}
}

TestVoid.java

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class TestVoid {

	@Test
	public void testInvoke() throws Exception {
		TestTarget target = new TestTarget(new Callee() {
			@Override
			public void execute(int i) {
				assertEquals(100, i);
			}
		});

		target.invoke(1);
	}

}