To run unit test cases using rest assured framework in adobe cq6 insatance

@Test
public void testExecute() throws Exception {
        Response res = get("http://localhost:4502/payback/cr.json/getPersonPath");
        assertEquals(200, res.getStatusCode());
}

I have added dependencies to classpath, but still while running test cases i am getting the following exception, why?

java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
    at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:156)