@Test
public void testToString() {

    TestDefaultHeaders headers = newInstance();
    headers.add(of("name1"), of("value1"));
    headers.add(of("name1"), of("value2"));
    headers.add(of("name2"), of("value3"));
    assertEquals("TestDefaultHeaders[name1: value1, name1: value2, name2: value3]", headers.toString());
    headers = newInstance();
    headers.add(of("name1"), of("value1"));
    headers.add(of("name2"), of("value2"));
    headers.add(of("name3"), of("value3"));
    assertEquals("TestDefaultHeaders[name1: value1, name2: value2, name3: value3]", headers.toString());
    headers = newInstance();
    headers.add(of("name1"), of("value1"));
    assertEquals("TestDefaultHeaders[name1: value1]", headers.toString());
    headers = newInstance();
    assertEquals("TestDefaultHeaders[]", headers.toString());
}