@Override
    public String toString() {
        return "MergePolicyConfig{"
                + "policy='" + policy + '\''
                + ", batchSize=" + batchSize
                + '}';
    }
@Test
    public void testToString() {
        config.setPolicy(HigherHitsMergePolicy.class.getName());
        config.setBatchSize(2342);

        String configString = config.toString();
        assertThat(configString).contains("MergePolicyConfig");
        assertThat(configString).contains("policy='" + HigherHitsMergePolicy.class.getName() + "'");
        assertThat(configString).contains("batchSize=2342");
    }