我有一堂課ResolverChainContext：public class ResolverChainContext {  private AWSCredentialsProvider assumeRoleCredentials;}在setup()單元測(cè)試（Groovy 和 Spock）中，我用 Mock 填充上面的字段：def setup() {  def ctx = ResolverChainContext.builder().build()  ctx.setAssumeRoleCredentials(Mock(AWSCredentialsProvider.class))}接下來在我的測(cè)試用例中，我調(diào)用了一個(gè)方法getDynamoDBCredentialsV2()，我想v1Credentials從中獲取getDynamoDBCredentials()來自 Mock 對(duì)象的setup()步驟：public interface AWSCredentialsProvider {    AWSCredentials getCredentials();    void refresh();}protected AWSCredentialsProvider getDynamoDBCredentials() {    final AWSCredentialsProvider fasCredentials = resolverChainContext.getFasCredentials();    final AWSCredentialsProvider roleCredentials = resolverChainContext.getAssumeRoleCredentials();    if (null == fasCredentials || !invokerConfig.isUseCallerCredentials()) {        return roleCredentials;    } else {        return fasCredentials;    }}protected AwsCredentialsProvider getDynamoDBCredentialsV2() {    AWSCredentials v1Credentials = getDynamoDBCredentials().getCredentials();    blahblahblah;}問題是我會(huì)得到null的v1Credentials。當(dāng)我調(diào)試它時(shí)，類型roleCredentials是“Mock for type AWSCredentialsProvider”。getCredentials()在調(diào)用它之后，它得到了null。這是因?yàn)槲义e(cuò)誤地使用了 Groovy 嗎？我怎樣才能使它v1Credentials成為應(yīng)該的對(duì)象？我應(yīng)該使用 Mock/Stub 嗎？