如何为此测试生成异常？

Question

我正在尝试在我的应用程序中测试异常处理程序。但是，我无法为构造函数生成异常。

通常，我会创建一个对象的最小起订量，然后进行设置，其中对Object.method的调用将引发异常。然后只需在测试中检测异常即可。

但是，在此构造方法中，唯一的调用是：

CredentialProfileStoreChain.TryGetAWSCredentials

CredentialProfileStoreChain.TryGetAWSCredentials无法被覆盖，因此我无法使用moq安装程序来生成异常。

代码：

public class AWSDynamoDbManager : IAWSDynamoDbManager
{
    private readonly ILogger _logger;
    private readonly AmazonDynamoDBClient _dynamoDbClient;
    //NOTE:  This setting is in the app.config of the calling application so that different uses can use different profiles
    private readonly string _awsProfileName = ConfigurationManager.AppSettings["AWSProfileName"];

    public AWSDynamoDbManager(CredentialProfileStoreChain chain, ILogger logger)
    {
       this._logger = logger;

       try
       {
           AWSCredentials awsCredentials;
           chain.TryGetAWSCredentials(_awsProfileName, out awsCredentials);
           _dynamoDbClient = new AmazonDynamoDBClient(awsCredentials, RegionEndpoint.EUWest2);
       }
       catch (Exception e)
       {
           logger.Error("Could Not Open DynamoDB");
           logger.Error("Error: " + e.Message);
           throw;
       }
   }
}

测试：

public void TestToSeeIfWeCatchTheExceptionIfWeCannotConnectToTheDatabase()
    {
        // arrange
        var mockLogger = new Mock<ILogger>();
        var mockChain = new Mock<CredentialProfileStoreChain>();

        // act / assert
        Assert.Catch<ArgumentException>(() => new AWSDynamoDbManager(mockChain.Object, mockLogger.Object));
    }

我可以使用什么来强制构造函数引发异常？

Answer 1

当我的手由于外部依赖性或静态类型而被束缚时，我使用包装器，因此这就是我在这里使用的。由于我们无法模拟CredentialProfileStoreChain，因此将其放入包装器中并使用该包装器。

public interface ICredentialProfileStoreChainWrapper
{
    void TryGetAWSCredentials(/*TODO*/);
}
public class CredentialProfileStoreChainWrapper
{
    readonly CredentialProfileStoreChain _Chain;
    public CredentialProfileStoreChainWrapper(CredentialProfileStoreChain chain)
    {
        _Chain = chain;
    }
    public void TryGetAWSCredentials(/*TODO*/)
    {
        _Chain.TryGetAWSCredentials(/*TODO*/);
    }
}
public class AWSDynamoDbManager : IAWSDynamoDbManager
{
    public AWSDynamoDbManager(ICredentialProfileStoreChainWrapper chainWrapper, ILogger logger)
    {
        //TODO
        chainWrapper.TryGetAWSCredentials(/*TODO*/);
    }
}
public class Tests
{
    [Test]
    public void TestToSeeIfWeCatchTheExceptionIfWeCannotConnectToTheDatabase()
    {
        var wrapper = new Mock<ICredentialProfileStoreChainWrapper>();
        var logger = new Mock<ILogger>();
        var manager = new AWSDynamoDbManager(wrapper.Object, logger.Object);
        wrapper.Setup(s => s.TryGetAWSCredentials(/*TODO*/)).Throws(new Exception());
        //TODO
    }
}