amazon-web-services - 你如何模拟 *ec2.DescribeVolumes 输出的值

Question

我目前正在努力适应 TDD，在我正在进行的当前项目中，我正在尝试利用 AWS 的 Go SDK。这一切都很好，花花公子，我以前用过它，但我目前正在尝试模拟 *ec2.DescribeVolumesOutput 发送的值。

深入研究代码，我将其视为 *ec2.DescribeVolumesOutput 的返回值:

type DescribeVolumesOutput struct {
    _ struct{} `type:"structure"`

    // The NextToken value to include in a future DescribeVolumes request. When
    // the results of a DescribeVolumes request exceed MaxResults, this value can
    // be used to retrieve the next page of results. This value is null when there
    // are no more results to return.
    NextToken *string `locationName:"nextToken" type:"string"`

    // Information about the volumes.
    Volumes []*Volume `locationName:"volumeSet" locationNameList:"item" type:"list"`
}

好吧.. 这很酷，但我想模拟的输出必须位于 Volumes []*VolumelocationName:"volumeSet"locationNameList:"item"type:"list"`所以让我们更深入一点，看看那是什么......

type Volume struct {
    _ struct{} `type:"structure"`

    // Information about the volume attachments.
    Attachments []*VolumeAttachment `locationName:"attachmentSet" locationNameList:"item" type:"list"`

    // The Availability Zone for the volume.
    AvailabilityZone *string `locationName:"availabilityZone" type:"string"`

    // The time stamp when volume creation was initiated.
    CreateTime *time.Time `locationName:"createTime" type:"timestamp"`

    // Indicates whether the volume will be encrypted.
    Encrypted *bool `locationName:"encrypted" type:"boolean"`

    // The number of I/O operations per second (IOPS) that the volume supports.
    // For Provisioned IOPS SSD volumes, this represents the number of IOPS that
    // are provisioned for the volume. For General Purpose SSD volumes, this represents
    // the baseline performance of the volume and the rate at which the volume accumulates
    // I/O credits for bursting. For more information, see Amazon EBS Volume Types
    // (https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSVolumeTypes.html)
    // in the Amazon Elastic Compute Cloud User Guide.
    //
    // Constraints: Range is 100-16,000 IOPS for gp2 volumes and 100 to 64,000IOPS
    // for io1 volumes, in most Regions. The maximum IOPS for io1 of 64,000 is guaranteed
    // only on Nitro-based instances (https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-types.html#ec2-nitro-instances).
    // Other instance families guarantee performance up to 32,000 IOPS.
    //
    // Condition: This parameter is required for requests to create io1 volumes;
    // it is not used in requests to create gp2, st1, sc1, or standard volumes.
    Iops *int64 `locationName:"iops" type:"integer"`

    // The full ARN of the AWS Key Management Service (AWS KMS) customer master
    // key (CMK) that was used to protect the volume encryption key for the volume.
    KmsKeyId *string `locationName:"kmsKeyId" type:"string"`

    // The size of the volume, in GiBs.
    Size *int64 `locationName:"size" type:"integer"`

    // The snapshot from which the volume was created, if applicable.
    SnapshotId *string `locationName:"snapshotId" type:"string"`

    // The volume state.
    State *string `locationName:"status" type:"string" enum:"VolumeState"`

    // Any tags assigned to the volume.
    Tags []*Tag `locationName:"tagSet" locationNameList:"item" type:"list"`

    // The ID of the volume.
    VolumeId *string `locationName:"volumeId" type:"string"`

    // The volume type. This can be gp2 for General Purpose SSD, io1 for Provisioned
    // IOPS SSD, st1 for Throughput Optimized HDD, sc1 for Cold HDD, or standard
    // for Magnetic volumes.
    VolumeType *string `locationName:"volumeType" type:"string" enum:"VolumeType"`
}

不错!这看起来像是我想模拟其值的一些数据!

但在过去的几天里，我并没有真正 mock 这些值(value)观。它们是否如此嵌套以至于这种类型的 mock 不值得付出努力？即使尝试使用 github.com/aws/aws-sdk-go/service/ec2/ec2iface 似乎也无法帮助我解决如何正确打包一些模拟值返回以进行测试的问题。我来参加 TDD 是不是全错了？我错过了一些非常明显的东西吗？我真的没有示例代码可以展示，因为我现在不再理解我想要做什么。

有没有人可以举例说明他们是如何 mock 这个的？

Answer 1

没有办法模拟类型，你只能模拟接口(interface)的实现。在你的情况下，我假设你正在尝试调用 DescribeVolumes并在响应中获取由您构造的值。
为此，您需要创建一个像

这样的模拟

type MockEC2API struct {
    ec2iface.EC2API // embedding of the interface is needed to skip implementation of all methods
    DescribeVolumesMethod func(*ec2.DescribeVolumesInput) (*ec2.DescribeVolumesOutput, error)
}

func (m *MockEC2API) DescribeVolumes(in *ec2.DescribeVolumesInput) (*ec2.DescribeVolumesOutput, error) {
    if m.DescribeVolumesMethod != nil {
        return m.DescribeVolumesMethod(in)
    }
    return nil, nil // return any value you think is good for you
}

在测试中创建 MockEC2API 实例而不是真正的 ec2.EC2 并为其提供将被调用的函数并返回您准备好的 ec2.DescribeVolumesOutput 结果

...
ec2 := &MockEC2API{
    DescribeVolumesMethod: func(*ec2.DescribeVolumesInput) (*ec2.DescribeVolumesOutput, error) {
        return &ec2.DescribeVolumesOutput{...your initialization...}, nil
    }
}
...
output, err := ec2.DescribeVolumes(in) // this output will be your prepared initialization