模拟 Javascript AWS.RDS.Signer

Question

我有用于通过 IAM 身份验证连接到 AWS Rds 代理的 Connection 类。该过程的一部分是创建令牌。我有一个创建令牌的函数，但现在我很难模拟和测试它。

这是带有setToken 方法的Connection 类：

class Connection {
    constructor(username, endpoint, database) {
        this.username = username;
        this.endpoint = endpoint;
        this.database = database;
    }

    setToken () {
        let signer = new AWS.RDS.Signer({
            region: 'us-east-1', // example: us-east-2
            hostname: this.endpoint,
            port: 3306,
            username: this.username
        });

        this.token = signer.getAuthToken({
            username: this.username
        });
    }
}

在这里我试图模拟AWS.RDS.Signer.getAuthToken()的返回值

test('Test Connection setToken', async () => {
    AWSMock.setSDKInstance(AWS);
    AWSMock.mock('RDS.Signer', 'getAuthToken', 'mock-token');


    let conn = new connections.Connection(
        'testUser',
        'testEndpoint',
        'testDb');

    conn.setToken();

    console.log(conn.token);
});

我希望看到“mock-token”作为conn.token 的值，但我得到的是：

{
  promise: [Function],
  createReadStream: [Function: createReadStream],
  on: [Function: on],
  send: [Function: send]
}

如何让AWS.RDS.Signer.getAuthToken() 返回一个模拟令牌？

---

尝试@ggordon 的解决方案后进行编辑

我试图通过将AWS 注入构造函数来使其工作，但似乎仍然遇到同样的问题。我认为我的部分问题是 AWS.RDS.Signer 不支持承诺，但我不完全确定。

这是我的新代码：

生成令牌的Token 类。 从“aws-sdk”导入 AWS；

class Token {
    constructor(awsInstance) {
        this.awsInstance = awsInstance || AWS;
    }

    getToken () {
        const endpoint = 'aurora-proxy.proxy.rds.amazonaws.com';

        const signer = new this.awsInstance.RDS.Signer({
            region: 'my-region',
            hostname: endpoint,
            port: 3306,
            username: 'myUser'
        });

        const token = signer.getAuthToken({
                username: 'svcLambda'
            });

        console.log ("IAM Token obtained\n");
        return token
    }
}

module.exports = { Token };

还有测试：

test('Should test getToken from Token', async () => {
    AWSMock.setSDKInstance(AWS);
    AWSMock.mock('RDS.Signer', 'getAuthToken', 'mock-token');

    let tokenObject = new tokens.Token(AWS);
    const token = tokenObject.getToken();

    console.log(token);
    expect(token).toStrictEqual('mock-token');
});

Token 类本身可以工作——它创建令牌，并且令牌可用于成功连接到 RDS。但是，单元测试失败，返回的实际令牌（来自 console.log）是这样的：

{
  promise: [Function],
  createReadStream: [Function: createReadStream],
  on: [Function: on],
  send: [Function: send]
}

这里也是@GSSWain 要求的package.json

{
  "name": "mylambda",
  "version": "0.0.1",
  "description": "My description.",
  "repository": {
    "type": "git",
    "url": ""
  },
  "scripts": {
    "lint": "eslint src/**/*.js __tests__/**/*.js",
    "prettier": "prettier --write src/**/*.js __tests__/**/*.js",
    "prettier:ci": "prettier --list-different src/**/*.js  __tests__/**/*.js",
    "test": "cross-env NODE_ENV=test jest",
    "test:coverage": "cross-env CI=true jest --coverage --watchAll=false -u --reporter=default --reporters=jest-junit",
    "build": "npm run build:dev",
    "build:dev": "cross-env NODE_ENV=development webpack --config webpack.config.js"
  },
  "dependencies": {
    "mysql2": "^2.2.5"
  },
  "devDependencies": {
    "@babel/core": "^7.6.4",
    "@babel/preset-env": "^7.6.3",
    "aws-sdk": "^2.552.0",
    "aws-sdk-mock": "^5.1.0",
    "babel-jest": "^24.9.0",
    "babel-loader": "^8.0.6",
    "babel-plugin-transform-es2015-modules-commonjs": "^6.26.2",
    "cross-env": "^6.0.3",
    "eslint": "^6.5.1",
    "eslint-config-prettier": "^6.4.0",
    "eslint-plugin-jest": "^22.19.0",
    "jest": "^24.9.0",
    "jest-junit": "^10.0.0",
    "prettier": "^1.18.2",
    "sinon": "^9.0.3"
  },
  "jest": {
    "verbose": true,
    "transform": {
      "^.+\\.js$": "babel-jest"
    },
    "globals": {
      "NODE_ENV": "test"
    },
    "moduleFileExtensions": [
      "js"
    ],
    "moduleDirectories": [
      "node_modules",
      "src"
    ],
    "coverageThreshold": {
      "global": {
        "statements": 100,
        "branches": 100,
        "functions": 100,
        "lines": 100
      }
    }
  },
  "jest-junit": {
    "outputName": "junit_jest.xml"
  }
}

Answer 1

问题

您的测试范围内的AWS 实例/对象与您的setToken 方法中使用的AWS 实例/对象不同。

aws-sdk-mock 模拟这个实例

由于转译，使用 TypeScript 或 ES6 编写的代码可能无法正确模拟，因为在 aws-sdk-mock 中创建的 aws-sdk 对象将不等于在要测试的代码中创建的对象。

require 也将返回一个新实例。

本质上，您是在模拟测试中的一个实例，而您的实际代码正在使用另一个未被模拟的实例。

可能的解决方案

解决方案 1

您可以修改您的代码以允许您有选择地注入所需的AWS 实例以使用例如

import AWS from 'aws-sdk';
class Connection {
    constructor(username, endpoint, database,awsInstance) {
        this.username = username;
        this.endpoint = endpoint;
        this.database = database;
        //if the awsInstance is null  or not provided use the default
        this.awsInstance = awsInstance || AWS;
    }

    setToken () {
        let signer = new this.awsInstance.RDS.Signer({
            region: 'us-east-1', // example: us-east-2
            hostname: this.endpoint,
            port: 3306,
            username: this.username
        });

        this.token = signer.getAuthToken({
            username: this.username
        });
    }
}

您的代码不需要任何修改，但是现在您可以选择在测试中进行

test('Test Connection setToken', async () => {
    AWSMock.setSDKInstance(AWS);
    AWSMock.mock('RDS.Signer', 'getAuthToken', 'mock-token');


    let conn = new connections.Connection(
        'testUser',
        'testEndpoint',
        'testDb',
        AWS //pass mock instance
        );

    conn.setToken();
    let actualToken = (await conn.token.promise());

    console.log(conn.token);
    console.log(actualToken);
});

这只是基于构造函数的注入，您可以在setToken 方法中进行类似的注入。

您还会注意到，在aws-sdk-mock 提供的示例和上面的示例中，我们从返回的promise 对象中提取了结果。这是因为mock implementation 返回一个承诺对象，尽管aws-sdk 尤其是AWS.RDS.Signer.getAuthToken 支持同步操作。 这是基于您正在使用的库的约束。

解决方案 2

如果您对基于此处共享的示例的同步调用感兴趣，您可能需要考虑另一个模拟库，这样可以更好地模拟您的代码/流程。另一种选择是考虑对您的实现进行异步/承诺重写。我把这个决定留给你。

一个简单的替代方案可能是：

test('Test Connection setToken', async () => {
    AWS.RDS.Signer = function MockSigner() {
        return {
            getAuthToken: function MockGetAuthToken(){ return 'mock-token'; }
        };
    };


    let conn = new connections.Connection(
        'testUser',
        'testEndpoint',
        'testDb',
        AWS //pass mock instance
        );

    conn.setToken();

    console.log(conn.token);
});

其他参考资料

我已经包含了用于模拟从 https://github.com/dwyl/aws-sdk-mock/blob/master/index.js#L118 检索到的 aws-sdk-mock 函数的方法的 sn-p。你会看到它创建并返回一个request

function mockServiceMethod(service, client, method, replace) {
  services[service].methodMocks[method].stub = sinon.stub(client, method).callsFake(function() {
    const args = Array.prototype.slice.call(arguments);

    let userArgs, userCallback;
    if (typeof args[(args.length || 1) - 1] === 'function') {
      userArgs = args.slice(0, -1);
      userCallback = args[(args.length || 1) - 1];
    } else {
      userArgs = args;
    }
    const havePromises = typeof AWS.Promise === 'function';
    let promise, resolve, reject, storedResult;
    const tryResolveFromStored = function() {
      if (storedResult && promise) {
        if (typeof storedResult.then === 'function') {
          storedResult.then(resolve, reject)
        } else if (storedResult.reject) {
          reject(storedResult.reject);
        } else {
          resolve(storedResult.resolve);
        }
      }
    };
    const callback = function(err, data) {
      if (!storedResult) {
        if (err) {
          storedResult = {reject: err};
        } else {
          storedResult = {resolve: data};
        }
      }
      if (userCallback) {
        userCallback(err, data);
      }
      tryResolveFromStored();
    };
    const request = {
      promise: havePromises ? function() {
        if (!promise) {
          promise = new AWS.Promise(function (resolve_, reject_) {
            resolve = resolve_;
            reject = reject_;
          });
        }
        tryResolveFromStored();
        return promise;
      } : undefined,
      createReadStream: function() {
        if (replace instanceof Readable) {
          return replace;
        } else {
          const stream = new Readable();
          stream._read = function(size) {
            if (typeof replace === 'string' || Buffer.isBuffer(replace)) {
              this.push(replace);
            }
            this.push(null);
          };
          return stream;
        }
      },
      on: function(eventName, callback) {
      },
      send: function(callback) {
      }
    };

    // different locations for the paramValidation property
    const config = (client.config || client.options || _AWS.config);
    if (config.paramValidation) {
      try {
        // different strategies to find method, depending on wether the service is nested/unnested
        const inputRules =
          ((client.api && client.api.operations[method]) || client[method] || {}).input;
        if (inputRules) {
          const params = userArgs[(userArgs.length || 1) - 1];
          new _AWS.ParamValidator((client.config || _AWS.config).paramValidation).validate(inputRules, params);
        }
      } catch (e) {
        callback(e, null);
        return request;
      }
    }

    // If the value of 'replace' is a function we call it with the arguments.
    if (typeof replace === 'function') {
      const result = replace.apply(replace, userArgs.concat([callback]));
      if (storedResult === undefined && result != null &&
          typeof result.then === 'function') {
        storedResult = result
      }
    }
    // Else we call the callback with the value of 'replace'.
    else {
      callback(null, replace);
    }
    return request;
  });
}