通过 Tedious with Jest 测试连接到 SQL 服务器的 NodeJS function，抛出错误：无法重新定义属性：连接

Question

Trying to test a Tedious connector function with Jest.

In code-file db_server.js I have this function below, it works as expected.

const AWS = require('aws-sdk')
const tedious = require('tedious')
const Request = require('tedious').Request;
const Connection = require('tedious').Connection;

exports.execSQLCmd = async function (conn_store, cmd) {
let config = await exports.getParameter(conn_store)
let conn_cfg = JSON.parse(config)

//connect
const connection = new Connection(conn_cfg);
connection.on('connect', function (err) {
    if (err) {
        console.log('CONNECTION ERROR: ' + err);
    }

    console.log('CONNECTED TO: ' + conn_cfg.server);
    executeStatement();
});
connection.connect();

//execute the sql command   
let result = '';
function executeStatement() {
    let request = new Request(cmd, function (err) {
        if (err) {
            console.log('REQUEST ERROR: ' + err);
        }
    });
    //add three event hooks to the request
    request.on('row', function (columns) {
        columns.forEach(function (column) {
            result += (column.value === null ? '' : column.value) + ',';
        });
        result = result.replace(/,$/, '\r\n')
    });
    request.on('done', function (rowCount, more) {
        console.log('SQL COMMAND COMPLETED: ' + rowCount + ' rows returned');
    });
    request.on('requestCompleted', function (rowCount, more) {
        connection.close();
        console.log('CONNECTION TO SERVER CLOSED');
    });

    connection.execSql(request);
}

return result;

}

exports.Request = Request
exports.Connection = Connection
exports.tedious = tedious

In the test file index.spec.js , I have the following test:

describe('Test execSQLCmd', () => {
const server = require("../src/db_server.js")

afterEach(() => {
  jest.restoreAllMocks();
});
    


test('should query sql', async () => {
server.getParameter = jest.fn().mockReturnValue('{"xxx":123,"yyy":"hello"}') 
server.execSQLCmd = jest.fn().mockReturnThis()
const TedConnect = jest.spyOn(server.tedious, 'Connection').mockReturnValue(jest.fn(() => ({
             connect: () => {},
             on: (connect, cb) => cb(),
             close: () => {},
             execSql: () => {}
  })));

  const TedRequest = jest.spyOn(server.tedious, 'Request').mockReturnValue(jest.fn(() => ({
              constructor: (sqlString, cb) => cb('err', null, null),
              on: [
                    (row, cb)=> cb('columns'),
                    (done, cb)=> cb('rowCount', 'more'),
                    (requestCompleted, cb) => cb('rowCount', 'more')
                  ]
  })));
  
  let exec = server.execSQLCmd("/pstore/name", "select 1")
  expect(TedConnect).toBeCalledTimes(1)
  expect(TedRequest).toBeCalledTimes(1)
  

})


})

When I try to run the test, I get this error:

Test execSQLCmd › should query sql

TypeError: Cannot redefine property: Connection
    at Function.defineProperty (<anonymous>)

  298 |     server.getParameter = jest.fn().mockReturnValue('{"xxx":123,"yyy":"hello"}')
  299 |     server.execSQLCmd = jest.fn().mockReturnThis()
> 300 |     const TedConnect = jest.spyOn(server.tedious, 'Connection').mockReturnValue(jest.fn(() => ({
      |                             ^
  301 |                  connect: () => {},
  302 |                  on: (connect, cb) => cb(),
  303 |                  close: () => {},

  at ModuleMockerClass.spyOn (node_modules/jest-mock/build/index.js:826:16)
  at Object.<anonymous> (__tests__/index.spec.js:300:29)

  Test Suites: 1 failed, 1 total

"tedious": "^14.1.0"
"jest": "^26.6.3",

I'm not seeing why this test fails.

Any help appreciated, thanks!

EDIT

Above error not happening after the fiollowing Test changes:

test('should query sql', async () => {
    server.getParameter = jest.fn().mockReturnValue('{"xxx":123,"yyy":"hello"}') 
    server.execSQLCmd = jest.fn().mockReturnThis()
    server.Connection = jest.fn().mockReturnValue(jest.fn(() => ({
  connect: () => {},
  on: (connect, cb) => cb(),
  close: () => {},
  execSql: () => {}
}))) 

server.Request = jest.fn().mockReturnValue(jest.fn(() => ({
  constructor: (sqlString, cb) => cb('err', null, null),
  //addParameter: (name, type, value) => {},
  on: [
        (row, cb)=> cb('columns'),
        (done, cb)=> cb('rowCount', 'more'),
        (requestCompleted, cb) => cb('rowCount', 'more')
      ]
  }))) 

  let exec = server.execSQLCmd("/pstore/name", "select 1")
  expect(server.Connection).toBeCalledTimes(1)
  expect(server.Request).toBeCalledTimes(1)

 })

However, now server.execSQLCmd does't run, I cannot step into it with debug, exists right away and returns a large mock object.

Anyone see what I'm doing wrong here?

Thanks!

Answer 1

exports.execSQLCmd = async function (conn_store, cmd) {
    
    let config = await exports.getParameter(conn_store)
    let conn_cfg = JSON.parse(config)

    //connect
    exports.connect_exec(conn_cfg, cmd);    

    return result;
}

function connect_exec(conn_cfg, cmd) {
    const connection = exports.get_connection(conn_cfg);
    exports.on_connect(connection, cmd);
    connection.connect();
    return connection;
}

function on_connect(connection, cmd) {
    connection.on('connect', function (err) {
        if (err) {
            console.log('CONNECTION ERROR: ' + err);
        }
        console.log('CONNECTED');
        exports.execute_statement(connection, cmd);
    });
}

function get_connection(conn_cfg) {
    return new Connection(conn_cfg);
}

function execute_statement(connection, cmd) {
    let request = exports.get_request(connection, cmd);

    connection.execSql(request);
}

function get_request(connection, cmd) {
    let request = new Request(cmd, function (err) {
        if (err) {
            console.log('REQUEST ERROR: ' + err);
        }
    });
    //add three event hooks to the request
    request.on('row', function (columns) {
        columns.forEach(function (column) {
            result += (column.value === null ? '' : column.value) + ',';
        });
        result = result.replace(/,$/, '\r\n');
    });
    request.on('done', function (rowCount, more) {
        console.log('SQL COMMAND COMPLETED: ' + rowCount + ' rows returned');
    });
    request.on('requestCompleted', function (rowCount, more) {
        connection.close();
        console.log('CONNECTION TO SERVER CLOSED');
    });
    return request;
}

exports.AWS = AWS;

exports.connect_exec = connect_exec
exports.execute_statement = execute_statement
exports.get_request = get_request
exports.get_connection = get_connection
exports.on_connect = on_connect

Here's my test:

describe('Test execSQLCmd', async () => {
    const server = require("../src/opportunity/db_server.js")
     
      afterEach(() => {
      jest.restoreAllMocks();
    });

   test('should query sql', async () => {
    server.getParameter = jest.fn().mockReturnValue('{"xxx":123,"yyy":"hello"}') 
    
    server.get_connection = jest.fn().mockReturnValue({
      connect: () => {},
      on: (connect, cb) => cb(),
      close: () => {} ,
      execSql: () => {}
    }) 

    server.get_request = jest.fn().mockReturnValue({
      constructor: (sqlString, cb) => cb('err', null, null),
      on: [
            (row, cb)=> cb('columns'),
            (done, cb)=> cb('rowCount', 'more'),
            (requestCompleted, cb) => cb('rowCount', 'more')
          ]
      })
    
      await server.execSQLCmd("/pstore/name", "select 1")      
      expect(server.get_connection).toHaveBeenCalled()
      expect(server.get_request).toHaveBeenCalled()
   })
}) 

Took me a day to write all the code for main functionality, ore than there is here.

Took me 2.5 days to figure out just this test. Silly!