promiseloop

This package was developed to resolve testing issues with nested promises and timing mocks but can be used elsewhere as well - it is kind of generous.

With this module you can test something on each level of Promise.then with multiple promises run simultanousely.

It can be used to check something on each level of then method. then method is executed in most cases with setImmediate or process.nextTick so it is hard to test future "ticks" in synchronous way for example setTimeout inside then will not be catched by timer mocks because setTimeout inside then will be fired in the future (ticks). promiseloop is going through all levels of ticks and can catch all those setTimouts or other things that are executed in next (future) ticks.

Here you can read about the problem: http://stackoverflow.com/questions/42446795/how-to-use-jasmine-clock-settimeout-in-nested-promises-when-order-matters-ja

usage

npm install promiseloop


let promiseLoop = require('promiseloop')(Promise);
// where Promise is your Promise implementation

let levelsDeep = 10; // how deep we want to go through 'then' levels?
function iterationFn(){
  // this function will be executed in each level of 'then'
  // each level of 'then' is in most cases something like setImmediate or nextTick
}
function finalFn(){
  // this function will be executed at the end of the chain - final
}
promiseLoop(levelsDeep,iterationFn,finalFn);

we can only have finalFn instead of iteration

let levelsDeep = 10; // how deep we want to go through 'then' levels?
function finalFn(){
  // this function will be executed at the end of the chain - final
}
promiseLoop(levelsDeep,finalFn);

For example if you need to test multiple promises and you does not want to make sophisticated algorithm to check that everything is already executed on each level.

let testNr=0;
 
new Promise((resolve,reject)=>{
  resolve("ok");
}).then(()=>{
  // level 1
  testNr++; // 1
}).then(()=>{
  // level 2
  testNr++; // 3
});
 
new Promise((resolve,reject)=>{
  resolve("ok");
}).then(()=>{
  // level 1
  testNr++; // 2
}).then(()=>{
  // level 2
  testNr++; // 4
});
 
function each(currentLevel){
  if(currentLevel==1){
    expect(testNr).toEqual(2);
  }else if(currentLevel==2){
    expect(testNr).toEqual(4);
  }
}
function final(){
  expect(testNr).toEqual(4);
  done();
}
promiseLoop(3,each,final);