How can I write a test for such situation?

[DavidHe1127]

I am not sure this is a correct place to ask a question. But I see git issues tab is really active and hope someone can help me out ASAP.

category.js to be tested

'use strict';

module.exports = (client) => {
  const filter = (done) => {
    client.getEntries({
      content_type: 'category',
      select: 'fields'
    }).then(res => {
      const categories = res.items.map((x) => {
        return {
          id: x.sys.id,
          name: x.fields.name
        };
      });
      done(null, categories);
    }).catch(err => {
      console.log(err);
      done(err, null);
    });
  };

  return {
    filter
  };
};

My current test - client is an instance created from a constructor provided by 3rd library.

'use strict'

const test = require('tap').test;
const td = require('testdouble');
const fs = require('fs');
const category = require('../category');

const setup = () => {
  return JSON.parse(fs.readFileSync(`${__dirname}/entries.sample.json`, 'utf-8'));
};

test('get all categories', (t) => {
  const content = setup();
  let client = {
    getEntires: () => {
      return content;
    }
  };
  client = td.object(client);
  const _category = category(client);
  const filter =  _category.filter;
  // client.getEntires = function() {
  //   return content;
  // };
  const _filter = td.function('filter');
  td.when(_filter).thenCallback(null, {
    id: 'xxx',
    name: 'yyy'
  });
  // td.verify(_done(content));
  // const _category = category(client);
  // td.when(client.getEntires()).thenCallback(null, {
  //   id: 'xxx',
  //   name: 'xxx'
  // });
  // _category.filter(_done);
  t.end();
});

My question is as follow

How do I test the case that given the response from client.getEntries promise resolve callback, the callback function done is executed with second argument filled up with correct value like {id: 'xxx', name: 'yyyy'}

Also, is my design too difficult to write a test?

Many thanks in advance.

[searls]

You could do something like this to cover both cases:

it('is happy', function(done) {
  var client = td.object(['getEntries'])
  td.when(client.getEntries({
    content_type: 'category', 
    select: 'fields'
  })).thenResolve({items: [{sys: {id: 'lolid'}, {fields: {name: 'lolname'}}}]})

  subject(client).filter(function(er, result) {
    expect(er).toBeFalsy()
    expect(result).toEqual([{id: 'lolid', name: 'lolname'}])
    done()
  })
})

it('is sad', function(done) {
  var client = td.object(['getEntries'])
  td.when(client.getEntries({
    content_type: 'category', 
    select: 'fields'
  })).thenReject('lolerror')

  subject(client).filter(function(er, result) {
    expect(result).toBeFalsy()
    expect(er).toEqual('lolerror')
    done()
  })
})