I am trying to write a unit test for the class in the example below.
const DependencyClass = require('../../../../Dependency/src/index').DependencyClass;
const string = 'test';
class FirstClass {
async getResult() {
const dependency = new DependencyClass();
const result = dependency.getResult(string);
return result;
}
}
module.exports = {
FirstClass
};
I am trying to stub the getResult() method of the DependencyClass class so it returns a predefined value when called from my unit tests but cant figure out how to do it.
const FirstClass = require('../../lib/FirstClass ').FirstClass;
describe('FirstClass.js', function() {
describe('getResult()', function() {
it('throws an exception if the result is not returned', async function() {
const firstClass = new FirstClass();
sinon.replace(firstClass.getResult, 'DependencyClass.getResult', function() {
const fakeResult =
[
'test1',
'test2'
];
return fakeResult;
});
const expectedResult =
[
'test1',
'test2'
];
const result = await firstClass.getResult();
expect(result).to.deep.eq(expectedResult);
});
});
});
afterEach(function() {
sinon.restore();
});
I understand that DependencyClass.getResult is not a property of the firstClass.getResult object but I am struggling to understand how sinon should be used in this context.
If you want to stub method getResult() from class DependencyClass, then you need to create stub from it: sinon.stub(DependencyClass.prototype, 'getResult');.
Here the complete example.
Note: I remove all async await, because it is unnecessary for this simple example.
File DependencyClass.js
// #file DependencyClass.js
class DependencyClass {
getResult() {
return 'xxx';
}
}
module.exports = { DependencyClass };
File FirstClass.js
// #file FirstClass.js
const { DependencyClass } = require('./DependencyClass.js');
const string = 'test';
class FirstClass {
getResult() {
const dependency = new DependencyClass();
return dependency.getResult(string);
}
}
module.exports = { FirstClass };
Test spec file
// #file stackoverflow.spec.js
const sinon = require('sinon');
const { expect } = require('chai');
const { DependencyClass } = require('./DependencyClass');
const { FirstClass } = require('./FirstClass');
describe('FirstClass.js', function () {
describe('getResult()', function () {
it('throws an exception if the result is not returned', function () {
// Create fake response.
const fakeResult = ['test1', 'test2'];
// Create stub DependencyClass method getResult().
const stubDependencyGetResult = sinon.stub(DependencyClass.prototype, 'getResult');
stubDependencyGetResult.returns(fakeResult);
// Initiate first class.
const firstClass = new FirstClass();
// Call firstClass method getResult.
const result = firstClass.getResult();
// Check whether the result is correct.
expect(result).to.deep.equal(fakeResult);
// Verify stub get called.
expect(stubDependencyGetResult.calledOnce).to.equal(true);
// Restore stub.
stubDependencyGetResult.restore();
});
});
});
When I run it using mocha:
$ mocha stackoverflow.spec.js
FirstClass.js
getResult()
✓ throws an exception if the result is not returned
1 passing (6ms)
$
Hope this helps.
Related
This is the function I am testing (stripped down for simplicity's sake):
populate.js->
const { createSessionID } = require('./populate-template-utilities');
const createFile = async () => {
const responseHeader = {};
responseHeader.SessionID = createSessionID();
return responseHeader;
};
module.exports = {
createFile,
};
The function this function calls:
populate-template-utilities ->
const createSessionID = () => {
const digits = (Math.floor(Math.random() * 9000000000) + 1000000000).toString();
return `PAX${digits}`;
};
module.exports = {
createSessionID,
};
And my unit test (again stripped down):
const { createSessionID } = require('../app/lib/populate-template-utilities');
describe('create XML for output files', () => {
const mockID = jest
.spyOn(createSessionID)
.mockImplementation(() => 'PAX123456');
it('should create a PAX File', async () => {
const result = await createFile();
expect(result).toEqual(getFile);
});
});
I want createSessionID to return 'PAX123456' and think mockID should do it, but it's erroring with:
Cannot spy the undefined property because it is not a function; undefined given instead
The spyOn method needs at least two parameters: object and methodName.
Try sth like this:
import * as populateTemplateUtils from "../sessionStuff";
import { createFile } from "../createFile";
describe('create XML for output files', () => {
it('should create a PAX File', async () => {
jest
.spyOn(populateTemplateUtils, 'createSessionID')
.mockReturnValue('PAX123456');
const result = await createFile();
expect(result).toEqual({"SessionID": "PAX123456"});
});
});
It all started to work when I changed the:
module.exports = {
createSessionID,
};
to:
export const createSessionID = () => {
I'm unit testing a method in fileA.js that requires a new class instance from fileB.js with success.
The problem is that I get success, as expected but this specific test hangs and I don't get results from istanbul.
Yes, I have already added --exit flag. This only happens if I run this test... Why does it hang?
This is the method in fileA.js:
global.mapperObj = {};
const opts = config.opts
(...)
async function startServices() {
const data = await getData();
Object.keys(data).forEach(function(key) {
mapperObj[key] = new ClassInFileB(key, data[key], opts);
mapperArray.push(key);
});
}
The class in fileB.js:
const npmPool = require('npmPackage');
class ClassInFileB{
constructor(ip, port, opts) {
this.classPool = npmPool.createPool(ip, port, opts);
}
(...)
// other class methods
}
And the test for that method:
const rewire = require('rewire');
const fileA = rewire(`path/to/fileA`);
const ClassInFileB = require(`path/to/fileB`);
describe('Testing startServices() function', function () {
it('It should not throw errors', async function () {
let result;
let error = false;
global.mapperArray = [];
try {
function getDataMock() {
return { '0.0.0.1': 'thisIsSomething'};
}
fileA.__set__('getData', getDataMock);
// Create a stub instance to ClassInFileB class avoiding the constructor
sinon.createStubInstance(ClassInFileB);
result = await fileA.startServices();
} catch (err) {
error = err;
}
expect(error).to.be.false;
});
I have the following method:
import { ObjectDal } from "./ObjectDal";
export class ObjectBL {
async getObject(id) {
try {
let dal = new ObjectDal();
let result = await dal.get(id);
return result;
} catch (err) {
// log the error
}
}
where the ObjectDal class is:
export class ObjectDal {
async get(id) {
// open connection to db
// make a query based on id
// put the result in a `result` variable
return result;
}
}
I have to write an unit test for the getObject() method using only Mocha...
This is the begining of the UT:
const assert = require('assert');
const ObjectBL = require("../ObjectBL");
describe('Something', () => {
describe('...', () => {
it('getObject_GetsObjectUsingID_True', async () => {
// arange
let id = "123456789101";
let expected = {
"name": "ana",
"hasApples": true
};
let test = new ObjectBL.ObjectBL();
let result = await test.getObject(id);
assert.deepStrictEqual(result, expected);
});
});
});
But in this case I would have to call the method from the ObjectDal class...
How can I mock the call to the get() method using only Mocha?
I found answers with Sinon, or Mocha with Sinon and/or Chai... but nothing with only Mocha...
Proxies might be the way to go for you.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy
You could mok methods by using a Proxy like so:
const assert = require('assert');
const ObjectBL = require("../ObjectBL");
describe('Something', () => {
describe('...', () => {
it('getObject_GetsObjectUsingID_True', async () => {
// arange
let id = "123456789101";
let expected = {
"name": "ana",
"hasApples": true
};
let test = new ObjectBL.ObjectBL();
const handler = {
get: function(obj, prop) {
// mok the getObject method
if(prop === 'getObject'){
return () => {
return Promise.resolve({
"name": "ana",
"hasApples": true
});
}
} else {
return obj[prop];
}
}
};
const p = new Proxy(test, handler);
let result = await p.getObject(id);
assert.deepStrictEqual(result, expected);
});
});
});
If you ONLY want to mok the ObjectDal.get method, you might want to override the prototype and recover it afterwards:
const assert = require('assert');
const ObjectBL = require("../ObjectBL");
const ObjectDal = require("../ObjectDal");
describe('Something', () => {
describe('...', () => {
it('getObject_GetsObjectUsingID_True', async () => {
// arange
let id = "123456789101";
let expected = {
"name": "ana",
"hasApples": true,
};
const proto = Object.getOwnPropertyDescriptor(ObjectDal, 'prototype').value;
const backup = proto.get;
proto.get = () => {
return Promise.resolve({
"name": "ana",
"hasApples": true,
});
}
let test = new ObjectBL.ObjectBL();
let result = await test.getObject(id);
ObjectDal.prototype.get = backup;
assert.deepStrictEqual(result, expected);
});
});
});
You could also override the ObjectDal with a Proxy and implement the construct handler to return a dummy ObjectDal, but this might be more tricky, since you are working with modules.
Testing is feedback, not just on whether or not your code works as advertised but even more crucially on the quality of your design.
The fact that you are having trouble writing the tests is your first sign you did something sub-optimal in the implementation. What you want is this:
export class ObjectBL {
constructor (dal) {
this.dal = dal;
}
async getObject(id) {
try {
let result = await this.dal.get(id);
return result;
} catch (err) {
// log the error
}
}
...and now the dependency is clear rather than implicit and will show up in editor tooltips, is more amenable to static analysis, etc. And it solves your problem: now you can mock it easily for testing, no further libraries needed.
What would be the unit test which would fake the calls to callActivity in the orchestrator below to return a known value and to expect that the orchestrator returns that value.
The examples on the azure durable functions documentation for unit testing[1] are all written in C# and I've not been able to replicate
them in javascript despite several attempts. This is because I don't know how to construct an orchestrator with a fake context.
const df = require('durable-functions');
module.exports = df.orchestrator(function* orchestratorFunctionGenerator(context) {
const input = context.df.getInput();
const apimApiName = input.apimApiName;
const indexNames = yield context.df.callActivity('GetIndexNames', apimApiName);
const indexerName = indexNames.idle;
const indexerStatus = yield context.df.callActivity('GetIndexerStatus', indexerName);
return indexerStatus;
});
[1] https://learn.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-unit-testing
The approach we went with was to extract the generator method out into it's own module.
module.exports = function* orchestratorFunctionGenerator(context) {
const input = context.df.getInput();
const apimApiName = input.apimApiName;
const indexNames = yield context.df.callActivity('GetIndexNames', apimApiName);
const indexerName = indexNames.idle;
const indexerStatus = yield context.df.callActivity('GetIndexerStatus', indexerName);
return indexerStatus;
};
then require it
const df = require('durable-functions');
const generatorFunction = require('./generator-function');
module.exports = df.orchestrator(generatorFunction);
and then test the function in isolation
const chai = require('chai');
const sinon = require('sinon');
const getIndexerStatusOrchestratorGenerator = require('../../GetIndexerStatusOrchestrator/generator-function');
const expect = chai.expect;
function iterateGenerator(generator) {
let result = generator.next();
while (!result.done) {
result = generator.next(result.value);
}
return result;
}
describe('getIndexerStatusOrchestrator', () => {
it('happy path should return \'inProgress\'', () => {
const indexNames = { active: 'index-1', idle: 'index-2' };
const apimApiName = 'api';
const input = { apimApiName };
const stubCallActivity = sinon.stub();
stubCallActivity.withArgs('GetIndexNames', apimApiName).returns(indexNames);
stubCallActivity.withArgs('GetIndexerStatus', indexNames.idle).returns('inProgress');
const context = {
df: {
callActivity: stubCallActivity,
getInput: sinon.fake.returns(input),
},
};
const generator = getIndexerStatusOrchestratorGenerator(context);
const result = iterateGenerator(generator);
expect(result.value).to.equal('inProgress');
});
it('indexer status should be for the idle index', () => {
const indexNames = { active: 'index-1', idle: 'index-2' };
const apimIndexName = 'api';
const input = { apimApiName: apimIndexName };
const stubCallActivity = sinon.stub();
stubCallActivity.withArgs('GetIndexNames', apimIndexName).returns(indexNames);
stubCallActivity.withArgs('GetIndexerStatus', indexNames.idle);
// use stub as a mock since we need both stub and mock behaviour
// for 'callActivity' and this was the easier option
stubCallActivity.withArgs('GetIndexerStatus').callsFake((method, indexerName) => {
expect.fail(`Unexpected indexer name ${indexerName}`);
});
const context = {
df: {
callActivity: stubCallActivity,
getInput: sinon.fake.returns(input),
},
};
const generator = getIndexerStatusOrchestratorGenerator(context);
iterateGenerator(generator);
// expectations set above
});
});
As might be expected this a trivial example of an orchestrator. We have orchestrators which have considerably more logic in them and where the tests will have more value.
In addition, I personally would not use the mocking approach in the 2nd test and would just rely on testing the outputs using stubs to fake dependency interactions.
I need to assert whether a constructor was called using sinon. Below is how I can create a spy.
let nodeStub: any;
nodeStub = this.createStubInstance("node");
But how can I verify that this constructor was called with the relevant parameters? Below is how the constructor is actually called.
node = new node("test",2);
Any help would be much appreciated.
Below is the code I have.
import {Node} from 'node-sdk-js-browser';
export class MessageBroker {
private node: Node;
constructor(url: string, connectionParams: IConnectionParams) {
this.node = new Node(url, this.mqttOptions, this.messageReceivedCallBack);
}
}
Given the following code myClient.js:
const Foo = require('Foo');
module.exports = {
doIt: () => {
const f = new Foo("bar");
f.doSomething();
}
}
You can write a test like this:
const sandbox = sinon.sandbox.create();
const fooStub = {
doSomething: sandbox.spy(),
}
const constructorStub = sandbox.stub().returns(fooStub);
const FooInitializer = sandbox.stub({}, 'constructor').callsFake(constructorStub);
// I use proxyquire to mock dependencies. Substitute in whatever you use here.
const client2 = proxyquire('./myClient', {
'Foo': FooInitializer,
});
client2.doIt();
assert(constructorStub.calledWith("bar"));
assert(fooStub.doSomething.called);
//module.js
var Node = require('node-sdk-js-browser').Node;
function MessageBroker(url) {
this.node = new Node(url, 'foo', 'bar');
}
module.exports.MessageBroker = MessageBroker;
//module.test.js
var sinon = require('sinon');
var rewire = require('rewire');
var myModule = require('./module');
var MessageBroker = myModule.MessageBroker;
require('should');
require('should-sinon');
describe('module.test', function () {
describe('MessageBroker', function () {
it('constructor', function () {
var spy = sinon.spy();
var nodeSdkMock = {
Node: spy
};
var revert = myModule.__set__('node-sdk-js-browser', nodeSdkMock);
new MessageBroker('url');
spy.should.be.calledWith('url', 'foo', 'bar');
revert();
});
});
});