Why am I getting "Error: Resolution method is overspecified"?
node.jsmocha.jsnode.js Problem Overview
After the upgrade, Mocha can not even run a simple test here is the code
const assert = require('assert');
it('should complete this test', function (done) {
return new Promise(function (resolve) {
assert.ok(true);
resolve();
})
.then(done);
});
I took this code from [here][1]
I understood that it now throws an exception Error: Resolution method is overspecified. Specify a callback * or * return a Promise; not both.
But how to make it work? I did not understand. I have
node -v 6.9.4
mocha -v 3.2.0
How to run this code are now in a new and correct format? [1]: https://github.com/mochajs/mocha/blob/master/CHANGELOG.md#boom-breaking-changes
node.js Solutions
Solution 1 - node.js
Just drop
.then(done);
and replace function(done)
with function()
You are returning a Promise so calling done is redundant as it said in error message
In the elder versions you had to use callback in case of async methods like that
it ('returns async', function(done) {
callAsync()
.then(function(result) {
assert.ok(result);
done();
});
})
Now you have an alternative of returning a Promise
it ('returns async', function() {
return new Promise(function (resolve) {
callAsync()
.then(function(result) {
assert.ok(result);
resolve();
});
});
})
But using both is misleading (see for example here https://github.com/mochajs/mocha/issues/2407)
Solution 2 - node.js
Mocha allows to either use a callback:
it('should complete this test', function (done) {
new Promise(function (resolve) {
assert.ok(true);
resolve();
})
.then(done);
});
OR return a promise:
it('should complete this test', function () {
return new Promise(function (resolve) {
assert.ok(true);
resolve();
});
});
// Or in the async manner
it('should complete this test', async () => {
await Promise.resolve();
assert.ok(true);
});
You can't do both.
Solution 3 - node.js
I had to removed the done
from the function parameter and the done()
of the function call
Before
before(async function (done) {
user = new User({ ...});
await user.save();
done()
});
After
before(async function () {
user = new User({ ...});
await user.save();
});
These works for me
Solution 4 - node.js
I had this same issue. A lot of times Mocha is paired with another library called Chai. Chai has a package called "chai-as-promised". It gives you the super simple ability to write less code and test promises. In your case of just testing if a promise resolves, it seems perfect.
const chai = require('chai');
const chaiAsPromised = require("chai-as-promised");
const should = require("chai").should();
chai.use(chaiAsPromised);
describe("Testing with correct syntax and non repeated names", () => {
it("Should give us a positive response", () => {
graphQL.sendToGQL(model,"specialEndpoint").should.eventually.be.an("Object");
})
})
Solution 5 - node.js
An example of async functions with done breaking.
Failure Case
it('If the credentials exists in the system it should return the token generated against it.', async (done) => {
let aObj = await admin.createAdmin();
chai.request(server)
.post("/authenticate")
.set("Content-Type", "application/x-www-form-urlencoded")
.send({username: aObj.login,password:aObj.password})
.end((err, res) => {
res.should.have.status(200);
res.body.should.be.a("string");
done();
});
});
Success Case
it('If the credentials exists in the system it should return the token generated against it.', async () => {
let adminObj = await admin.createAdmin();
chai.request(server)
.post("/auth/login")
.set("Content-Type", "application/x-www-form-urlencoded")
.send({username: adminObj.login,password:adminObj.password})
.end((err, res) => {
res.should.have.status(200);
res.body.should.be.a("string");
// done();
});
});
Solution 6 - node.js
If you don't have callbacks, prior answers (which suggest deleting the done
) is correct.
If need to both await some external promise, and then exercise a callback/errback-based implementation in your test, that solution doesn't help you.
You can use a library like pify
to convert the callback API to use promises.
Alternatively, you can use a Latch
in your callback:
it("test", async () => {
const l = new Latch()
const v = await promiseValue()
s.methodThatTakesCallback((err, result) => {
expect(result).to.eql(expected)
l.resolve() // < notifies mocha your test is done
})
return l.promise
})
In TypeScript, here's a very stripped-down Latch implementation:
/**
* Simple one-count concurrent barrier
*/
export class Latch {
readonly promise: Promise<void>
resolve!: () => void
constructor() {
this.promise = new Promise<void>(resolve => (this.resolve = resolve))
}
}
Solution 7 - node.js
Just emit done callback completely and use async instead. (This implementation is based on an express api running on firebase functions, using a custom jsonwebtoken)
const { FIREBASE_UID } = require('dotenv').config()?.parsed
const chai = require('chai');
const chaiHttp = require('chai-http');
const server = require('../lib/api').API;
const should = chai.should();
const expect = chai.expect
chai.use(chaiHttp)
const test = chai.request(server).keepOpen()
// get your token with an earlier mock request and store to a var
describe('Just checking a token', () => {
let some_token
it('should print custom jwt for testing, status: 200'), async () => {
try {
const res = await test.get(`/createCustomFirebaseToken/${FIREBASE_UID}`).send()
res.should.exist
res.should.have.status(200);
res.should.have.json
some_token = (JSON.parse(res.text)).token
} catch (error) {
throw error
}
}
it('should print details:PING, status:200'), async () => {
try {
const res = await test.get('/').set('Authorization',`Bearer ${some_token}`)
.send()
res.should.exist
res.should.have.status(200);
res.should.have.json
const { details, status } = JSON.parse(res.text)
expect(details).to.equal('PING')
expect(status).to.equal(200)
} catch (error) {
throw error
}
}
after(() => test.close())
})