I have a function for which I am writing unit test but that function is calling another function and there I am not able to mock/stub that function.
for example :
function getValue( param1, param2, callback){
getData(param1, param3).then( response) => {
return callback();
}, (err) => {
return callback();
});
}
So I don't know how to mock getData() function.
Here is a working example that demonstrates what you are trying to do:
lib.js
function getData(param1, param2) {
return fetch('someUrl'); // <= something that returns a Promise
}
exports.getData = getData;
code.js
const lib = require('./lib');
export function getValue(param1, param2, callback) {
return lib.getData(param1, param2).then(response => {
callback(response);
}).catch(err => {
callback(err);
});
}
exports.getValue = getValue;
code.test.js
const sinon = require('sinon');
const lib = require('./lib');
const { getValue } = require('./code');
describe('getValue', () => {
it('should do something', async () => {
const stub = sinon.stub(lib, 'getData');
stub.resolves('mocked response');
const callback = sinon.spy();
await getValue('val1', 'val2', callback);
sinon.assert.calledWithExactly(stub, 'val1', 'val2'); // Success!
sinon.assert.calledWithExactly(callback, 'mocked response'); // Success!
});
});
Update
OP added in the comments that they can't use async / await and are exporting the function using module.exports = getData;.
In that case the module export is the function and the entire module needs to be mocked with something like proxyquire.
The assertions should be done in a then callback and the test should return the resulting Promise so mocha knows to wait for it to resolve.
Updated example:
lib.js
function getData(param1, param2) {
return fetch('someUrl'); // <= something that returns a Promise
}
module.exports = getData;
code.js
const getData = require('./lib');
function getValue(param1, param2, callback) {
return getData(param1, param2).then(response => {
callback(response);
}).catch(err => {
callback(err);
});
}
module.exports = getValue;
code.test.js
const sinon = require('sinon');
const proxyquire = require('proxyquire');
describe('getValue', () => {
it('should do something', () => {
const stub = sinon.stub();
stub.resolves('mocked response');
const getValue = proxyquire('./code', { './lib': stub });
const callback = sinon.spy();
return getValue('val1', 'val2', callback).then(() => {
sinon.assert.calledWithExactly(stub, 'val1', 'val2'); // Success!
sinon.assert.calledWithExactly(callback, 'mocked response'); // Success!
});
});
});
module.exports = getData also async() is not working in node js 6 and as of now it is throwing following error TypeError: Cannot stub non-existent own property getData. Please respond . Thanks
TypeError: Cannot read property 'then' of undefined this what I am getting. Also actual function is being called.function getValue( param1, param2, callback){
getData(param1, param3).then( response) => {
callback(response);
});
}
getvalue(param1, param2, function(error, response)) {
console.log(response)
}
It might help you.
getDatadefined ?getDatais defined in some other file which I am importing.getDataeven if it is a random function in the same file, but it must be exported and it must be called using the module export. (See this answer for an ES6 version, a Node.js module would exportgetDatalike this:exports.getData = getData;and then call it withingetValuelike this:exports.getData(...))