Bypass Ajax request within javascript promise in Unit Testing - ajax

Question

I have a function called getStudentData(),returns resolved data.
Inside getStudentData(), I have an Ajax request.
I want to Bypass Ajax request in my unit test case using Mocha , so that when i make a call to getStudentData(), the data should be returned.
Please find the code below:
getStudentData: function() {
return studentData || (studentData = new Promise(function(resolve, reject) {
var request = {
//request data goes here
};
var url = "/student";
$.ajax({
url: url,
type: "POST",
data: JSON.stringify(request),
dataType: "json",
contentType: "application/json",
success: function(response, status, transport) {
//success data goes here
},
error: function(status, textStatus, errorThrown) {
reject(status);
}
});
}).then(function(data) {
return data;
})['catch'](function(error) {
throw error;
}));
}
Please let me know how to Bypass Ajax request By stubbing data using sinon.js .so that when i make a call to getStudentData() , data should be returned.

Answer 1

First of all doing:
then(function(data){ return data; })
Is a no-op. So is:
catch(function(err){ throw err; });
Now, your code uses the explicit construction anti-pattern which is also a shame, it can be minimized to:
getStudentData: function() {
var request = {
//request data goes here
};
var url = "/student";
return studentData ||
(studentData = Promise.resolve($.ajax({
url: url,
type: "POST",
data: JSON.stringify(request),
dataType: "json",
contentType: "application/json" })));
}
Now, that we're over that, let's talk about how you'd stub it. I'd do:
myObject.getStudentData = function() {
return Promise.resolve({}); // resolve with whatever data you want to test
};
Which would let you write tests that look like:
it("does something with data", function() { // note - no `done`
// note the `return` for promises:
return myObj.getStudentData().then(function(data){
// data available here, no ajax request made
});
});
Although in practice you'll test other objects that call that method and not the method itself.