CODEWITHSUNDEEP
javascriptunit-testingjasmine
davy
davy

Reputation: 4562

Can we perform async operations within a test using Jasmine?

I am learning testing with Jasmine and I'm looking for a bit of clarification on async testing to further my understanding.

In the following code, the test in the first spec works but the second version where I've removed the beforeEach and moved the async calls into the it does not.

describe("Working Asnc", function() {
 var value = 0;

 function funcRunInBackground() {
   value = 1;
};  

 function wrapFuncRunInBackground(done) {  
    setTimeout(function() {
       funcRunInBackground();
       done();
    }, 2000);       
 }    

 beforeEach(function(done) {
     wrapFuncRunInBackground(done);          
 });                 

 it("should be greater than 0", function() {
   expect(value).toBeGreaterThan(0);
 });

});

describe("Not working Asnc", function() { var value = 0;

 function funcRunInBackground() {
   value = 1;
 };  

 function wrapFuncRunInBackground(done) {  
   setTimeout(function() {
       funcRunInBackground();
       done();
   }, 2000);       
 }                 

 it("should be greater than 0", function(done) {
   wrapFuncRunInBackground(done);       
   expect(value).toBeGreaterThan(0);
 });

});

code pen here

Can we do the asnc operation from with the test itself if this is ever required?

Upvotes: 0

Views: 52

Answers (2)

Vladimir G.
Vladimir G.

Reputation: 885

You can not syncronize js async code that way. You just can not wait for async code would be executed without using zallbacks/promises/co+generators/etc. In your case it should be something like:

it("should be greater than 0", function(done) {
   wrapFuncRunInBackground(function(){
       expect(value).toBeGreaterThan(0);
       done();
   });       
 });

Upvotes: 1

Rob W
Rob W

Reputation: 349222

Change

 it("should be greater than 0", function(done) {
   wrapFuncRunInBackground(done);       
   expect(value).toBeGreaterThan(0);
 });

to

 it("should be greater than 0", function(done) {
   wrapFuncRunInBackground(function() {       
     expect(value).toBeGreaterThan(0);
     done();
   });
 });

Callbacks don't pause the execution, so in your original snippet there is nothing that prevents the expect(...) call from being run before the asynchronous callback of wrapFuncRunInBackground is called.

done is not magic, it's just a normal function that marks the test as completed upon invocation...

Upvotes: 1

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