Question

I’m writing a test where I force an exception, and then call the same function in the catch block.

In my test, I need to spy on localStorage.setItem one time, which is where I simulate the exception. When the caller gets called again, I need to either remove the spy or somehow prevent the catch block from being hit again.

it('handles quota_exceeded exceptions', function() {
   spyOn(localStorage, 'setItem').andCallFake(function() {
      throw new Error("QUOTA_EXCEEDED_ERR", "QUOTA_EXCEEDED_ERR: DOM Exception 22");
   });
   spyOn(Obj, 'add').andCallThrough();
   spyOn(Obj, 'clean');

   expect(function() {
      Obj.add('foo', 'bar');
   }).not.toThrow();
   expect(Garage.add.callCount).toBe(2);
});

The test code above produces an infinite loop, as the localStorage.setItem sets off an exception every time.

Any ideas or alternate testing patterns would be appreciated.

Thanks

Answer 1

You could store the localStorage quota status at a local variable. Something like:

it('handles quota_exceeded exceptions', function() {
   var quota_exceeded = true;

   spyOn(localStorage, 'setItem').andCallFake(function() {
      if (quota_exceeded) {
         throw new Error("QUOTA_EXCEEDED_ERR", "QUOTA_EXCEEDED_ERR: DOM Exception 22");
      }
   });
   spyOn(Obj, 'add').andCallThrough();
   spyOn(Obj, 'clean').andCallFake(function () {
       quota_exceeded = false;
   });

   expect(function() {
      Obj.add('foo', 'bar');
   }).not.toThrow();
   expect(Garage.add.callCount).toBe(2);
});