javascript - How to spy on static generator functions? -

i have utility function exposes generator:

export class utility {     // provides generator streams 2^n binary combinations n variables     public static *binarycombinationgenerator(numvars: number): iterableiterator<boolean[]> {         (let = 0; < math.pow(2, numvars); i++) {             const c = [];            //fill c             yield c;         }     } } 

now, using generator in code follows:

myfuncion(input){     const n = numberofvariables(input);     const binarycombinations = utility.binarycombinationgenerator(n);     let combination: boolean[] = binarycombinations.next().value;     while (till termination condition met) {       // , check whether termination condition met                combination = binarycombinations.next().value;     } } 

in unit tests (using jasmine) want verify how many times generator function invoked (i.e. how many combinations generated) before termination. below have tried:

it("my spec", () => {     //arrange     const generatorspy = spyon(utility, "binarycombinationgenerator").and.callthrough();     //act     //assert     expect(generatorspy).tohavebeencalledtimes(16); // fails with: expected spy binarycombinationgenerator have been called 16 times. called 1 times. }); 

however, assertion fails binarycombinationgenerator indeed called once. want spy on next method of iterableiterator.

however, not sure how that. please suggest.

you return jasmine spy object utility.binarycombinationgenerator method

let binarycombinationsspy = jasmine.createspyobject('binarycombinations', ['next']); binarycombinationsspy.next.and.returnvalues(value1, value2); spyon(utility, "binarycombinationgenerator").and.returnvalue(binarycombinationsspy);  expect(binarycombinationsspy.next).tohavebeencalledtimes(2);