unit test for a function that returns nothing

Question

I want to write a unit test for the loadingTime function. This function converts timeTable (type map) into a result array which consists of 0 and 1. Index 3-5 (03:00 - 05:00), 12-14 (12:00 - 14:00) are 1, the rest is 0. Then the result array is assigned to the rowTable. How to write a unit test for this?

timeTable: Map<number, Array<from: string to: string>>

0:[{from: "03:00", to: 05:00"}, {from: "12:00", to:"14:00"}]
1:[{from: "00:00", to: "23:00"}]
2:[{from: "00:00", to: "23:00"}]
3:[{from: "00:00", to: "23:00"}]
4:[{from: "00:00", to: "23:00"}]
5:[{from: "00:00", to: "23:00"}]
6:[{from: "00:00", to: "23:00"}]

rowTable:

 rowTable: Row[] = [
    { name: this.allDays.monday, items: new Array(24).fill(1), active: true },
    { name: this.allDays.tuesday, items: new Array(24).fill(1), active: true },
    { name: this.allDays.wednesday, items: new Array(24).fill(1), active: true },
    { name: this.allDays.thursday, items: new Array(24).fill(1), active: true },
    { name: this.allDays.friday, items: new Array(24).fill(1), active: true },
    { name: this.allDays.saturday, items: new Array(24).fill(1), active: true },
    { name: this.allDays.sunday, items: new Array(24).fill(1), active: true }
  ];

loadingTime

loadingTime(): void {
   if (this.timeTable) {
     let result = [...this.timeTable].reduce((r, [key, value], i) => {
       r[i] = Array(24).fill(0);
       value.forEach(o => {
         let start = getHours(o.from);
         const end = getHours(o.to);
         while (start <= end) {
           r[i][start] = 1;
           start++;
         }
       })
       return r;
     }, []);
 
     this.rowTable.forEach((el, i) => {
       el.items = result[i];
       el.active = false;
     })
   }
 }

my attempts, but I don't know if I'm going in the right direction. Please help

it("should loading Time"), () => {

  const timetableMock = new Map<number, Array<from: string to: string>>()
      timetableMock.set(0, [{ from: '00:00', to: '23:00' }]);

  component.loadingTime = () => {};

  const onSaveSpy = spyOn(component, "loadingTime")

  component.loadingTime();

  expect(onSaveSpy).toEqual([........I don't know what to enter here]);

}

Answer 1

will somethign like this work?

it('loadingTime should not update rowTable if timeTable is undefined', () => {
  const rowTableForEachSpy = jest.spyOn(component.rowTable, 'forEach');
  component.timeTable = void 0;
  component.loadingTime();
  expect(rowTableForEachSpy).not.toHaveBeenCalled();
  // in addition you can most probably assert `component.rowTable` value here
})

it('loadingTime should update rowTable if timeTable is defined', () => {
  const rowTableForEachSpy = jest.spyOn(component.rowTable, 'forEach');
  component.timeTable = new Map(...);
  component.loadingTime();
  expect(rowTableForEachSpy).toHaveBeenCalled();
  // in addition you can most probably assert `component.rowTable` value here
})