Trying to get my unit test coverage for this bit of code:

  processUpdates(input) {
    let request = [];
    this.gridApi.forEachNode(function (node) { // <--- How to mock/spy inside forEachNode
      if (input.has(data.id)) {
        request.push(this.createRequestRowUpdate(node, input));
      }
      this.someCoolService.saveMychanges(request).pipe(map(res => res as any)).subscribe(res => {
        //success 
      }, (error: HttpErrorResponse) => {
        //failure
      });
    });
  }

How can I set my test up so I can make some assertions on inside the forEachNode call on the gridApi?

example

expect(service['saveMychanges']).toHaveBeenCalledOnce();

Reference

https://www.ag-grid.com/javascript-data-grid/grid-api/#reference-rowNodes-forEachNode