Stubbing computed property for another computed unit test

[jonnyparris]

Hello - how should I stub the value of a computed property in a unit test?

I've got a computed method on my component:

visibleRows () {
  return this.sortedRows.slice(this.firstVisibleRowIndex, this.lastVisibleRowIndex);
},

that I've tried testing with the following:

wrapper.setData({
  sortedRows: dummyData.data
});
assert.equal(wrapper.vm.visibleRows, dummyData.data.slice(0, 4));

However, sortedRows logs as empty within the visibleRows method when the unit test runs.
Any help much appreciated