Function TestCellIDDistanceToBegin

s2/cellid_test.go:602–643

(t *testing.T)

}

func TestCellIDDistanceToBegin(t *testing.T) {
	tests := []struct {
		id   CellID
		want int64
	}{
		{
			// at level 0 (i.e. full faces), there are only 6 cells from
			// the last face to the beginning of the Hilbert curve.
			id:   CellIDFromFace(5).ChildEndAtLevel(0),
			want: 6,
		},
		{
			// from the last cell on the last face at the smallest cell size,
			// there are the maximum number of possible cells.
			id:   CellIDFromFace(5).ChildEndAtLevel(MaxLevel),
			want: 6 * (1 << uint(2*MaxLevel)),
		},
		{
			// from the first cell on the first face.
			id:   CellIDFromFace(0).ChildBeginAtLevel(0),
			want: 0,
		},
		{
			// from the first cell at the smallest level on the first face.
			id:   CellIDFromFace(0).ChildBeginAtLevel(MaxLevel),
			want: 0,
		},
	}

	for _, test := range tests {
		if got := test.id.distanceFromBegin(); got != test.want {
			t.Errorf("%v.distanceToBegin() = %v, want %v", test.id, got, test.want)
		}
	}

	// Test that advancing from the beginning by the distance from a cell gets
	// us back to that cell.
	id := CellIDFromFacePosLevel(3, 0x12345678, MaxLevel-4)
	if got := CellIDFromFace(0).ChildBeginAtLevel(id.Level()).Advance(id.distanceFromBegin()); got != id {
		t.Errorf("advancing from the beginning by the distance of a cell should return us to that cell. got %v, want %v", got, id)
	}
}

func TestCellIDWrapping(t *testing.T) {
	id := CellIDFromFacePosLevel(3, 0x12345678, MaxLevel-4)