//
	// "a" is a leaf.
	wantNodes := strings.Fields("d c b a")
	if !reflect.DeepEqual(wantNodes, got) {
		t.Fatalf("want topo sort %v, got %v", wantNodes, got)
	}
}

func TestTransitiveReduction(t *testing.T) {
	t.Run("diamond", func(t *testing.T) {
		g := mustParse(t, diamond)
		g.TransitiveReduction()
		wantEdges(t, g, "b->a c->a d->b d->c")
	})
	t.Run("chain", func(t *testing.T) {