t.Helper()
	g, err := Parse(dag)
	if err != nil {
		t.Fatal(err)
	}
	return g
}

func wantEdges(t *testing.T, g *Graph, edges string) {
	t.Helper()

	wantEdges := strings.Fields(edges)
	wantEdgeMap := make(map[string]bool)
	for _, e := range wantEdges {
		wantEdgeMap[e] = true
	}

	for _, n1 := range g.Nodes {
		for _, n2 := range g.Nodes {
			got := g.HasEdge(n1, n2)

	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) {
		const chain = `NONE < a < b < c < d; a, d < e;`
		g := mustParse(t, chain)
		g.TransitiveReduction()
		wantEdges(t, g, "e->d d->c c->b b->a")
	})