func (g *dotDirectedGraph) NewEdge(from, to graph.Node) graph.Edge {
	return &dotEdge{Edge: g.DirectedGraph.NewEdge(from, to)}
}
NewEdge returns a new Edge from the source to the destination node.
package dot
import (
	"fmt"
	"testing"
	"gonum.org/v1/gonum/graph"
	"gonum.org/v1/gonum/graph/encoding"
	"gonum.org/v1/gonum/graph/simple"
)
func TestRoundTrip(t *testing.T) {
	golden := []struct {
		want     string
		directed bool
	}{
		{
			want:     directed,
			directed: true,
		},
		{
			want:     undirected,
			directed: false,
		},
		{
			want:     directedID,
			directed: true,
		},
		{
			want:     undirectedID,
			directed: false,
		},
	}
	for i, g := range golden {
		var dst encoding.Builder
		if g.directed {
			dst = newDotDirectedGraph()
		} else {
			dst = newDotUndirectedGraph()
		}
		data := []byte(g.want)
		if err := Unmarshal(data, dst); err != nil {
			t.Errorf("i=%d: unable to unmarshal DOT graph; %v", i, err)
			continue
		}
		buf, err := Marshal(dst, "", "", "\t", false)
		if err != nil {
			t.Errorf("i=%d: unable to marshal graph; %v", i, dst)
			continue
		}
		got := string(buf)
		if got != g.want {
			t.Errorf("i=%d: graph content mismatch; want:\n%s\n\ngot:\n%s", i, g.want, got)
			continue
		}
	}
}
const directed = `digraph {
	graph [
		outputorder=edgesfirst
	];
	node [
		shape=circle
		style=filled
	];
	edge [
		penwidth=5
		color=gray
	];
	A [label="foo 2"];
	B [label="bar 2"];
	A -> B [label="baz 2"];
}`
const undirected = `graph {
	graph [
		outputorder=edgesfirst
	];
	node [
		shape=circle
		style=filled
	];
	edge [
		penwidth=5
		color=gray
	];
	A [label="foo 2"];
	B [label="bar 2"];
	A -- B [label="baz 2"];
}`
const directedID = `digraph G {
	A;
	B;
	A -> B;
}`
const undirectedID = `graph H {
	A;
	B;
	A -- B;
}`
type dotDirectedGraph struct {
	*simple.DirectedGraph
	id                string
	graph, node, edge attributes
}
func newDotDirectedGraph() *dotDirectedGraph {
	return &dotDirectedGraph{DirectedGraph: simple.NewDirectedGraph()}
}
func (g *dotDirectedGraph) NewNode() graph.Node {
	return &dotNode{Node: g.DirectedGraph.NewNode()}
}