1 files changed, 61 insertions, 0 deletions
diff --git a/src/internal/dag/parse_test.go b/src/internal/dag/parse_test.go
new file mode 100644
index 0000000000..b2520c3659
--- /dev/null
+++ b/src/internal/dag/parse_test.go
@@ -0,0 +1,61 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package dag
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+const diamond = `
+NONE < a < b, c < d;
+`
+
+func mustParse(t *testing.T, dag string) *Graph {
+	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)
+			want := wantEdgeMap[n1+"->"+n2]
+			if got && want {
+				t.Logf("%s->%s", n1, n2)
+			} else if got && !want {
+				t.Errorf("%s->%s present but not expected", n1, n2)
+			} else if want && !got {
+				t.Errorf("%s->%s missing but expected", n1, n2)
+			}
+		}
+	}
+}
+
+func TestParse(t *testing.T) {
+	// Basic smoke test for graph parsing.
+	g := mustParse(t, diamond)
+
+	wantNodes := strings.Fields("a b c d")
+	if !reflect.DeepEqual(wantNodes, g.Nodes) {
+		t.Fatalf("want nodes %v, got %v", wantNodes, g.Nodes)
+	}
+
+	// Parse returns the transitive closure, so it adds d->a.
+	wantEdges(t, g, "b->a c->a d->a d->b d->c")
+}