path/resolver_test: Test recursive Link resolution

Setup a three-level graph:

  a -(child)-> b -(grandchild)-> c

and then try and resolve:

  /ipfs/<hash-of-a>/child/grandchild

Before 10669e8b (path/resolver: Fix recursive path resolution,
2015-05-08) this failed with:

  resolver_test.go:71: no link named "grandchild" under QmSomeRandomHash

The boilerplate for this test is from pin/pin_test.go, and I make no
claims that it's the best way to setup the test graph ;).

path/resolver_test.go

@@ -0,0 +1,83 @@
+package path_test
+
+import (
+	"fmt"
+	"testing"
+
+	datastore "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	sync "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/sync"
+	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+
+	blockstore "github.com/ipfs/go-ipfs/blocks/blockstore"
+	blockservice "github.com/ipfs/go-ipfs/blockservice"
+	offline "github.com/ipfs/go-ipfs/exchange/offline"
+	merkledag "github.com/ipfs/go-ipfs/merkledag"
+	path "github.com/ipfs/go-ipfs/path"
+	util "github.com/ipfs/go-ipfs/util"
+)
+
+func randNode() (*merkledag.Node, util.Key) {
+	node := new(merkledag.Node)
+	node.Data = make([]byte, 32)
+	util.NewTimeSeededRand().Read(node.Data)
+	k, _ := node.Key()
+	return node, k
+}
+
+func TestRecurivePathResolution(t *testing.T) {
+	ctx := context.Background()
+	dstore := sync.MutexWrap(datastore.NewMapDatastore())
+	bstore := blockstore.NewBlockstore(dstore)
+	bserv, err := blockservice.New(bstore, offline.Exchange(bstore))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	dagService := merkledag.NewDAGService(bserv)
+
+	a, _ := randNode()
+	b, _ := randNode()
+	c, cKey := randNode()
+
+	err = b.AddNodeLink("grandchild", c)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = a.AddNodeLink("child", b)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = dagService.AddRecursive(a)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	aKey, err := a.Key()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	segments := []string{"", "ipfs", aKey.String(), "child", "grandchild"}
+	p, err := path.FromSegments(segments...)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	resolver := &path.Resolver{DAG: dagService}
+	node, err := resolver.ResolvePath(ctx, p)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	key, err := node.Key()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if key.String() != cKey.String() {
+		t.Fatal(fmt.Errorf(
+			"recursive path resolution failed for %s: %s != %s",
+			p.String(), key.String(), cKey.String()))
+	}
+}