routing: local balance check

routing/pathfind_test.go

@@ -2271,6 +2271,37 @@ func TestRouteToSelf(t *testing.T) {
 	ctx.assertPath(path, []uint64{1, 3, 2})
 }
 
+// TestInsufficientBalance tests that a dedicated error is returned for
+// insufficient local balance.
+func TestInsufficientBalance(t *testing.T) {
+	t.Parallel()
+
+	testChannels := []*testChannel{
+		symmetricTestChannel("source", "target", 100000, &testChannelPolicy{
+			Expiry:      144,
+			FeeBaseMsat: 500,
+		}, 1),
+	}
+
+	ctx := newPathFindingTestContext(t, testChannels, "source")
+	defer ctx.cleanup()
+
+	paymentAmt := lnwire.NewMSatFromSatoshis(100)
+	target := ctx.keyFromAlias("target")
+
+	ctx.graphParams.bandwidthHints = map[uint64]lnwire.MilliSatoshi{
+		1: lnwire.NewMSatFromSatoshis(50),
+	}
+
+	// Find the best path to self. We expect this to be source->a->source,
+	// because a charges the lowest forwarding fee.
+	_, err := ctx.findPath(target, paymentAmt)
+	if err != errInsufficientBalance {
+		t.Fatalf("expected insufficient balance error, but got: %v",
+			err)
+	}
+}
+
 type pathFindingTestContext struct {
 	t                 *testing.T
 	graphParams       graphParams