From 70d0f13c9caa6ce618f7260fde84bbba9d50173c Mon Sep 17 00:00:00 2001
From: Lucas Molas <schomatis@gmail.com>
Date: Wed, 18 Jul 2018 11:07:52 -0300
Subject: [PATCH] unixfs/mod: add test to `Truncate` to the same size

License: MIT
Signed-off-by: Lucas Molas <schomatis@gmail.com>
---
 unixfs/mod/dagmodifier_test.go | 38 ++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/unixfs/mod/dagmodifier_test.go b/unixfs/mod/dagmodifier_test.go
index 92e4ce2d6..0a5c5a74f 100644
--- a/unixfs/mod/dagmodifier_test.go
+++ b/unixfs/mod/dagmodifier_test.go
@@ -406,6 +406,44 @@ func testDagTruncate(t *testing.T, opts testu.NodeOpts) {
 	}
 }
 
+// TestDagTruncateSameSize tests that a DAG truncated
+// to the same size (i.e., doing nothing) doesn't modify
+// the DAG (its hash).
+func TestDagTruncateSameSize(t *testing.T) {
+	runAllSubtests(t, testDagTruncateSameSize)
+}
+func testDagTruncateSameSize(t *testing.T, opts testu.NodeOpts) {
+	dserv := testu.GetDAGServ()
+	_, n := testu.GetRandomNode(t, dserv, 50000, opts)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	dagmod, err := NewDagModifier(ctx, n, dserv, testu.SizeSplitterGen(512))
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Copied from `TestDagTruncate`.
+
+	size, err := dagmod.Size()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = dagmod.Truncate(size)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	modifiedNode, err := dagmod.GetNode()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if modifiedNode.Cid().Equals(n.Cid()) == false {
+		t.Fatal("the node has been modified!")
+	}
+}
+
 func TestSparseWrite(t *testing.T) {
 	runAllSubtests(t, testSparseWrite)
 }