From 31ca5c14d33addfd6d8bb86e2c29861bb70d3089 Mon Sep 17 00:00:00 2001
From: Pavel Karpy <carpawell@nspcc.ru>
Date: Tue, 8 Jun 2021 15:15:45 +0300
Subject: [PATCH] [#302] pkg/container/id: Document default values set in `New`

Document field values of instance constructed via `New`.
Assert the values in corresponding unit test.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>
---
 pkg/container/id/id.go      |  5 ++++-
 pkg/container/id/id_test.go | 24 ++++++++++++++++++++----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/pkg/container/id/id.go b/pkg/container/id/id.go
index b09c7b33..351c9b31 100644
--- a/pkg/container/id/id.go
+++ b/pkg/container/id/id.go
@@ -20,6 +20,9 @@ func NewFromV2(idV2 *refs.ContainerID) *ID {
 }
 
 // New creates and initializes blank ID.
+//
+// Defaults:
+//  - value: nil.
 func New() *ID {
 	return NewFromV2(new(refs.ContainerID))
 }
@@ -31,7 +34,7 @@ func (id *ID) SetSHA256(v [sha256.Size]byte) {
 
 // ToV2 returns the v2 container ID message.
 //
-// Nil Result converts to nil.
+// Nil ID converts to nil.
 func (id *ID) ToV2() *refs.ContainerID {
 	return (*refs.ContainerID)(id)
 }
diff --git a/pkg/container/id/id_test.go b/pkg/container/id/id_test.go
index e0a266ee..b633cb4b 100644
--- a/pkg/container/id/id_test.go
+++ b/pkg/container/id/id_test.go
@@ -33,6 +33,14 @@ func TestID_ToV2(t *testing.T) {
 
 		require.Nil(t, x.ToV2())
 	})
+
+	t.Run("default values", func(t *testing.T) {
+		cid := cid.New()
+
+		// convert to v2 message
+		cidV2 := cid.ToV2()
+		require.Nil(t, cidV2.GetValue())
+	})
 }
 
 func TestID_Equal(t *testing.T) {
@@ -49,11 +57,19 @@ func TestID_Equal(t *testing.T) {
 }
 
 func TestID_String(t *testing.T) {
-	id := cidtest.Generate()
-	id2 := cid.New()
+	t.Run("Parse/String", func(t *testing.T) {
+		id := cidtest.Generate()
+		id2 := cid.New()
 
-	require.NoError(t, id2.Parse(id.String()))
-	require.Equal(t, id, id2)
+		require.NoError(t, id2.Parse(id.String()))
+		require.Equal(t, id, id2)
+	})
+
+	t.Run("nil", func(t *testing.T) {
+		id := cid.New()
+
+		require.Empty(t, id.String())
+	})
 }
 
 func TestContainerIDEncoding(t *testing.T) {