[#302] pkg/version: Document default values set in NewVersion

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

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/version.go

@@ -21,6 +21,10 @@ func NewVersionFromV2(v *refs.Version) *Version {
 // NewVersion creates and initializes blank Version.
 //
 // Works similar as NewVersionFromV2(new(Version)).
+//
+// Defaults:
+//  - major: 0;
+//  - minor: 0.
 func NewVersion() *Version {
 	return NewVersionFromV2(new(refs.Version))
 }

pkg/version_test.go

@@ -8,6 +8,21 @@ import (
 )
 
 func TestNewVersion(t *testing.T) {
+	t.Run("default values", func(t *testing.T) {
+		v := NewVersion()
+
+		// check initial values
+		require.Zero(t, v.Major())
+		require.Zero(t, v.Minor())
+
+		// convert to v2 message
+		vV2 := v.ToV2()
+
+		require.Empty(t, vV2.GetMajor())
+		require.Empty(t, vV2.GetMinor())
+	})
+
+	t.Run("setting values", func(t *testing.T) {
 		v := NewVersion()
 
 		var mjr, mnr uint32 = 1, 2
@@ -22,6 +37,7 @@ func TestNewVersion(t *testing.T) {
 
 		require.Equal(t, mjr, ver.GetMajor())
 		require.Equal(t, mnr, ver.GetMinor())
+	})
 }
 
 func TestSDKVersion(t *testing.T) {