[#493] node/config: Cover ENV variables with unit test

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

cmd/neofs-node/config/calls_test.go

@@ -1,9 +1,11 @@
 package config_test
 
 import (
+	"os"
 	"testing"
 
 	"github.com/nspcc-dev/neofs-node/cmd/neofs-node/config"
+	"github.com/nspcc-dev/neofs-node/cmd/neofs-node/config/internal"
 	configtest "github.com/nspcc-dev/neofs-node/cmd/neofs-node/config/test"
 	"github.com/stretchr/testify/require"
 )
@@ -25,3 +27,18 @@ func TestConfigCommon(t *testing.T) {
 		require.Nil(t, val)
 	})
 }
+
+func TestConfigEnv(t *testing.T) {
+	const (
+		name    = "name"
+		section = "section"
+		value   = "some value"
+	)
+
+	err := os.Setenv(internal.Env(section, name), value)
+	require.NoError(t, err)
+
+	c := configtest.EmptyConfig()
+
+	require.Equal(t, value, c.Sub(section).Value(name))
+}