add dump refereence env provider

provider/env/provider_test.go

@@ -1,10 +1,17 @@
 package env_test
 
 import (
+	"bytes"
+	"context"
 	"testing"
 
+	"gitoa.ru/go-4devs/config"
+	"gitoa.ru/go-4devs/config/definition/group"
+	"gitoa.ru/go-4devs/config/definition/option"
+	"gitoa.ru/go-4devs/config/definition/proto"
 	"gitoa.ru/go-4devs/config/provider/env"
 	"gitoa.ru/go-4devs/config/test"
+	"gitoa.ru/go-4devs/config/test/require"
 )
 
 func TestProvider(t *testing.T) {
@@ -19,3 +26,35 @@ func TestProvider(t *testing.T) {
 	}
 	test.Run(t, provider, read)
 }
+
+func TestProvider_DumpReference(t *testing.T) {
+	t.Parallel()
+
+	const expect = `# configure log.
+# level.
+FDEVS_CONFIG_LOG_LEVEL=info
+# configure log service.
+# level.
+#FDEVS_CONFIG_LOG_{SERVICE}_LEVEL=
+`
+
+	ctx := context.Background()
+	prov := env.New("fdevs", "config")
+	buf := bytes.NewBuffer(nil)
+
+	require.NoError(t, prov.DumpReference(ctx, buf, testOptions(t)))
+	require.Equal(t, buf.String(), expect)
+}
+
+func testOptions(t *testing.T) config.Options {
+	t.Helper()
+
+	return group.New("test", "test",
+		group.New("log", "configure log",
+			option.String("level", "level", option.Default("info")),
+			proto.New("service", "configure log service",
+				option.String("level", "level"),
+			),
+		),
+	)
+}