[#493] node/config: Export useful functions into a separate test package

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

cmd/neofs-node/config/test/config.go

@@ -0,0 +1,34 @@
+package configtest
+
+import "github.com/nspcc-dev/neofs-node/cmd/neofs-node/config"
+
+func fromFile(path string) *config.Config {
+	var p config.Prm
+
+	return config.New(p,
+		config.WithConfigFile(path),
+	)
+}
+
+func forEachFile(paths []string, f func(*config.Config)) {
+	for i := range paths {
+		f(fromFile(paths[i]))
+	}
+}
+
+// ForEachFileType passes configs read from next files:
+//  - `<pref>.yaml`;
+//  - `<pref>.json`.
+func ForEachFileType(pref string, f func(*config.Config)) {
+	forEachFile([]string{
+		pref + ".yaml",
+		pref + ".json",
+	}, f)
+}
+
+// EmptyConfig returns config without any values and sections.
+func EmptyConfig() *config.Config {
+	var p config.Prm
+
+	return config.New(p)
+}