add tests

internal/restrictednet/settings.go

@@ -0,0 +1,36 @@
+package restrictednet
+
+import (
+	"errors"
+	"net/http"
+
+	"github.com/qdm12/dns/v2/pkg/provider"
+)
+
+type Settings struct {
+	DefaultInterface  string
+	IPv6Supported     *bool
+	Firewall          Firewall
+	UpstreamResolvers []provider.Provider
+	BaseTransport     *http.Transport
+}
+
+func (s *Settings) setDefaults() {
+	if s.BaseTransport == nil {
+		s.BaseTransport = http.DefaultTransport.(*http.Transport) //nolint:forcetypeassert
+	}
+}
+
+func (s *Settings) validate() error {
+	switch {
+	case s.DefaultInterface == "":
+		return errors.New("default interface is not set")
+	case s.IPv6Supported == nil:
+		return errors.New("IPv6 support field is not set")
+	case s.Firewall == nil:
+		return errors.New("firewall is not set")
+	case len(s.UpstreamResolvers) == 0:
+		return errors.New("no upstream resolvers provided")
+	}
+	return nil
+}