Move internal packages to an internal folder

For reference: https://go.dev/doc/go1.4#internalpackages

internal/reader/opml/serializer_test.go

@@ -0,0 +1,63 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package opml // import "miniflux.app/v2/internal/reader/opml"
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestSerialize(t *testing.T) {
+	var subscriptions SubcriptionList
+	subscriptions = append(subscriptions, &Subcription{Title: "Feed 1", FeedURL: "http://example.org/feed/1", SiteURL: "http://example.org/1", CategoryName: "Category 1"})
+	subscriptions = append(subscriptions, &Subcription{Title: "Feed 2", FeedURL: "http://example.org/feed/2", SiteURL: "http://example.org/2", CategoryName: "Category 1"})
+	subscriptions = append(subscriptions, &Subcription{Title: "Feed 3", FeedURL: "http://example.org/feed/3", SiteURL: "http://example.org/3", CategoryName: "Category 2"})
+
+	output := Serialize(subscriptions)
+	feeds, err := Parse(bytes.NewBufferString(output))
+	if err != nil {
+		t.Error(err)
+	}
+
+	if len(feeds) != 3 {
+		t.Errorf("Wrong number of subscriptions: %d instead of %d", len(feeds), 3)
+	}
+
+	found := false
+	for _, feed := range feeds {
+		if feed.Title == "Feed 1" && feed.CategoryName == "Category 1" &&
+			feed.FeedURL == "http://example.org/feed/1" && feed.SiteURL == "http://example.org/1" {
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		t.Error("Serialized feed is incorrect")
+	}
+}
+
+func TestNormalizedCategoriesOrder(t *testing.T) {
+	var orderTests = []struct {
+		naturalOrderName string
+		correctOrderName string
+	}{
+		{"Category 2", "Category 1"},
+		{"Category 3", "Category 2"},
+		{"Category 1", "Category 3"},
+	}
+
+	var subscriptions SubcriptionList
+	subscriptions = append(subscriptions, &Subcription{Title: "Feed 1", FeedURL: "http://example.org/feed/1", SiteURL: "http://example.org/1", CategoryName: orderTests[0].naturalOrderName})
+	subscriptions = append(subscriptions, &Subcription{Title: "Feed 2", FeedURL: "http://example.org/feed/2", SiteURL: "http://example.org/2", CategoryName: orderTests[1].naturalOrderName})
+	subscriptions = append(subscriptions, &Subcription{Title: "Feed 3", FeedURL: "http://example.org/feed/3", SiteURL: "http://example.org/3", CategoryName: orderTests[2].naturalOrderName})
+
+	feeds := convertSubscriptionsToOPML(subscriptions)
+
+	for i, o := range orderTests {
+		if feeds.Outlines[i].Text != o.correctOrderName {
+			t.Fatalf("need %v, got %v", o.correctOrderName, feeds.Outlines[i].Text)
+		}
+	}
+}