feat: Allow PubUpdater to be instantiated with custom dart api base url

lib/src/pub_updater.dart

@@ -11,16 +11,20 @@ class PackageInfoRequestFailure implements Exception {}
 /// Exception thrown when the provided package information is not found.
 class PackageInfoNotFoundFailure implements Exception {}
 
+/// The pub.dev base url for querying package versions
+const _defaultBaseUrl = 'https://pub.dev/api/packages/';
+
 /// {@template pub_update}
 /// A Dart package which enables checking whether a package is up to date.
 /// {@endtemplate}
 class PubUpdater {
   /// {@macro pub_update}
-  PubUpdater([http.Client? client]) : _client = client;
+  PubUpdater([http.Client? client, String baseUrl = _defaultBaseUrl])
+      : _client = client,
+        _baseUrl = baseUrl;
 
-  /// The pub.dev base url for querying package versions
-  static const _baseUrl = 'https://pub.dev/api/packages/';
   final http.Client? _client;
+  final String _baseUrl;
 
   Future<http.Response> _get(Uri uri) => _client?.get(uri) ?? http.get(uri);
 

test/pub_update_test.dart

@@ -21,12 +21,15 @@ const emptyResponseBody = '{}';
 
 const command = ['dart', 'pub', 'global', 'activate', 'very_good_cli'];
 
+const customBaseUrl = 'https://custom-domain.com/api/packages/';
+
 void main() {
   group('PubUpdater', () {
     late Client client;
     late Response response;
     late PubUpdater pubUpdater;
     late ProcessManager processManager;
+
     setUpAll(() {
       registerFallbackValue(Uri());
     });
@@ -49,6 +52,10 @@ void main() {
       expect(PubUpdater(), isNotNull);
     });
 
+    test('can be instantiated with a custom base url', () {
+      expect(PubUpdater(null, customBaseUrl), isNotNull);
+    });
+
     group('isUpToDate', () {
       test('makes correct http request', () async {
         when(() => response.body).thenReturn(emptyResponseBody);
@@ -70,6 +77,24 @@ void main() {
         ).called(1);
       });
 
+      test('makes correct http request with a custom base url', () async {
+        when(() => response.body).thenReturn(emptyResponseBody);
+        pubUpdater = PubUpdater(client, customBaseUrl);
+
+        try {
+          await pubUpdater.isUpToDate(
+            packageName: 'very_good_cli',
+            currentVersion: '0.3.3',
+          );
+        } catch (_) {}
+
+        verify(
+          () => client.get(
+            Uri.parse('${customBaseUrl}very_good_cli'),
+          ),
+        ).called(1);
+      });
+
       test('returns false when currentVersion < latestVersion', () async {
         expect(
           await pubUpdater.isUpToDate(
@@ -132,6 +157,21 @@ void main() {
         ).called(1);
       });
 
+      test('makes correct http request with a custom base url', () async {
+        when(() => response.body).thenReturn(emptyResponseBody);
+        pubUpdater = PubUpdater(client, customBaseUrl);
+
+        try {
+          await pubUpdater.getLatestVersion('very_good_cli');
+        } catch (_) {}
+
+        verify(
+          () => client.get(
+            Uri.parse('${customBaseUrl}very_good_cli'),
+          ),
+        ).called(1);
+      });
+
       test('returns correct version', () async {
         when(() => response.body).thenReturn(validPackageInfoResponseBody);
         expect(