feat: add getLatestVersion

.gitignore

@@ -4,4 +4,6 @@
 .dart_tool/
 .packages
 build/
-pubspec.lock
+pubspec.lock
+.test_coverage.dart
+coverage/

lib/src/pub_updater.dart

@@ -9,7 +9,7 @@ import 'package:pub_updater/pub_updater.dart';
 class PackageInfoRequestFailure implements Exception {}
 
 /// Exception thrown when the provided package information is not found.
-class PackageInfoNotFoundFailue implements Exception {}
+class PackageInfoNotFoundFailure implements Exception {}
 
 /// {@template pub_update}
 /// A Dart package which enables checking whether a package is up to date.
@@ -30,33 +30,42 @@ class PubUpdater {
     required String packageName,
     required String currentVersion,
   }) async {
-    final uri = Uri.parse('$_baseUrl$packageName.json');
-    final response = await _get(uri);
-
-    if (response.statusCode != HttpStatus.ok) throw PackageInfoRequestFailure();
+    final latestVersion = await getLatestVersion(packageName);
 
-    final packageInfo = _getPackageInfo(response.body);
+    return currentVersion == latestVersion;
+  }
 
-    final versionList = packageInfo.versions..sort();
+  /// Returns the latest published version of [packageName].
+  Future<String> getLatestVersion(String packageName) async {
+    final packageInfo = await _getPackageInfo(packageName);
+    final versions = packageInfo.versions..sort();
 
-    return versionList.last == currentVersion;
+    return versions.last;
   }
 
   /// Updates the package associated with [packageName]
   Future<ProcessResult> update({
     required String packageName,
     ProcessManager processManager = const LocalProcessManager(),
   }) {
-    return processManager
-        .run(['dart', 'pub', 'global', 'activate', packageName]);
+    return processManager.run(
+      ['dart', 'pub', 'global', 'activate', packageName],
+    );
+  }
+
+  Future<PackageInfo> _getPackageInfo(String packageName) async {
+    final uri = Uri.parse('$_baseUrl$packageName.json');
+    final response = await _get(uri);
+
+    if (response.statusCode != HttpStatus.ok) throw PackageInfoRequestFailure();
+
+    return _decodePackageInfo(response.body);
   }
 
-  PackageInfo _getPackageInfo(String body) {
+  PackageInfo _decodePackageInfo(String body) {
     final packageJson = jsonDecode(body) as Map<String, dynamic>;
 
-    if (packageJson.isEmpty) {
-      throw PackageInfoNotFoundFailue();
-    }
+    if (packageJson.isEmpty) throw PackageInfoNotFoundFailure();
 
     return PackageInfo.fromJson(packageJson);
   }

test/pub_update_test.dart

@@ -176,7 +176,67 @@ void main() {
             packageName: 'very_good_cli',
             currentVersion: '3.0.0',
           ),
-          throwsA(isA<PackageInfoNotFoundFailue>()),
+          throwsA(isA<PackageInfoNotFoundFailure>()),
+        );
+      });
+    });
+
+    group('getLatestVersion', () {
+      test('makes correct http request', () async {
+        when(() => response.body).thenReturn(emptyResponseBody);
+
+        try {
+          await pubUpdater.getLatestVersion('very_good_cli');
+        } catch (_) {
+          verify(
+            () => client.get(
+              Uri.https(
+                'pub.dev',
+                '/packages/very_good_cli.json',
+              ),
+            ),
+          ).called(1);
+        }
+      });
+
+      test('returns correct version (dev)', () async {
+        when(() => response.body).thenReturn(devResponseBody);
+        expect(
+          await pubUpdater.getLatestVersion('very_good_cli'),
+          equals('3.0.0-dev.2'),
+        );
+      });
+
+      test('returns correct version (nullsafety)', () async {
+        when(() => response.body).thenReturn(nullSafetyReponseBody);
+        expect(
+          await pubUpdater.getLatestVersion('very_good_cli'),
+          equals('3.0.0-nullsafety.1'),
+        );
+      });
+
+      test('returns correct version (all)', () async {
+        when(() => response.body).thenReturn(responseBody);
+        expect(
+          await pubUpdater.getLatestVersion('very_good_cli'),
+          equals('3.0.0-nullsafety.1'),
+        );
+      });
+
+      test('throws PackageInfoRequestFailure on non-200 response', () async {
+        when(() => response.statusCode).thenReturn(HttpStatus.notFound);
+        await expectLater(
+          pubUpdater.getLatestVersion('very_good_cli'),
+          throwsA(isA<PackageInfoRequestFailure>()),
+        );
+      });
+
+      test('throws PackageInfoNotFoundFailure when response body is empty',
+          () async {
+        when(() => response.body).thenReturn(emptyResponseBody);
+        await expectLater(
+          pubUpdater.getLatestVersion('very_good_cli'),
+          throwsA(isA<PackageInfoNotFoundFailure>()),
         );
       });
     });