test(remote): add tests for prune() method

test/remote_prune_test.dart

@@ -0,0 +1,69 @@
+import 'dart:io';
+import 'package:libgit2dart/src/git_types.dart';
+import 'package:test/test.dart';
+import 'package:libgit2dart/libgit2dart.dart';
+import 'helpers/util.dart';
+
+void main() {
+  late Repository originRepo;
+  late Repository clonedRepo;
+  late Directory tmpDir;
+  late Remote remote;
+  final cloneDir = Directory('${Directory.systemTemp.path}/cloned');
+
+  setUp(() async {
+    tmpDir = await setupRepo(Directory('test/assets/testrepo/'));
+    if (await cloneDir.exists()) {
+      cloneDir.delete(recursive: true);
+    }
+    originRepo = Repository.open(tmpDir.path);
+    clonedRepo = Repository.clone(
+      url: tmpDir.path,
+      localPath: cloneDir.path,
+    );
+    originRepo.branches['feature'].delete();
+    remote = clonedRepo.remotes['origin'];
+  });
+
+  tearDown(() async {
+    remote.free();
+    originRepo.free();
+    clonedRepo.free();
+    await tmpDir.delete(recursive: true);
+    if (await cloneDir.exists()) {
+      cloneDir.delete(recursive: true);
+    }
+  });
+  group('Remote', () {
+    test('fetch() does not prune branch by default', () {
+      remote.fetch();
+      expect(clonedRepo.branches.list(), contains('origin/feature'));
+    });
+
+    test('fetch() successfully prunes branch with provided flag', () {
+      remote.fetch(prune: GitFetchPrune.prune);
+      expect(clonedRepo.branches.list(), isNot(contains('origin/feature')));
+    });
+
+    test('fetch() does not prune branch with provided flag', () {
+      remote.fetch(prune: GitFetchPrune.noPrune);
+      expect(clonedRepo.branches.list(), contains('origin/feature'));
+    });
+
+    test('prune() successfully prunes branches', () {
+      var pruned = <String>[];
+      void updateTips(String refname, Oid oldOid, Oid newOid) {
+        pruned.add(refname);
+      }
+
+      final callbacks = Callbacks(updateTips: updateTips);
+
+      remote.fetch(prune: GitFetchPrune.noPrune);
+      expect(clonedRepo.branches.list(), contains('origin/feature'));
+
+      remote.prune(callbacks);
+      expect(pruned, contains('refs/remotes/origin/feature'));
+      expect(clonedRepo.branches.list(), isNot(contains('origin/feature')));
+    });
+  });
+}