Guard linux is available around actually installed linux commands.

test/models/external_player_models_test.dart

@@ -0,0 +1,22 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/models/external_player_models.dart';
+
+void main() {
+  test('Linux exposes only known players whose commands are available', () {
+    final players = KnownPlayers.getForCurrentPlatform();
+
+    expect(players.map((player) => player.id), [
+      'system_default',
+      if (_commandIsAvailable('vlc')) 'vlc',
+      if (_commandIsAvailable('mpv')) 'mpv',
+      if (_commandIsAvailable('celluloid')) 'celluloid',
+    ]);
+  }, skip: !Platform.isLinux);
+}
+
+bool _commandIsAvailable(String command) {
+  final result = Process.runSync('sh', ['-c', r'command -v "$1" >/dev/null 2>&1', 'plezy-test-command-probe', command]);
+  return result.exitCode == 0;
+}