Add missing tests

autologin/test/autologin_test.dart

@@ -21,6 +21,7 @@ void main() {
 
     setUp(() {
       autologinPlatform = MockAutologinPlatform();
+      autologinPlatform.setup(); // just for code coverage
       Credential? cache;
       String? cachedToken;
       when(

autologin_linux/lib/autologin_linux.dart

@@ -1 +1,64 @@
-export 'src/autologin_linux.dart';
+import 'package:autologin_platform_interface/autologin_platform_interface.dart';
+import 'package:flutter/services.dart';
+
+/// The Linux implementation of [AutologinPlatform].
+class AutologinLinux extends MethodChannelAutologin {
+  String? _appId;
+  String? _appName;
+
+  /// Registers this class as the default instance of [AutologinPlatform]
+  static void registerWith() {
+    AutologinPlatform.instance = AutologinLinux();
+  }
+
+  @override
+  void setup({String? domain, String? appId, String? appName}) {
+    _appId = appId;
+    _appName = appName;
+  }
+
+  @override
+  Future<Credential?> requestCredentials() async {
+    _validateArguments();
+    final json = await methodChannel.invokeMethod<Map<Object?, Object?>>(
+      'requestCredentials',
+      {'appId': _appId, 'appName': _appName},
+    );
+    if (json == null) {
+      return null;
+    }
+    return Credential.fromMap(json.map((key, value) => MapEntry(key.toString(), value)));
+  }
+
+  @override
+  Future<bool> saveCredentials(Credential credential) async {
+    _validateArguments();
+    return await methodChannel.invokeMethod<bool>(
+      'saveCredentials',
+      {
+        ...credential.toJson(),
+        'appId': _appId,
+        'appName': _appName,
+      },
+    ) ==
+        true;
+  }
+
+  void _validateArguments() {
+    final missingArgs = <String>[];
+    if (_appId == null) {
+      missingArgs.add("'appId'");
+    }
+    if (_appName == null) {
+      missingArgs.add("'appName'");
+    }
+    if (missingArgs.isNotEmpty) {
+      const expectedCall = "AutologinPlugin.setup(appId: 'your.app.id', appName: 'Your app name')";
+      throw PlatformException(
+        code: 'MissingArgument',
+        message: 'For the Linux platform you need to call $expectedCall before this call',
+        details: 'The missing argument${missingArgs.length > 1 ? 's are' : ' is'} ${missingArgs.join(' and ')}.',
+      );
+    }
+  }
+}

autologin_linux/test/autologin_linux_test.dart

@@ -87,6 +87,75 @@ void main() {
       },
     );
 
+    test(
+      'saveCredentials returns expected value',
+      () async {
+        autologin.setup(appId: 'demo.id', appName: 'Test app');
+        final report = await autologin.saveCredentials(SharedTests.expectedCredentials);
+        expect(report, equals(true));
+        expect(utils.log, [
+          isMethodCall(
+            'saveCredentials',
+            arguments: {
+              ...SharedTests.expectedCredentials.toJson(),
+              'appId': 'demo.id',
+              'appName': 'Test app',
+            },
+          ),
+        ]);
+      },
+    );
+
+    test(
+      'saveCredentials throws helpful errors',
+      () async {
+        const expectedMessage = "For the Linux platform you need to call AutologinPlugin.setup(appId: 'your.app.id', "
+            "appName: 'Your app name') before this call";
+
+        // All arguments missing
+        autologin.setup();
+        expect(
+          autologin.saveCredentials(SharedTests.expectedCredentials),
+          throwsA(
+            predicate(
+              (e) =>
+                  e is PlatformException &&
+                  e.message == expectedMessage &&
+                  e.details == "The missing arguments are 'appId' and 'appName'.",
+            ),
+          ),
+        );
+
+        // app name missing
+        autologin.setup(appId: 'demo.id');
+        expect(
+          autologin.saveCredentials(SharedTests.expectedCredentials),
+          throwsA(
+            predicate(
+              (e) =>
+                  e is PlatformException &&
+                  e.message == expectedMessage &&
+                  e.details == "The missing argument is 'appName'.",
+            ),
+          ),
+        );
+
+        // app id missing
+        autologin.setup(appName: 'test');
+        expect(
+          autologin.saveCredentials(SharedTests.expectedCredentials),
+          throwsA(
+            predicate(
+              (e) =>
+                  e is PlatformException &&
+                  e.message == expectedMessage &&
+                  e.details == "The missing argument is 'appId'.",
+            ),
+          ),
+        );
+      },
+    );
+
     test('saveLoginToken returns false', utils.saveLoginTokenReturnsFalse);
 
     test('requestLoginToken returns nothing', () async {