Integrate logging system into Flutter app with service registration and testing setup

finlog_app/fluttery/test/logger/logger_test.dart

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+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:logging/logging.dart' as lib;
+import 'package:fluttery/src/logger/logger_impl.dart';
+
+// Mock class for the lib.Logger
+class MockLibLogger extends Mock implements lib.Logger {}
+
+void main() {
+  final mockLibLogger = MockLibLogger();
+
+  group('LoggerImpl', () {
+    late LoggerImpl loggerImpl;
+
+    setUp(() {
+      loggerImpl = LoggerImpl.forTest(mockLibLogger);
+    });
+
+    test('info method logs an info message', () {
+      loggerImpl.info('Info message');
+
+      // Verify that the info method was called on the mock logger with the correct message
+      verify(() => mockLibLogger.info('Info message')).called(1);
+    });
+
+    test('warning method logs a warning message', () {
+      loggerImpl.warning('Warning message');
+
+      // Verify that the warning method was called on the mock logger with the correct message
+      verify(() => mockLibLogger.warning('Warning message')).called(1);
+    });
+
+    test('error method logs an error message with optional parameters', () {
+      final exception = Exception('Test exception');
+      final stackTrace = StackTrace.current;
+
+      loggerImpl.error('Error message', exception, stackTrace);
+
+      // Verify that the severe method was called on the mock logger with the correct parameters
+      verify(
+        () => mockLibLogger.severe('Error message', exception, stackTrace),
+      ).called(1);
+    });
+
+    test('debug method logs a debug message', () {
+      loggerImpl.debug('Debug message');
+
+      // Verify that the fine method was called on the mock logger with the correct message
+      verify(() => mockLibLogger.fine('Debug message')).called(1);
+    });
+
+    test('setLogLevel method sets the logger level', () {
+      // This is to capture the change in the logger level
+      var capturedLevel = lib.Level.INFO;
+
+      // Capture the setter call
+      when(() => mockLibLogger.level = any()).thenAnswer((invocation) {
+        capturedLevel = invocation.positionalArguments.first as lib.Level;
+        return capturedLevel;
+      });
+
+      // Set the log level
+      loggerImpl.setLogLevel(lib.Level.WARNING);
+
+      // Verify that the logger level is set to the expected level
+      expect(capturedLevel, lib.Level.WARNING);
+    });
+  });
+}