AWS supports the following Ruby runtimes:

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Name | Identifier | SDK for Ruby | Operating system
-- | -- | -- | --
Ruby 2.7 | ruby2.7 | 3.0.1 | Amazon Linux 2
Ruby 2.5 | ruby2.5 | 3.0.1 | Amazon Linux

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Currently, `localstack/lambda` only contains the `ruby2.5` tag. Will the 2.7 runtime be supported in the (near) future?
@classmethod
    def setUpClass(cls):
        cls.lambda_client = aws_stack.connect_to_service('lambda')
        
        if not os.path.exists(TEST_LAMBDA_JAVA):
            mkdir(os.path.dirname(TEST_LAMBDA_JAVA))
            download(TEST_LAMBDA_JAR_URL, TEST_LAMBDA_JAVA)
        
        cls.test_java_jar = load_file(TEST_LAMBDA_JAVA, mode='rb')
        zip_dir = new_tmp_dir()
        zip_lib_dir = os.path.join(zip_dir, 'lib')
        zip_jar_path = os.path.join(zip_lib_dir, 'test.lambda.jar')
        mkdir(zip_lib_dir)
        cp_r(INSTALL_PATH_LOCALSTACK_FAT_JAR, os.path.join(zip_lib_dir, 'executor.lambda.jar'))
        save_file(zip_jar_path, cls.test_java_jar)
        cls.test_java_zip = testutil.create_zip_file(zip_dir, get_content=True)
        testutil.create_lambda_function(
            func_name=TEST_LAMBDA_NAME_JAVA,
            zip_file=cls.test_java_zip,
            runtime=LAMBDA_RUNTIME_JAVA8,
            handler='cloud.localstack.sample.LambdaHandler'
        )
        
        
        testutil.create_lambda_function(
            func_name=TEST_LAMBDA_NAME_JAVA_STREAM,
            zip_file=cls.test_java_jar,
            runtime=LAMBDA_RUNTIME_JAVA8,
            handler='cloud.localstack.sample.LambdaStreamHandler'
        )