Non-repudiation refers to the ability to prove that a particular action or transaction has occurred and cannot be denied later. In authentication testing, ensuring non-repudiation is a significant challenge because it requires implementing mechanisms that reliably associate actions with specific users or entities, making it difficult for them to deny their involvement. Strong passwords, secure transmission, and user privacy are all important aspects of authentication testing but do not directly address the challenge of non-repudiation.

A data mapping document serves to define the mapping between source and target data fields, crucial for ensuring data consistency during migration.

Test reporting and metrics play a crucial role in ensuring the success of database testing best practices by providing insights into the efficiency of the testing process. Through comprehensive test reporting, stakeholders can track the progress of testing, identify areas that require attention, and assess the overall quality of the database. Metrics, such as defect density and test coverage, offer quantitative measures of testing effectiveness, enabling teams to make data-driven decisions and continuously improve their testing strategies.

A subquery enclosed in parentheses is commonly referred to as a nested subquery. It's a query within another query, often used to perform operations based on the results of the outer query.

Apache Airflow is often used for managing and scheduling ETL (Extract, Transform, Load) jobs. It provides a platform to programmatically author, schedule, and monitor workflows, making it easier to manage complex ETL processes efficiently.

Poor exception handling can lead to the system failing to recover gracefully during stress testing. When the system encounters exceptional conditions under stress, such as reaching its limits, proper exception handling ensures that it can handle errors smoothly without crashing or causing adverse effects. If the system lacks adequate exception handling mechanisms, it may fail to recover gracefully, leading to performance issues or system failures.

The "RAISE" command in SQL is used to raise a custom error message in a query. It allows developers to handle exceptional scenarios by providing meaningful error messages.

Test Coverage Test coverage refers to the extent to which the software under test has been exercised by tests. It helps stakeholders understand which parts of the software have been tested and which have not. This metric is crucial in determining the effectiveness of the testing process and identifying areas that may require additional testing efforts to improve overall software quality.

In a CI/CD context, the build pipeline orchestrates the steps necessary to compile code, run tests, and deploy changes. Specifically, regarding database testing, it ensures that database updates are deployed smoothly and efficiently, allowing for rigorous testing before deployment, thereby enhancing the reliability of the overall system.

The immediate action to mitigate the security risk is to restrict access privileges. This involves revising the permissions assigned to the user to ensure they only have access to the data and features necessary for their role. Implementing proper access controls helps prevent unauthorized access to sensitive information.