How can you design an effective test case for a safety-critical system?

1 Define the test objectives

The first step in designing a test case is to define the test objectives, which are the goals and outcomes the test case aims to achieve. The objectives should be aligned with the system's requirements, specifications, strategy, and plan. Additionally, they should be clear, measurable, and verifiable so that they can be used to evaluate the test results and determine success or failure. Examples of test objectives include verifying that the system meets functional and non-functional requirements, validating that it behaves as expected under both normal and abnormal conditions, detecting any defects or errors in the system, assessing its robustness, security, and performance, as well as demonstrating compliance with standards and regulations.

3 Design the test cases

The next step in designing a test case is to create the detailed descriptions of the steps and actions to execute the test scenarios. These test cases should include the test inputs, expected outputs, preconditions, postconditions, and verification methods for each test scenario. Additionally, the test cases should specify the test data, tools, procedures, and scripts that will be used. For example, for a normal operation test case, the input is a valid command to start the system, the expected output is a confirmation message, the precondition is that the system is powered off and ready to start, and the postcondition is that the system is powered on and operational. The verification method would be to compare the output message with the expected message. The test data would be a valid command, the tool would be a user interface or terminal, the procedure would involve entering the command and observing the output, and finally, the script would be start_system() . Another example of a test case would be a stress situation. The input here would be a high number of concurrent requests to the system, with an expected output of processing those requests and displaying results. The precondition for this case would be that the system is powered on and operational; whereas, its postcondition would be that it remains operational and responsive. To verify this case, one should check both response time and accuracy of results. The test data here would be a high number of requests; while its tool would be either a load generator or simulator. The procedure involves generating requests and observing results; as for its script - load_test() . Reporting and documenting these tests will help inform stakeholders as well as provide valuable insights for improving cloud security posture.

5 Design the test coverage

The final step in designing a test case is to design the test coverage, which is the measure of how well the test case covers the system's functionality and behavior. This coverage should ensure that all relevant and important aspects of the system, such as features, functions, components, interfaces, paths, branches, conditions, and scenarios are tested. The test coverage should also take into account potential risks and hazards of the system and prioritize test cases that address the most critical and likely ones. Examples of criteria that can be used for test coverage include requirement coverage, function coverage, component coverage, interface coverage, path coverage, branch coverage, condition coverage, and scenario coverage. By using these criteria for test coverage, you can ensure that your tests are comprehensive and effective.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?