When working with variables in an expression, what types of test cases should be created?

In the context of working with variables in an expression, creating a comprehensive set of test cases is crucial for ensuring that the expression behaves as expected under various conditions. Selecting a valid value, an invalid value, and a null value is the best practice, as it allows for thorough testing of the expression's logic.

A valid value is important because it verifies that the expression works correctly when given input that meets all criteria and expectations. This shows that the basic functionality operates as intended.

An invalid value tests the robustness of the expression by ensuring that it can handle incorrect or unexpected input gracefully. This helps identify whether appropriate error handling is in place, thus confirming that the system behaves predictably even when faced with invalid data.

Including a null value is essential as it checks how the expression deals with the absence of input. Null cases can reveal any potential issues that arise when variables are not set or when optional data is omitted, which is common in real-world applications.

Together, these three types of test cases provide a well-rounded approach to validating the performance and reliability of expressions in Appian, ensuring that they are equipped to handle a range of possible inputs.