How can you use boundary value analysis to test web APIs and services?

If your web API accepts a numeric parameter that ranges from 1 to 100, the boundary values are 1, 100, 0, and 101. These values are also called equivalence class partitions, because they divide the input or output domain into subsets that are expected to behave similarly.

Boundary value analysis for web APIs involves testing at the extreme ends of input ranges. For example, if an API accepts a numerical input between 1-100, test with values like 0, 1, 2, 99, 100, and 101. This helps identify any edge case issues that might cause the API to fail.

This technique can also increase coverage and effectiveness by checking the functionality and robustness of your web APIs and services at the edge cases. Moreover, it can detect and prevent potential errors or failures that could affect the quality and performance of your web APIs and services, ultimately saving time

One thing I've found helpful is checking for Boundary Errors: Pay close attention to how the API handles boundary values. Look for any unexpected behaviors or errors such as crashes, timeouts, or error messages revealing sensitive information. These could indicate potential security vulnerabilities.

Boundary value analysis is a testing technique that involves examining the critical and boundary values of an input to identify any errors or anomalous behavior in the system. This technique can also be applied to API and web service testing to ensure that the system correctly handles extreme situations or borderline values. Analyze the inputs used by APIs and web services and identify those that are critical to the system's operation. These may include parameters, input values, or particular input conditions that can influence the behavior of the system. By using boundary value analysis to test your APIs and web services, you can identify and resolve any boundary value management issues in your system.

APIs and services, you should first identify the input or output parameters with a defined range or limit, and determine the boundary values for each parameter. You should then design test cases that cover each boundary value and its expected result, execute the test cases, and compare the actual results with the expected results.

If the web service returns the correct monthly payment for each combination of boundary values and an error message for any invalid values. Additionally, if you have an API that validates an email address, you can design test cases to check if it returns true for each valid email address and false for each invalid email address.

For example, you should use a test design tool or spreadsheet to document and organize your test cases and results. Additionally, a test automation tool or framework can be employed to execute and verify your test cases.