When testing using boundary value analysis, which of the following would be considered an invalid input?

In the context of boundary value analysis, which focuses on testing values at the edges of valid input ranges, a score of -1 is considered an invalid input because it typically falls outside the permitted range for scores. For example, if the valid score range is established as 0 to 100, any value below 0, such as -1, would not be acceptable and should not be processed by the system.

Boundary value analysis is effective because defects are often found at the boundaries of input ranges. Thus, recognizing invalid inputs, such as -1, helps in designing test cases that thoroughly evaluate how the system handles extreme or out-of-range values. Testing with such inputs allows testers to ensure that the system can appropriately reject or handle inputs that are out of the specified limits.

In contrast, the other scores (50, 60, and 90) would likely be considered valid based on a conventional range for scores, which shows why they do not qualify as invalid inputs within this specific testing method.