Suppose you have a program that takes as its input an intege

Suppose you have a program that takes as its input an integer from 0 to 423. Using the black box method of testing, list 9 list integers that you would use to adequately test the program.

Solution

In black box testingwhen you have any range of values as input, It is always good to go with boundary value analysis. In Boundary value analysis black box testing testcases are created using the boundary values.
So for given problem with range 0 to 423 (assuming inclusive), following values would do boundary analysis:(-1,0,1,422,423,424).
For rest of the testing you can follow other techniques like
Equivalence partitioning. In this technique we divide the input data(range) into partitions of equal sized data from which we create test.
For example in range 0 to 423 (assuming inclusive) we divide into 2 input sets (0-216)(217-423) and if we do boundary value analysis on these sets, the test integers would be (-1,0,1,215,216,217,422,423,424). However there are no fixed answers to this question because the middle test integer can vary depending on what testing technique you choose. But initial points (-1,0,423,424) would be there in every answer.