Try a program with several examples. Compare what it does with what you want.
Try a program with several examples, not just one. One good try is only one try.
Write down the answer you want first, so a mismatch is easy to spot.
Pick small numbers, big numbers and zero.
Compare what you want with what you get. When they do not match, that is how you spot a bug.
These are some of the questions on the sets. The printable sheets have more and an answer key.
Yes. Six doubled is 12.
No. Eight doubled is 16, but the machine gave 10.
One example can hide a bug. The add-two machine gave the right answer for two, and was wrong for most numbers.
5, and we want 6. 3 + 2 = 5, but three doubled is 6.
Small numbers, big numbers and zero. Different numbers catch bugs that one example can hide.
Think of a rule together, like add three or double it. One of you is the machine. The other says numbers, and the machine answers by the rule. Try a small number, a big number and a zero before you guess the rule. Then swap!
Play the Mission: think of a secret number rule together, like add three or double it. One of you is the machine, and the other says numbers. Try a small number, a big number and a zero before guessing the rule, then swap.
