This is where knowing how things happen under the hood, so to speak, help with understanding how to write proper code.
Let's take a look at what you're doing:
The program first prompts you for a value. The input buffer is empty. You didn't enter anything, yet, so it asks you for a value. You enter '1' and then press Enter. Here's what the input buffer looks like now:
getchar() grabs the first char you typed, which is the '1', and that's why it prints "Testing 1". Now it loops and it tries to read another selection. The input buffer looks like this:
So getchar() doesn't ask you for another character. It's already got one in the buffer. So it selects the '\n'.
This is why you have "Invalid Selection", because it's reading the '\n' as your input.
You repeat the same things with 2 and 3 later on.
A hackish solution is to just perform a double getchar(). The problem with that is if you have a dumb user that wishes to type a book. Consider if the user enters this:
The buffer starts out looking like this:
"It was the best of times and the worst of times..."
This is obviously going to cycle for awhile telling the user they entered invalid entries.
'I', t', ' ', 'w', 'a', 's'....
So what you could do is have an extra int called c. Call getchar() to read the user's first value like you normally do, and then run this line:
This will keep reading from the input buffer until either '\n' or EOF is reached and get the input lined up for the next entry.
while(((c = getchar()) != '\n') && (c != EOF));