Exercise 1-11. How would you test the word count program? What kinds of input are most likely to uncover bugs if there are any ?

/* Exercise 1-11. How would you test the word count program? What kinds of input are most likely to uncover bugs if there are any ? */

#include <stdio.h>
#define IN 1        /* inside a word */
#define OUT 0       /* outside a word */

/* count lines, words, and characters in input */

int main()
{
    int c, nl, nw, nc, state;
    state = OUT;
    nl = nw = nc = 0;

    while ((c = getchar()) != EOF) 
    {
        ++nc;
        if (c == '\n')
            ++nl;
        if ((c == ' ') || (c == '\n') || (c == '\t'))       /* (c = '\t') is changed to (c == '\t') to solve the bug. */
            state = OUT;
        else if (state == OUT)
        {
            state = IN;
            ++nw;
        }
    }
    printf("%d %d %d\n", nl, nw, nc);

    return 0;
}