Chapter 1 - A Tutorial Introduction 11

Answer to Exercise 1-11, page 21
Solution by Dann Corbit
How would you test the word count program? What kinds of input are most likely to uncover bugs if there are any?

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It sounds like they are really trying to get the programmers to learn how to do a unit test. I would submit the following:

0. input file contains zero words
1. input file contains 1 enormous word without any newlines
2. input file contains all white space without newlines
3. input file contains 66000 newlines
4. input file contains word/{huge sequence of whitespace of different kinds}/word
5. input file contains 66000 single letter words, 66 to the line
6. input file contains 66000 words without any newlines
7. input file is /usr/dict contents (or equivalent)
8. input file is full collection of moby words
9. input file is binary (e.g. its own executable)
10. input file is /dev/nul (or equivalent)

66000 is chosen to check for integral overflow on small integer machines.

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Dann suggests a followup exercise 1-11a: write a program to generate inputs (0,1,2,3,4,5,6)

 

I guess it was inevitable that I'd receive a solution for this followup exercise! Here is Gregory Pietsch's program to generate Dann's suggested inputs:

#include <assert.h>
#include <stdio.h>

int main(void)
{
    FILE *f;
    unsigned long i;
    static char *ws = " \f\t\v";
    static char *al = "abcdefghijklmnopqrstuvwxyz";
    static char *i5 = "a b c d e f g h i j k l m "
                      "n o p q r s t u v w x y z "
                      "a b c d e f g h i j k l m "
                      "n o p q r s t u v w x y z "
                      "a b c d e f g h i j k l m "
                      "n\n";

    /* Generate the following: */
    /* 0. input file contains zero words */
    f = fopen("test0", "w");
    assert(f != NULL);
    fclose(f);

    /* 1. input file contains 1 enormous word without any newlines */
    f = fopen("test1", "w");
    assert(f != NULL);
    for (i = 0; i < ((66000ul / 26) + 1); i++)
        fputs(al, f);
    fclose(f);

    /* 2. input file contains all white space without newlines */
    f = fopen("test2", "w");
    assert(f != NULL);
    for (i = 0; i < ((66000ul / 4) + 1); i++)
        fputs(ws, f);
    fclose(f);
 
    /* 3. input file contains 66000 newlines */
    f = fopen("test3", "w");
    assert(f != NULL);
    for (i = 0; i < 66000; i++)
        fputc('\n', f);
    fclose(f);
 
    /* 4. input file contains word/
     *    {huge sequence of whitespace of different kinds}
     *    /word
     */
    f = fopen("test4", "w");
    assert(f != NULL);
    fputs("word", f);
    for (i = 0; i < ((66000ul / 26) + 1); i++)
        fputs(ws, f);
    fputs("word", f);
    fclose(f);

    /* 5. input file contains 66000 single letter words,
     *    66 to the line
     */
    f = fopen("test5", "w");
    assert(f != NULL);
    for (i = 0; i < 1000; i++)
        fputs(i5, f);
    fclose(f);

    /* 6. input file contains 66000 words without any newlines */
    f = fopen("test6", "w");
    assert(f != NULL);
    for (i = 0; i < 66000; i++)
        fputs("word ", f);
    fclose(f);

    return 0;
}