Unit Testing on a c code which writes on files in a particular directory

Question

I've written a C code which takes a path to a directory and a string s. After opening the directory, the code looks for files with a particular extension and write the string given as a second argument to the last line of these files and a \n after it. This is all my function does (finding files with a particular extension and writing something at the end of the file). The C code for the function is done but I need to write some tests for the function using Cunit and I don't have any Idea how to write them. I've just written down what I want to test (below) but I don't know how to write them using Cunit. Can anyone help me with that? Thanks

• check if the user checks if the string 's' is nULL => segmentation fault
• check if bad address is given to the path argument of the function when there is no ".extension" file
• check if strcmp compares ".extension" and not "extension"
• check if the user uses == instead of strcmp to compare the extension
• check if the string 's' is written on a new line
• check the size of the string 's' sent to write => sent without \0 by strlen and the type is size_t
• check if the file is opened for writing (and not read only)
• check if string 's' is converted to void* before giving it to write function
• check if the return value of open ("fd") is checked
• check if the return value of opening a directory is checked (null or not)
• check if the return value of reading a directory is checked (null or not)
• check if the extension is checked (the string 's' is not added to all the files with other extensions
• check if the function ignores the '.' et '..' directories => DT_REG
• check if the file is closed after being opened
• check the return value of close
• check if the directory is closed after being opened
• check the return value of the directory

Answer 1

Unit tests are a kind of driver functions (i.e. like main() )for your code i.e. consider you have written a function foo. In foo you have to handle each thing/case properly.

Once you are done with it, you need to verify it with a Unit test which will pass different arguments to foo and let you know if every thing working properly or not.

check if the user checks if the string 's' is nULL => segmentation fault

check if bad address is given to the path argument of the function when there is no ".extension" file

check if strcmp compares ".extension" and not "extension"

etc. this kind of checks are supposed to be written in your function foo

Consider the example.

int divide(int numerator, int denominator) {

if (denominator == 0)
      return -1; 
else 
      return numerator/denominator;
}

In code you have done checking yourself. Now you would have to verify it with some Unit test framework or any other driver function like

void main(void) {

/* Pass correct arguments and expect it will return positive */ 
assert(divide(10, 2) > -1);
printf("Test passed for correct arguments\n");


/* Pass wrong arguments and expect it will return -1 */ 
assert(divide(10,0) == -1); 
printf("Test passes for wrong arguments\n);

}

In failure of your expected values, test would fail and your divide function is not correct. Hope this will help you.