Invoke a function and ensure that it returns the expected result.
Problems:
- you don't know what the result is supposed to be
- you can't automate the equality comparison
If you don't know what the result is supposed to be, hopefully
there are some sanity checks that can be performed to ensure that the
result is at least probably correct.
A typical example is ensuring that a message is printed to standard
output.
It's possible to capture standard output, but it's not reasonable for the
testing framework to require that the message printed be exactly the
same in all versions of the implementation.
However, it is possible to require that if the message is telling
some number to the user, that that number appear in the output.
If the result of the function is a complicated object, and it can be
specified exactly what that object should be, it seems reasonable to
implement that equality test.
If the equality problem can't be broken down into smaller fragments,
is the design right?
DesignForTestability includes the ability to check equality.
Expected Result