Testing and Debugging

Assertions

Functions often contain implicit assumptions (denominators should be nonzero, salaries should not be negative).
Such illegal values can creep into a program due to an input or processing error - with distressing regularity!

Assertions provide a valuable sanity check.

void raise_salary(Employee& e, double by)
{
   assert(e.get_salary() >= 0 );
   assert(by >= -100);
   double new_salary = e.get_salary() * (1 + by / 100);
   e.set_salary(new_salary);
}

If an assertion is not satisfied, the program terminates with a useful error message showing the line number and the code of the failed assertion:
```
assertion failed in file finclac.cpp line 61: by >= -100
```

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