Python...testing classes?

Question

In python, how do we write test cases for our classes? For example:

class Employee(object):
  num_employees = 0


# numEmployess is incremented each time an employee is constructed
  def __init__(self, salary=0.0, firstName="", lastName="", ssID="", DOB=datetime.fromordinal(1), startDate=datetime.today()): #Employee attributes
    self.salary=salary
    self.firstName = firstName
    self.lastName = lastName
    self.ssID = ssID
    self.DOB = DOB
    self.startDate = startDate
    Employee.num_employees += 1 #keep this 

  def __str__(self): #returns the attributes of employee for print
    return str(self.salary) + ', ' + self.firstName + ' ' + self.lastName + ', ' + self.ssID + ', ' + str(self.DOB) + ', ' + str(self.startDate)

I know there is something called unit testing. But I'm not sure how it works at all. Could not find a good explanation I understood online.

Answer 1

doctest is the simplest. Tests are written in the docstring, and look like REPL episodes.

 ...

  def __str__(self):
    """Returns the attributes of the employee for printing

    >>> import datetime
    >>> e = Employee(10, 'Bob', 'Quux', '123', startDate=datetime.datetime(2009, 1, 1))
    >>> print str(e)
    10, Bob Quux, 123, 0001-01-01 00:00:00, 2009-01-01 00:00:00
    """
    return (str(self.salary) + ', ' +
            self.firstName + ' ' + 
            self.lastName + ', ' +
            self.ssID + ', ' + 
            str(self.DOB) + ', ' +
            str(self.startDate)
            )

if __name__ == '__main__':
  import doctest
  doctest.testmod()