[TIP] TDD and automatic code generation

Andreas Dotzler andreas.dotzler at fs.ei.tum.de
Mon Sep 3 00:50:00 PDT 2007

This is about using Zope3 interfaces (or schemas) and doctest to develop in 
TDD fashion. I very much liked the article "Zope3 in 30 Minutes 
which is specific about developing a zope3 application, however the principle 
should hold for any python application. 

So the steps are: 
1. write the interface IClassName.py
2. write the doctest test_ClassName.py
3. implement the class ClassName.py and check if it passes the doctest

There is potential of supporting this development by automatic code 
generation. Using the Interface one could generate a template for the doctest 
+ the implementation. Here is a example

The interface IClassName.py

from zope.interface import Interface, Attribute
from zope.schema import TextLine 

class IClassName( Interface ):
    """The interface for ClassName

    attr1 = TextLine(
            title=u"Attribute 1",
            description=u"stores a string",
            default=u"my default value")

    def method1():
        """ doc of method1

This would lead to a test_ClassName.py that at least includes the following

This is the doctest for class ClassName

Verify Interface
    >>> from zope.interface.verify import *
    >>> from ClassName import ClassName
    >>> from IClassName import IClassname
    >>> verifyClass( IClassname, Classname )

Create an Instance
    >>> a = ClassName()

Check default value of Attribute 1, which stores a string
    >>> print a.attr1
    my default value

Run method1()
    >>> a.method1()
    result of method 1

[...maybe more...]

The base for an implementation would look like

from zope.interface import implements
from IClassName import IClassName

class ClassName( object ):
    """ClassName ....

    implements( IClassName )

    def __init__( self, attr1="my default value" ):
        self.attr1 = attr1

    def method1( self ):

    def _test():
        import doctest
        doctest.testfile( "test_NetworkHandler.py" )

    if __name__ == "__main__":

[...maybe more...]

One could think of many thinks for [...maybe more...] especially in case the 
schema defines some validation.

Does anyone know a concept, tool, script that does approximately what I 
suggest ? 
Any comment or remark highly appreciated.

Andreas Dotzler

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