=Design by Contract for Ruby

This library supports Design by Contract for Ruby.

=Installation

Install the *rdbc* gem itself by the following command:

  $ gem install armin-joellenbeck-rdbc --source http://gems.github.com

=Usage

A a standard example for Design by Contract consider the following Stack
class and its contract StackContract.

  :include:spec/stack_spec.rb

The mechanics are really simple. There is the class Stack.
For instances of this class you can define a contract by subclassing
<b>DesignByContract::Contract</b>, in the example the contract is named
StackContract.
Then connect the class Stack to its contract StackContract by using the line
  contract StackContract
in the class definition of Stack.

Then the following happens when a method of a Stack instance is called:

1. the corresponding pre condition is called with the parameters:
   * the instance itself
   * the parameters of the method call

2. the method is called

3. the corresponding post condition is called with the parameters:
   * the instance before the method is called
   * the instance after the method is called
   * the return value of the method call
   * the parameters of the method call

4. the invariant is called with the parameters:
   * the instance before the method is called
   * the instance after the method is called

The instance before the execution of *method* in 3. and 4.
is in fact a copy of the instance before the execution. So you have to implement
the method *initialize_copy* in the class under contract, i.e. the class
Stack.

In any of these contract methods you can use assertions as in Test::Unit tests.
When an assertion fails, the exception Test::Unit::AssertionFailedError
is raised.

=Support

The project home is at
GitHub[http://github.com/armin-joellenbeck/rdbc/tree/master]:
http://github.com/armin-joellenbeck/rdbc/tree/master

Feel free to send:
* bug reports
* support requests
* feature requests
* patches

=Copyright

Copyright (c) 2007 - 2009 by Armin Jöllenbeck
<armin@joellenbeck.net[mailto:armin@joellenbeck.net]>

All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. The names of the contributors may not be used to endorse or promote products
   derived from this software without specific prior written permission.

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