Asserting Pre-Condition And Invariants
^^^^^
**Definition:**

* Using the same API to express pre-conditions (i.e. argument validation), post-conditions, invariants, and assertions.


**Code Example:**

.. code-block:: csharp

  public void Parse(string input) {
    // pre-condition
    Debug.Assert(input != null, "invalid argument");
    ...
    // invariant
    Debug.Assert(condition, "this should not happen");
  }

**References:**

.. admonition:: Quality attributes

    * :octicon:`file-code;1em` -  Code Example
    * :octicon:`comment-discussion;1em` -  Cause and Effect
    * :octicon:`graph;1em` -  Frequency
    * :octicon:`sync;1em` -  Refactoring

* `Parameterized Test Patterns For Effective Testing with Pex <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.159.6145&rep=rep1&type=pdf>`_ :octicon:`file-code;1em` :octicon:`comment-discussion;1em` :octicon:`sync;1em`