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Continued from page 1
 Unit tests enable refactoring as well. After each small change the unit tests can verify that a change in
structure did not introduce a change in functionality.
Building a single universal
unit test suite for validation and regression testing enables frequent integration.
It is possible to integrate any recent changes quickly then run your own latest version of the test suite. When
a test fails your latest versions are incompatible with the team's latest versions. Fixing small problems every
few hours takes less time than fixing huge problems just before the deadline. With automated unit tests it is possible
to merge a set of changes with the latest released version and release in a short time.
Often adding new functionality
will require changing the unit tests to reflect the functionality. While it is possible to introduce a bug in both
the code and test it rarely happens in actual practice. It does occasionally happen that the test is wrong, but
the code is right. This is revealed when the
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problem is investigated and is fixed. Creating tests independent of code, hopefully before code, sets up checks
and balances and greatly improves the chances of getting it right the first time.
Unit Tests provide a safety
net of regression tests and validation tests so that you can refactor and integrate effectively. As they say at
the circus; never work without a net! Creating the unit test before the code helps even further by solidifying
the requirements, improving developer focus, and avoid creeping elegance. 
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