Source Control, Build, Test

I believe that the three fundamental practices of Software Engineering are: source control, build and test.

To be more specific these practices mean:

• Source Control.  All artifacts required to build and deploy the software are in source control and developers are committing to the repository frequently (> 1 per day). This is straight forward, provided that an adequate tool is chosen and a simple branching strategy is adopted.  The branching strategy maintains a "trunk" where main development occurs, and branches when a release is made.  Maintenance of the release occurs in the branch.
• Build.  The build requires single action to execute, is run after each source control check-in and takes less than 10 minutes to execute.  This is straight forward to achieve but requires discipline and constant minor maintenance.  A continuous integration tool should be used to run the build.
• Test.  A comprehensive set of automated unit and automated acceptance tests are in place, which are run automatically as part of the build.  In practice this means adopting Test Driven Development [Beck] to develop unit tests.   For automated acceptance testing no general method has yet been developed. 

I have worked on a number of projects which adopted these practices to a greater or lesser extent. My experience is that the greater the adoption of these practices the "less painful" the project has been to work on.  None of the projects I have worked on has fully implemented all three practices. Most often we have failed to fully implement automated testing.  

This is because automated testing is difficult.