There really is a difference  . . .

There really is a difference . . .

Classic software development techniques follow a pattern of analysis, design, coding and testing. Regardless of whether the process is driven by a big upfront design or incremental design decisions, code is written and then tests are executed for the first time. Test plans, scenarios and cases may well be developed in parallel with code (generally only with a minimum of interaction), however execution only occurs as code is completed. In test-last models, the roles of developer and tester are typically filled by professionals with very different types of training and many times from separate management structures. The differences in training and management structure create structural communication problems. At best the developers and testers are viewed as separate but equal, although rarely do you see testers and developers sharing tables at lunch.

Testing last supports a sort of two tiered development environment apartheid in which testers and developers are kept apart. I have heard it argued that anyone that learned to write code in school has been taught how to test the work they have create, at least in a rudimentary manner, therefore they should be able to write the test cases needed to implement test-driven development (TDD). When the code is thrown over the wall to the testers, the test cases may or may not be reused to build regression suites. Testers have to interpret both the requirements and implementation approaches based on point in time reviews and documentation.

Test-first development techniques take a different approach, and therefore require a different culture. The common follow of a test first process is:

  • The developer accepts a unit of work and immediately writes a set of tests that will prove that the unit of work actually functions correctly.
  • Run the tests.  The tests should fail.
  • Write the code need to solve the problem.  Write just enough code to really solve the problem.
  • Run the test suite again.  The test should pass.

Most adherents of Agile development methods have heard of TDD which is the most common instantiation of the broader school of test-first development (TFD).  TDD extends TFD by adding a final refactoring step to the flow in which developers write the tests cases needed to prove that unit of work solves the business problem and is technically correct. Other variants, such as behavior-driven and acceptance test-driven development, are common.  In all cases the process follows the same cycle of writing tests, running the tests, writing the code, re-running the tests and then  refactoring the only difference being the focus tests.

TFD techniques intermingle coding and testing disciplines, creating a codependent chimera in which neither technique can exist without the other. For TFD to work most effectively coders and testers must understand each other and be able to work together. Pairing testers and developers together to write the test case either for component/unit testing (TDD), behavior-driven tests (BDD) or acceptance testing (ATDD) creates an environment of collaboration and communication.  Walls between the two groups will be weak, and over time, torn down.

Test-first development and test-last development techniques are different both in terms of the how work is performed and how teams are organized. TFD takes a collaborative approach to delivering value, while test-last approaches are far more adversarial in nature.

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