Testing prototypes in DSDM

DSDM prototype serves two different roles:

  • it is a partial build of the system that will be delivered
  • it is a technique for gathering information to clarify functional or non-functional requirements.
Different test criteria apply depending on the role the prototype is serving:
  • To the extent that the prototype represents part of the functionality of the final system, a test pass/fail can be based on whether or not the test result from the prototype matches an expected result based on the known  requirements.
  • To the extent that the prototype is intended to clarify requirements, the criterion for test success or failure is whether or not the prototype generates the expected information. This is exploratory. The expected
    information cannot be predefined in the same way that an expected result can be. The test of the prototype is being used to expand the knowledge and understanding of the prototype builder. The test is successful if this
    is achieved in the area under investigation.

A single prototype may serve in both roles and therefore should be tested against both criteria.In the Functional Model and Design and Build Iteration phases, prototyping generally iterates up to three times in line with the timeboxing process.  The prototypes that are produced can fall within any one of four categories. Prototypes of all categories can be tested against a mixture of “expected result” and “expected information” criteria.

This iterative lifecycle is summarised in the table below, which shows the categories of prototype and the type of testing criteria that will tend to apply at each iteration.

Iteration within Timebox
Prototype Category Investigation Refinement Consolidation
Business EI EI/ER ER
Usability EI EI/ER ER
Performance EI EI/ER ER
Capability EI EI/ER ER
Testing criteria for the categories of prototype (EI = Expected Information, ER = Expected Result)

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