Friday, 8 February 2002

Test Conditions

Test Conditions are statements of compliance which testing will demonstrate to be either true or false. These are (in effect) test requirements.

Conditions serve different purposes. Some conditions will act as the audit reason for a particular test case e.g. The user must be able to create a flight. The tester will create a test which creates a flight, obviously there are more attributes to this case than this - what type of flight, what type of user, fully booked, partially booked, etc. These attributes are other types of conditions.

Some conditions are used to define a test’s attributes or preconditions. E.g. create flight of type local, create flight of type international.

Or are they....

This may be modelling that has not gone far enough.

The initial condition 'create a flight' is valid. When we only have test conditions as our modelling tool then we have to represent this as a condition. It is also a program function - create flight, or an object method, or an entity event, or a business process. Consequently we should really have a model and a derivation strategy that says “there must be at least one test for each entity event” or “there must be at least one test for each object method”. In this case it is obvious that “one test” will not cover the condition but with a rich model, with object or entity models we have a list of properties or attributes, these will have scoping variants (i.e. attribute flightType - international, local).

Basically, we use these context rich models to give us the combination information that we require to construct test cases. Without this approach we will never know if we have a valid or complete set of condition combinations.

Hierarchical models are appropriate for test grouping i.e. tests related to business processes, program modules, program functions etc. There is no reason why a test cannot be in more than one test grouping.

Hierarchical models are appropriate in derivation for hierarchical structures (it is possible to list entities attributes and events as hierarchical structures but this hides valid combination options and is a mix of ELH and ER, we should really have a relationship section on the model)

e.g.


  • Entity: Flight
    • Attribute: Type
    • Attribute: Start Airport
    • Event: Create
    • Event: Takeoff
    • Event: Land
    • Event: Delete

Models for test derivation should be rich. This allows a derivation strategy to be created which can be used to gauge the completeness of the test products and the validity of the test products.

With rich models, Test conditions become requirements which are used to check the completeness of the test derivation approach rather than the audit reason - unless of course there is no way to make the construction of test cases automatic with the implicit cross referencing of test conditions i.e. we don’t have to state ‘Create a flight’ as a test condition because there is an entity event on flight called create which we know we have to be able to test and it will apply to a variety of attributes on that entity. Without this rich modelling, and without an implicit (or strategy driven) approach to testing, a vast number of test conditions have to be created and maintained and no guarantee of combination thoroughness can be achieved.

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