Testing & Laboratory

Functional Testing

A scope heading, not a single list of experiments; The following test families conduct the experiments.

Scope

Test families in Functional Testing

Functional Testingis a scope heading, not a single list of experiments. The following test families carry out the experiments in the scope; A complete list of each family is on its own page.

Functional Testing — What Does This Testing Field Cover?

The section below describes how the field of Functional Testing works. The conditions, sample requirements and acceptance criteria of the individual tests in this field are given on the relevant test pages.

Functional testing verifies that a product performs the functions it was designed for. It differs from performance testing: performance measures "how well", function answers "does it work".

The category takes very different forms according to product type. In a control unit it is verified that all input-output combinations respond correctly; in a domestic appliance that all programmes and modes work; in a medical device that alarm and safety functions activate; in software that the requirements are met.

Functional verification also runs inside ENVIRONMENTAL tests, and that is where its real value appears. Keeping a product in a temperature chamber and then switching it on shows only permanent damage; if the product is operated and monitored DURING the test, intermittent functional disturbances are caught. Faults of that kind generate the most complaints in the field.

The acceptance criterion in this category comes from the manufacturer. A standard does not know which of a product's functions are critical; the manufacturer defines which loss of function is unacceptable. In medical devices that definition is a formal requirement under the name "essential performance".

Use error is a separate axis: if a function works technically but the user misunderstands it, the outcome is still a failure. Usability evaluation addresses this question and is mandatory for medical devices.

Commonly confused in this field

If the product is not operated during an environmental test, intermittent functional disturbances remain invisible.
The acceptance criterion does not come from the standard; the manufacturer defines which function is critical.
Functional verification does not replace performance measurement.
A function that works technically may be misunderstood by the user; usability is assessed separately.

Which decisions these results support