Difference between acceptance test and functional test?

Question

What is the real difference between acceptance tests and functional tests?

What are the highlights or aims of each? Everywhere I read they are ambiguously similar.

Answer 1

In my view the main difference is who says if the tests succeed or fail.

A functional test tests that the system meets predefined requirements. It is carried out and checked by the people responsible for developing the system.

An acceptance test is signed off by the users. Ideally the users will say what they want to test but in practice it is likely to be a sunset of a functional test as users don't invest enough time. Note that this view is from the business users I deal with other sets of users e.g. aviation and other safety critical might well not have this difference,

Answer 2

The relationship between the two: Acceptance test usually includes functional testing, but it may include additional tests. For example checking the labeling/documentation requirements.

Functional testing is when the product under test is placed into a test environment which can produce variety of stimulation (within the scope of the test) what the target environment typically produces or even beyond, while examining the response of the device under test.

For a physical product (not software) there are two major kind of Acceptance tests: design tests and manufacturing tests. Design tests typically use large number of product samples, which have passed manufacturing test. Different consumers may test the design different ways.

Acceptance tests are referred as verification when design is tested against product specification, and acceptance tests are referred as validation, when the product is placed in the consumer's real environment.

Answer 3

Acceptance testing:

... is black-box testing performed on a system (e.g. software, lots of manufactured mechanical parts, or batches of chemical products) prior to its delivery.

Though this goes on to say:

It is also known as functional testing, black-box testing, release acceptance, QA testing, application testing, confidence testing, final testing, validation testing, or factory acceptance testing

with a "citation needed" mark.

Functional testing (which actually redirects to System Testing):

conducted on a complete, integrated system to evaluate the system's compliance with its specified requirements. System testing falls within the scope of black box testing, and as such, should require no knowledge of the inner design of the code or logic.

So from this definition they are pretty much the same thing.

In my experience acceptance test are usually a subset of the functional tests and are used in the formal sign off process by the customer while functional/system tests will be those run by the developer/QA department.

Answer 4

The difference is between testing the problem and the solution. Software is a solution to a problem, both can be tested.

The functional test confirms the software performs a function within the boundaries of how you've solved the problem. This is an integral part of developing software, comparable to the testing that is done on mass produced product before it leaves the factory. A functional test verifies that the product actually works as you (the developer) think it does.

Acceptance tests verify the product actually solves the problem it was made to solve. This can best be done by the user (customer), for instance performing his/her tasks that the software assists with. If the software passes this real world test, it's accepted to replace the previous solution. This acceptance test can sometimes only be done properly in production, especially if you have anonymous customers (e.g. a website). Thus a new feature will only be accepted after days or weeks of use.

Functional testing - test the product, verifying that it has the qualities you've designed or build (functions, speed, errors, consistency, etc.)

Acceptance testing - test the product in its context, this requires (simulation of) human interaction, test it has the desired effect on the original problem(s).

Answer 5

They are the same thing.

Acceptance testing is performed on the completed system in as identical as possible to the real production/deployement environment before the system is deployed or delivered.

You can do acceptance testing in an automated manner, or manually.