White-box and black-box testing

White box and black box testing are terms used to describe the point of view a test engineer takes when designing test cases. Black box being an external view of the test object and white box being an internal view. Software testing is partly intuitive, but largely systematic. Good testing involves much more than just running the program a few times to see whether it works. Thorough analysis of the program under test, backed by a broad knowledge of testing techniques and tools are prerequisites to systematic testing. Software Testing is the process of executing software in a controlled manner; in order to answer the question “Does this software behave as specified?” Software testing is used in association with verification and validation. Verification is the checking of or testing of items, including software, for conformance and consistency with an associated specification. Software testing is just one kind of verification, which also uses techniques such as reviews, inspections, and walk-throughs. Validation is the process of checking what has been specified is what the user actually wanted.

• Validation: Are we doing the right job?
• Verification: Are we doing the job right?

In order to achieve consistency in testing, it is imperative to have and follow a set of testing principles. This enhances the efficiency of testing within SQA team members and thus contributes to increased productivity.

There are generally 3 main levels of software testing carried out:

• Unit Testing: in which each unit (basic component) of the software is tested to verify that the detailed design for the unit has been correctly implemented
• Integration testing: in which progressively larger groups of tested software components corresponding to elements of the architectural design are integrated and tested until the software works as a whole.
• System testing: in which the software is integrated to the overall product and tested to show that all requirements are met

A further level of testing is also done, in accordance with requirements:

• Acceptance testing: upon which the acceptance of the complete software is based. The clients often do this.

Changes made in order to fix bugs or develop further fucntionality may cause previously successful tests to fail, so regression testing is used to repeat the earlier successful tests to ensure that changes made in the software have not introduced new bugs/side effects.

In recent years the term grey box testing has come into common usage. The typical grey box tester is permitted to set up or manipulate the testing environment, like seeding a database, and can view the state of the product after his actions, like performing a SQL query on the database to be certain of the values of columns. It is used almost exclusively of client-server testers or others who use a database as a repository of information, but can also apply to a tester who has to manipulate XML files (DTD or an actual XML file) or configuration files directly, or perform testing like SQL injection. It can also be used by testers who know the internal workings or algorithm of the software under test and can write tests specifically for the anticipated results. For example, testing a data warehouse implementation involves loading the target database with information, and verifying the correctness of data population and loading of data into the correct tables.