Software Testing – Grey Box Testing

Grey Box Testing – Introduction

Simply put, grey box testing is a combination of black box and white box testing. Grey box testing will cover both front end and back-end testing of a software application. For the front end testing, no programming knowledge is required whereas with the back-end it is required.

Grey box testing is a technique for testing a software application for those who have some understanding of the internal workings of the application.

The aim of grey box testing is to find errors caused by code structure or improper use of the system. Grey box testing is used as it combines the skills of both the testers and developers.

Grey Box Testing – Applications

Grey box testing is useful for a range of cases, such as:

• Integration Testing – This is where system modules are combined and tested together. Grey box testing allows for test cases to be designed specifically for these kinds of integration.
• Penetration Testing – Penetration testing is used to check the security of a system. The combination of front and back end in grey box testing really helps with this.

Grey Box Testing – Techniques

As with the other testing methodologies, there are certain testing techniques that are used with for grey box testing. They are:

• Matrix Testing
• Regression Testing
• Orthogonal Array Testing
• Pattern Testing

Grey Box Testing – Matrix Testing

Matrix testing is a technique for getting rid of unused variables in application code by actually identifying what variables are used. The developers would have defined the variables in an application, and the matrix testing will take care of cleansing these.

Grey Box Testing – Regression Testing

Regression testing is a type of testing that is carried out after changes, fixes or upgrades have been made to a system to ensure that the change has not affected the existing functionality of that system.

Grey Box Testing – Orthogonal Array

Orthogonal array testing is a technique used to identify any dysfunctional logic in a software application.

Grey Box Testing – Pattern Testing

Pattern testing is a technique that analyses previous errors that were found in the software to find out how they were caused.  This technique of testing is useful for formulating test cases going forward as the root of the defects are better understood. These test cases can be applied to software and modules that follow a similar design pattern.

Grey Box Testing – Advantages

There are a certain advantages that can be gained from grey box testing:

• Grey box testing is more focused on the user’s perspective of the system.
• The testers do not necessarily have to have a high level of programming skills in order to carry out the testing.
• Grey box testing is mostly a non-intrusive way of testing a software application.
• It is a very effective way of doing integration testing.
• The benefits of both black box and white box testing are gained through grey box testing.
• Grey box testing is usually not biased.

Grey Box Testing – Disadvantages

• Grey box testing is not usually suitable for testing distributed systems.
• It is not possible to test algorithms through grey box testing as access to the absolute logic in the code is not allowed.
• Grey box tests cases could have already been carried out by a software developer, thus making them unnecessary.
• The downsides of both black box testing and white box testing will be experienced when adopting the grey box approach.