Gray/Grey Box Testing

Niral Modi

July 31, 2013

Grey Box Testing is the high-level software testing method and a mixture of white box and black box testing methods. It not only determines the problem or error, but it also resolves the exact happening for the error. It gives an idea to a developer where exactly the error was and why it caused. Its main purpose is to determine the terrible implementation of the system under testing.

Gray Box testing is based on the concept of the end user view test. Testing is conducted from the user point of view. It involves a limited series of inputs plus outputs to conduct the test. After that, the test is performed based on the internal working of software architecture, algorithm view, program description and a lot more.

Following two types of issues can be encountered while conducting grey-box testing:

• Test execution is in constant flow but the content of the output is not correct. Somewhere in the system, data is processed incorrectly and system thus generates an error in showing results.
• Any failure due to uncertain reasons and thus process is aborted.

There are several advantages of using Gray-Box approach for software testing:

• It gives benefits of both White box plus Black box testing.
• Testers depend on functional requirements and interface definition while testing application.
• No source code/binary code testing is required.
• Limited information is available to tester so best-case scenarios can be developed around data type handling and protocols for communication in the program.
• Testing is not merely focused on web designing test.
• End users, Developers and Testers; can conduct gray box testing.
• Tester manage test scenario including communication protocol, data type and exception handling, Data Flow Diagrams (DFDs) and High-level Database diagrams.
• Data domain if provided can be tested along with internal boundaries.

Consider the example where you have to test simple email authentication web form. Email validation that happens at client side using JavaScript; is to be checked. If implementation details are provided than few assumptions can be made such as:

• Server will never receive invalid Email ID.
• Server will not send mail to invalid email ID.

Now performing gray box test, test case will be prepared considering that client has disabled JavaScript on the browser. With the failure of system assumptions made previously, following scenario can be presented:

• Server will receive invalid email ID.
• Server will send mail to invalid email ID.

The Gray Box method techniques:

• Matrix Test: Determine the status report for the application.
• Regression & Pattern Test: Repeat test cases when new changes are done.
• Orthogonal Array Test: Used for every possible combination.

Puzzle in the mind will be that why it is named “Gray” testing. Here is the solution to your puzzle. It is named “Gray” box testing approach because when the testertest the application; partial working of internal system of software will be known; but it is not known completely so the name gray box comes in existence. For testingmost of the web service application as well as business domain functionality, “Gray Box” testing approach is widely used.