Answer.

Background of the question

The "gray box" methodology emerged as a compromise between "black box" and "white box" testing, aiming to eliminate the limitations of these methods. It allows for partial knowledge of the internal structure of the system while verifying input and output data, thus gaining advantages from both techniques.

Problem

Often, tasks require knowing more than what user interfaces allow, but access to the complete source code is absent. The risk is under-testing important scenarios related to internal mechanisms without delving into architectural details like in a "white box".

Solution

This approach is applied when there is partial access to documentation, architecture, APIs, or services. It allows for identifying errors at the intersection of front-end and back-end as well as examining data processing within modules.

Key features:

Enables testing complex interactions between system modules.
Allows for creating effective scenarios to find complex bugs.
Reduces the risks of missing defects related to integration and logic.

Trick questions.

Is it possible to conduct gray box testing if you have no access to any documentation or code?

No. The gray box method assumes that the tester has at least partial information about the internal structure of the application. If you are working completely "blind", the "black box" method is used instead.

Is reviewing logs considered a form of testing using the "gray box" method?

Yes, if you analyze the logs to understand how the system processes incoming data, this can be considered an element of the "gray box" approach, as you are not limited to the user interface alone.

Can the gray box methodology be used for unit testing?

No. Unit testing is typically in the realm of "white box" testing, where full access to the code is required, and testers work specifically at the level of internal functions.

Common mistakes and anti-patterns

Attempting to completely obscure the internals of the system without having the necessary information.
Underestimating the need for architectural data.
Confusion between methodologies: misapplying the methodology in an inappropriate context.

Example from real life

Negative case

The tester attempted to apply the "gray box" technique based only on assumptions and UI testing, without examining the API or requesting the architectural diagram.

Pros:

Quick coverage of user scenarios.

Cons:

Missing internal errors between application layers.
Incorrect identification of bug causes.

Positive case

Before testing integration scenarios, the tester requested architectural diagrams from the team, studied the API endpoints, analyzed logs, and was able to identify a problem at the interaction layer between the back-end and front-end.