TL;DR

This post gives and explains definition of Glass Box Software Testing approach that is given by Black Box Software Testing Foundations course (BBST) created by Rebecca Fiedler, Cem Kaner and James Bach.

The Problem

You are young and talented software tester in Agile team, and you were asked to use Glass Box Software Testing approach because you were a developer before. But what is glass box software testing approach?

Definition

Testing or test design using knowledge of the details of the internals of the program (code and data).

Explanation

Glass is used because of its transparency feature. Software tester can see through the product “box”.

New software testers usually forgot about product data. They only think how to test product features. But those features operate on data, and varying testing data, you can get different outcomes of features that your are testing.

In order to design tests, glass box software tester asks following question:

Does this code do what the programmer expects or intends?

Example is calendar function. Does this function takes into account leap years?

It is important to contrast this question with question asked by black box software tester:

Does this do what the users (human and software) expect?

Example is log in feature. User wants to log in as less as possible.

Glass box software testing is often called “white box”, to contrast it with “black box” software testing.

The glass box software tester becomes an expert in the implementation of the product under test.