In the context of test tools, what are the typical roles of glass-box (white-box) testing tools compared to black-box testing tools?

Introduction / Context:
Testing tools can be categorized according to whether they require knowledge of the internal structure of the software or treat it as a black box. Glass-box, or white-box, testing tools operate with awareness of the code structure, while black-box tools interact only through public interfaces, screens or APIs. Understanding this distinction helps teams choose appropriate tools for different testing goals.

Given Data / Assumptions:

Glass-box tools may connect to source code, binaries or coverage frameworks to see which statements, branches or paths are executed.
Black-box tools drive the application through its user interface or API without access to internal details.
Both types of tools support testers and developers but in different ways.

Concept / Approach:
Glass-box testing aims to improve internal coverage of the code and detect structural weaknesses, such as untested error paths or unreachable code. Tools in this category include code coverage analyzers, unit test frameworks with instrumentation and static analysis tools. Black-box testing tools, such as GUI automation frameworks, API test tools and regression harnesses, focus on whether the system produces correct outputs for given inputs according to requirements, regardless of how it is implemented internally.

Step-by-Step Solution:
Identify that glass-box tools require access to source code or compiled code to calculate coverage and analyze internal structure. Note that black-box tools typically work by simulating user actions, sending API calls or comparing output against expected results. Option a clearly describes glass-box tools as analyzing internal structure and black-box tools as validating external behavior. Options b, c and d either misclassify the tools or deny meaningful differences, which contradicts standard testing knowledge. Therefore, option a is the correct characterization.

Verification / Alternative check:
In practice, teams often use a code coverage tool to evaluate the effectiveness of unit tests (glass-box) and a separate GUI or API automation tool to drive end-to-end tests (black-box). Documentation from tool vendors also uses these terms to describe their focus. This real-world usage confirms the explanation in option a.

Why Other Options Are Wrong:
Option b confuses different non functional testing types with structural classification; glass-box versus black-box is unrelated to usability versus performance.
Option c exaggerates tool capabilities, suggesting they can replace people, which is not accurate.
Option d denies the very distinction that these terms were created to express.

Common Pitfalls:
A common mistake is to rely only on black-box tests and ignore structural coverage, leaving parts of the code untested. Another pitfall is to focus solely on coverage numbers from glass-box tools without ensuring that tests validate meaningful behavior. A balanced test strategy uses both glass-box and black-box perspectives to improve confidence.

Final Answer:
Glass-box tools are mainly used to analyze and exercise internal code structure and measure coverage, while black-box tools are used to test external behavior, such as functional and GUI behavior, based on requirements and user scenarios.