Which of the following is an advantage in using a bottom-up versus a top-down approach to software testing?

A.
Interface errors are detected earlier.

B.
Errors in critical modules are detected earlier.

C.
Confidence in the system is achieved earlier.

D.
Major functions and processing are tested earlier.

Explanation:
Bottom Up Testing is an approach to integrated testing where the lowest level components are tested first, then
used to facilitate the testing of higher level components. The process is repeated until the component at the top
of the hierarchy is tested.
With Bottom Up Testing critical modules can be tested first and the main advantage of this approach is that
bugs are more easily found.
All the bottom or low-level modules, procedures or functions are integrated and then tested. After the
integration testing of lower level integrated modules, the next level of modules will be formed and can be used
for integration testing. This approach is helpful only when all or most of the modules of the same development
level are ready. This method also helps to determine the levels of software developed and makes it easier to
report testing progress in the form of a percentage.
Incorrect Answers:
A: Interface modules are located at higher levels of the software design, not at the bottom levels.
C: The major advantage of the top-down approach is that bugs are found earlier, not that confidence is
achieved earlier.
D: The major functions are not located at the bottom, and would not be tested earlier.

https://en.wikipedia.org/wiki/Integration_testing#Top-down_and_Bottom-up