How does the White Box Test work?

Question

I read in this reply user’s utluiz the following description of the White Box Test, see:

White box test: when assessing the internal functioning of the software. For example, if certain methods perform correctly.

However, I still have doubts about this type of test.

Doubts

1. How the white box test is performed?
2. This test is related to only methods of a particular class?
3. What types of methods should I submit to the white box test?

^{I would like a practical example of a white box test being applied in a method, if possible.}

Answer 1

White box tests evaluated the behavior of a feature. Whether a given input will produce the expected output or whether code has passed the desired stream. To perform this type of test you need knowledge of the source code (other than a black box test where only the sample is evaluated).

1 . How the white box test is performed?

The most formal way to do this is to use a unit test battery and it is also possible to simplify by separating a portion of the code and create a new project/file for this purpose.

2. This test is related to only methods of a particular class?

No, the test can check whether a particular part has been executed or not, as well as can test an entire method.

Some unit testing tools provide test case-based diagnostics and tell which lines/snippets of code have not been executed, which serves as an indication that not all paths have been run or there is dead code.

3. What types of methods should I submit to the white box test?

Any type especially have some validation or application of business rule.