Several simple questions about nunit

1. Attributes of testfixture
The testfixture attribute indicates that a class has a test method, which is located under the nunit. Framework namespace.
Among them, there is a comment in his official file that the class must have a default constructor (this class must have a default constructor), but I found that it is not needed at all. You can compile and test it.

2. Since nunit is used for unit testing (I am not wrong ),CodeCapture exceptions inSource codeWhat is the relationship between write capture exceptions?

3. Make a simple investigation. Are there any companies using nunit on this blog?