Could be tests for a parser to convert it from string to object.

Not like your end users are going to type each piece into a separate field.

i think you think that telephone numbers are well-structured. they are not. they are messy. they do not fit a certain schematic.

I recommend also the following topic: "people have names". https://www.kalzumeus.com/2010/06/17/falsehoods-programmers-believe-about-names/

Names do not in general fit into the schematic "first name, last name"

You absolute buffoon. How do you figure this code isn't testing how to parse a string into such an object??

Found the Java programmer...

Better than an integer at least.

"The number" is itself two parts hence the dash. The first section being the prefix and the last part being the line number.

You seem to enjoy overengineering your code, don't you?