Thanks! I've fixed tests to show the full error

Would you be so kind to clarify what is your expectation of a random test?
There are tests with different type of inputs in the Test Cases section that checks the solution, like "TomTind1" for example. Or did you mean that I needed to add such tests into Example tests section?

Could you please explain your thought? Are you talking about returning a string for the edge cases? I don't think it's an issue though.

It's there, please see the last line of tests section:

expect(convertStringToPhonebook('')).to.equal( "Phonebook is empty");

Hi, thank you. I've updated description. As for tests: there are 2 corresponding example tests related to the example, provided in the description, isn't it enough?

The description should also mention the character length of firstName & lastName , corresponding sample & example tests should also be added for clarity.

No sample tests and example tests for inputs with no arguments or empty strings

Having multiple output types is a bad practice.

No random tests.

expected [ Array(3) ] to deeply equal [ Array(3) ]