Byebug is a simple to use, feature rich debugger for Ruby 2. It uses the new
TracePoint API for execution control and the new Debug Inspector API for call
stack navigation, so it doesn't depend on internal core sources. It's developed
as a C extension, so it's fast. And it has a full test suite so it's reliable.

It allows you to see what is going on _inside_ a Ruby program while it executes
and offers many of the traditional debugging features such as:

* Stepping: Running your program one line at a time.
* Breaking: Pausing the program at some event or specified instruction, to
  examine the current state.
* Evaluating: Basic REPL functionality, although [pry] does a better job at
  that.
* Tracking: Keeping track of the different values of your variables or the
  different lines executed by your program.