Debugging with pry and byebug in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output when using pry to inspect a variable?

Consider the following Ruby code snippet using pry. What will be printed when the program hits the binding.pry line and you type x in the pry console?

Ruby

require 'pry'
x = 10
binding.pry
puts "Done"

A 10

B nil

C Error: undefined local variable or method `x`

D Nothing is printed

💡 Hint

Remember that binding.pry pauses execution and lets you inspect variables in the current scope.

When the program pauses at binding.pry, you can type x to see its value, which is 10.

❓ Predict Output

intermediate

What happens when byebug hits a breakpoint?

Given this Ruby code using byebug, what will be the output when the program pauses at byebug and you type y + 5 in the debugger console?

Ruby

require 'byebug'
y = 7
byebug
puts y + 3

A 10

B 12

C Error: undefined local variable or method `y`

D Nothing, program continues without pause

💡 Hint

Byebug pauses execution and lets you evaluate expressions in the current context.

At the byebug line, the program pauses. Typing y + 5 evaluates to 12 because y is 7.

❓ Predict Output

advanced

What error does this code raise when using pry incorrectly?

What error will this Ruby code raise when run?

Ruby

require 'pry'
Pry.start
x = 5

A No error, program runs fine

B RuntimeError: Pry session already started

C NoMethodError: undefined method `start` for Pry:Module

D SyntaxError: unexpected end-of-input

💡 Hint

Check if Pry.start is a valid method call.

Pry.start is not a defined method. The correct way to start a pry session is binding.pry.

❓ Predict Output

advanced

What is the output after continuing from a byebug breakpoint?

Given this Ruby code, what will be printed after you type continue in the byebug console?

Ruby

require 'byebug'
x = 3
byebug
x += 4
puts x

A 7

B Nothing, program stuck at breakpoint

C Error: undefined local variable or method `x`

D 3

💡 Hint

After continuing, the program runs the next lines normally.

After continue, x becomes 7 and is printed.

🧠 Conceptual

expert

Which option correctly explains the difference between pry and byebug?

Choose the best explanation of how pry and byebug differ in Ruby debugging.

A Pry only works with Rails apps; byebug only works with Ruby scripts.

B Pry and byebug are identical tools with different names.

C Pry is used for performance profiling; byebug is used for syntax checking.

D Pry is an interactive REPL allowing live code inspection and modification; byebug is a step-by-step debugger focused on breakpoints and stepping through code.

💡 Hint

Think about how each tool lets you interact with running code.

Pry provides a powerful interactive shell to inspect and modify code live. Byebug is designed for setting breakpoints and stepping through code execution.