Bundler for dependency resolution in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Bundler command?

You run bundle list in a Ruby project with a Gemfile containing gem 'rack', '~> 2.2'. What will Bundler display?

Ruby

bundle list

A

Gems included by the bundle:
  * rack (2.2.3)

B Could not find gem 'rack (~> 2.2)' in any of the sources

C Fetching gem metadata from https://rubygems.org/...

D Bundler version 2.3.0

💡 Hint

Think about what bundle list shows after gems are installed.

bundle list shows the gems installed in the current bundle with their versions. Since rack version 2.2.3 satisfies '~> 2.2', it will be listed.

🧠 Conceptual

intermediate

What does the Gemfile.lock file do?

In a Ruby project using Bundler, what is the main purpose of the Gemfile.lock file?

A It contains the source code of all gems used in the project.

B It records the exact versions of gems installed to ensure consistent installs.

C It specifies the Ruby version required by the project.

D It lists all available gems on RubyGems.org.

💡 Hint

Think about how Bundler ensures everyone uses the same gem versions.

Gemfile.lock locks the gem versions resolved during bundle install so that all developers and deployments use the exact same versions, avoiding conflicts.

🔧 Debug

advanced

Why does this Bundler install fail?

You run bundle install but get this error:
Bundler could not find compatible versions for gem "rails":
In Gemfile:
rails (~> 6.1.0)

Another dependency requires rails (~> 7.0)
What is the cause?

A The network connection to RubyGems.org is down.

B The Gemfile.lock is missing, so Bundler cannot install gems.

C The Gemfile requests rails 6.1.x but another dependency requires rails 7.0 or higher.

D The Ruby version is incompatible with rails 6.1.

💡 Hint

Look at the version requirements in the error message.

The error shows a version conflict: the Gemfile wants rails ~> 6.1.0 but another dependency requires rails ~> 7.0, so Bundler cannot resolve a compatible version.

📝 Syntax

advanced

Which Gemfile syntax is correct for specifying a source and a gem with a version constraint?

Choose the correct Gemfile syntax to specify RubyGems.org as the source and include the gem 'nokogiri' version '~> 1.12'.

A

source = 'https://rubygems.org'
gem 'nokogiri', version: '~> 1.12'

B

source: 'https://rubygems.org'
gem 'nokogiri' version '~> 1.12'

C

source('https://rubygems.org')
gem('nokogiri', '~> 1.12')

D

source 'https://rubygems.org'
gem 'nokogiri', '~> 1.12'

💡 Hint

Gemfile uses Ruby DSL syntax, not hash or method calls.

The correct syntax uses source 'url' and gem 'name', 'version' without colons or parentheses.

🚀 Application

expert

How to update a single gem without changing others?

You want to update only the 'puma' gem to the latest compatible version without updating other gems in your bundle. Which Bundler command should you use?

A bundle update puma

B bundle upgrade puma

C bundle install --update puma

D bundle install --only puma

💡 Hint

Check Bundler's command to update specific gems.

bundle update puma updates only the 'puma' gem and its dependencies, leaving other gems locked to their current versions.