Ruby on Rails interview questions

Questions about automated tests in Ruby on Rails

Writing code for production without automated tests is a bad approach to web development, especially when we’re coding in Ruby, because the language itself requires web developers to write tests. Automated testing in Ruby on Rails helps reduce the burden on the QA team, and this greatly improves the workflow.

Automated testing is extremely important for startups. Here are the reasons.

All Ruby web developers should have a clear understanding of why to use automated tests, when to write them, and what types of tests exist. In addition to understanding test methods, every Ruby on Rails developer should know how to create a test case and should be familiar with testing guidelines and best practices. Here are some testing questions we can ask a Ruby on Rails developer:

  • What is unit testing (in the classical sense)?
  • What is the main test writing technique?
  • What are your favorite unit test writing tools?
  • What are your favorite feature test writing tools?

Ask a Ruby on Rails programmer about refactoring

Refactoring is an important step during the development of any application. Refactoring means that developers update the code they have already written to make it cleaner and more efficient. If the developer knows how to achieve a high level of performance, then in the future the team will be able to improve the application faster in accordance with changing customer requests. The following series of Ruby on Rails interview questions will help you evaluate a developer’s ability to write elegant code. Don’t forget that this question can be modified to focus on your own core development concerns:

  • What is code smell?
  • What are your favorite tools for finding code smells and potential bugs?
  • Why should you avoid bold controllers?
  • Why should you avoid fat models?
  • Explain methods for retrieving values, services, forms, views, queries, and policy objects.
  • Find out all the situations when it is better to refactor the code.

Submit a pair programming assignment

The next part of the Ruby on Rails interview always includes a test of the programmer’s skills paired with a senior web developer. We explain to the interlocutor that this is necessary to give free rein to his mind.

What is the purpose of the pair programming test? First of all, it allows us to look at the mindset of the developer. Once a Ruby on Rails programmer is given a task, they must come up with some methods or means to solve it. The pair programming challenge is very similar to a discussion, as our senior web developer helps the interviewee understand which solution might not only work, but be the best. Secondly, pair programming problems help us determine the developer’s ability to work in a team. The following is an example of tasks we can give during a Ruby on Rails interview.

Binary gap

A binary gap in a positive integer N is any maximum sequence of consecutive zeros that have surrounded ones at either end in the binary representation of N . For example, the number 9 has a binary representation of 1001 and contains a binary space of length 2. The number 529 has a binary representation of 1000010001 and contains two binary spaces, one of length 4 and one of length 3. The number 20 has a binary representation of 10100 and contains one binary space of length 1. Number 15 has a binary representation of 1111 and has no binary spaces.

Write a function def binary_gap(n) that, given a positive integer N , returns the length of the longest binary gap. The function should return 0 if N does not contain a binary space.

For example, if N = 1041 , the function should return 5 because N has a binary representation of 10000010001 and its longest binary space is 5.

Let’s pretend that:

  • N is an integer in the range [1..2 147 483 647].


  • expected worst-case time complexity is O(log(N)) ;
  • expected worst-case space complexity is O(1) .

Ruby on Rails developer homework

This is the last task that can be given to the interviewee. In order to find out if a Rails developer can use several technologies for web development. The interlocutor should be well versed in many front-end tools, including the JavaScript programming language, its frameworks and libraries. A good knowledge of the markup language and style sheets is definitely a must. We also include tasks to test a developer’s ability to write automated tests using tools such as RSpec, Capybara, and the like.

Homework may vary. For example, we can ask a Rails developer to implement a task with React, Ember, or Backbone instead of Angular. The specific task we give may depend on the specific project that the Rails developer would be working on if hired. This programming task, which should only be done by the applicant, is very valuable for testing his or her skills.

Technical Validation of Ruby on Rails Developer Skills with Online Tests

Online coding tests are probably the best way to determine the ability of Ruby on Rails developers to code. But it is important to choose the right one, since not all of them are the same.

Algorithmic tests are traditional, but they still fall short of expectations. They cannot really test a candidate’s knowledge of the environment. This is especially problematic for a Ruby on Rails developer. It’s not enough to know if someone can write an algorithm in Ruby, they should be able to use the Ruby on Rails environment when needed. There are a limited number of ways to solve algorithm problems. Also, plagiarism concerns mean you can’t use the usual resources that a developer would like from Google or Stack Overflow.

Probably the best way to test a developer’s Ruby on Rails programming skills is to give them a sample of their work. This includes giving the candidate the same task as on the first day of work. Then let the candidate complete the task in as natural a setting as possible. This means being able to use all the resources they would normally use. These include frameworks and libraries such as Rails and Sinatra, or other resources such as Stack Overflow and Google. Then you can evaluate the effectiveness of the solution they create in all cases, their business logic and the quality of the code.

Use these questions to interview the developer at your stage and make life easier for team leads 😉

Leave a Reply

Your email address will not be published. Required fields are marked *