Ruby on Rails Quality Control & Assurance 5

Question 1

Which approach correctly stubs an instance method on a specific object in RSpec without affecting other instances?

Accepted Answer

allow(instance).to receive(:method_name).and_return(value)

Answer

`allow(obj).to receive` sets up a message expectation on that specific instance only, leaving other instances of the class unaffected.

Question 2

In Rails, what does `assert_difference('Model.count', 2)` verify in a test block?

Accepted Answer

That exactly 2 new records were added to the database during the block's execution

Answer

`assert_difference` evaluates the expression before and after the block and asserts the difference equals the given delta (default 1, here 2).

Question 3

What is the purpose of parallel test execution in Rails via `parallelize(workers: :number_of_processors)`?

Accepted Answer

Split the test suite across multiple processes to reduce total wall-clock run time

Answer

Rails' `parallelize` forks the test suite into N worker processes each with its own test database, dramatically reducing total test time on multi-core machines.

Question 4

Which security linting concern would Brakeman flag in a Rails view that renders `<%= params[:name] %>`?

Accepted Answer

Cross-site scripting (XSS) via unfiltered user input

Answer

Even though Rails auto-escapes ERB output, Brakeman flags direct `params` rendering as a potential XSS vector because the data originates from untrusted user input.

Question 5

In RSpec, what is the difference between `before(:each)` and `before(:all)` hooks?

Accepted Answer

`before(:each)` runs before every example; `before(:all)` runs once before all examples in the group and shares state

Answer

`before(:all)` (also `:context`) runs the block once, with shared mutable state potentially causing order-dependent failures between examples.

Ruby on Rails Practice Test

Ruby on Rails Practice Test

Ruby on Rails Quality Control & Assurance 5