RSpec expectations and matchers in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of expect() in RSpec?

expect() is used to define an expectation in RSpec. It wraps the actual value you want to test, so you can check if it meets certain conditions using matchers.

beginner

What does the matcher eq check for in RSpec?

The eq matcher checks if the actual value is equal to the expected value using Ruby's == operator.

intermediate

How do you test if a method raises an error using RSpec?

You use expect { ... }.to raise_error(ErrorClass). The block contains the code that should raise the error, and raise_error matcher checks for it.

intermediate

What is the difference between eq and eql matchers?

eq checks for value equality (==), while eql checks for both value and type equality (eql? method).

beginner

How can you check if an array includes a specific element in RSpec?

Use expect(array).to include(element). The include matcher tests if the element is present in the array.

Which RSpec matcher checks if two values are exactly the same object?

A eq

B eql

C equal

D include

The equal matcher checks if two values are the same object (identity), unlike eq or eql which check value equality.

How do you write an expectation that a method call changes a value by 1?

A expect(value).to change.by(1)

B expect(method_call).to eq(1)

C expect { method_call }.to raise_error(1)

D expect { method_call }.to change { value }.by(1)

The change matcher is used with a block to check if a value changes by a certain amount after running code.

What does expect(value).not_to eq(5) mean?

A Value should not be equal to 5

B Value should be equal to 5

C Value should raise an error 5 times

D Value should include 5

The not_to negates the expectation, so it expects the value to NOT be equal to 5.

Which matcher would you use to check if a string matches a pattern?

A match

B include

C eq

D raise_error

The match matcher checks if a string matches a regular expression pattern.

How do you test if a block of code raises any error in RSpec?

A expect(code).to raise_error

B expect { code }.to raise_error

C expect { code }.to eq(error)

D expect(code).to eq(error)

Use expect { ... }.to raise_error with a block to test if any error is raised.

Explain how to use RSpec expectations and matchers to test if a method returns the expected value.

Think about wrapping the method call with expect and using a matcher to compare.

Describe how to test error handling in RSpec using expectations and matchers.

Remember that error testing uses a block inside expect.