RSpec expectations and matchers in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the variable result equals 10 using RSpec.

Ruby

expect(result).to [1] 10

Drag options to blanks, or click blank then click option'

Abe

Beq

Chave

Dinclude

Attempts:

3 left

💡 Hint

Common Mistakes

Using be which checks object identity, not value equality.

Using have or include which are for collections.

The eq matcher checks if the value is equal to the expected value.

2fill in blank

medium

Complete the code to check if the array numbers includes the number 5.

Ruby

expect(numbers).to [1] 5

Drag options to blanks, or click blank then click option'

Ainclude

Bcontain

Cmatch

Deq

Attempts:

3 left

💡 Hint

Common Mistakes

Using eq which checks for exact equality, not inclusion.

Using contain which is not a valid RSpec matcher.

The include matcher checks if a collection contains a specific element.

3fill in blank

hard

Fix the error in the code to check if the string message starts with 'Hello'.

Ruby

expect(message).to [1]('Hello')

Drag options to blanks, or click blank then click option'

Aeq

Binclude

Cmatch

Dstart_with

Attempts:

3 left

💡 Hint

Common Mistakes

Using eq which checks full equality.

Using include which checks for substring anywhere.

Using match which expects a regex.

The start_with matcher checks if a string begins with the given substring.

4fill in blank

hard

Fill both blanks to check if the variable value is greater than 5 and less than 10.

Ruby

expect(value).to be [1] 5.and be [2] 10

Drag options to blanks, or click blank then click option'

A>

B<

C==

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using equality operators instead of comparison.

Reversing the comparison signs.

The be > matcher checks if the value is greater than 5, and be < checks if it is less than 10.

5fill in blank

hard

Fill all three blanks to check if the hash user has a key :name with value 'Alice' and the key :age is greater than 20.

Ruby

expect(user). [1] include([2] => 'Alice'}) and expect(user[:age]).to be [3] 20

Drag options to blanks, or click blank then click option'

Ato

B:name

C>

Dhave_key

Attempts:

3 left

💡 Hint

Common Mistakes

Using have_key instead of include for key-value pairs.

Using wrong comparison operators for age.

Use to with include to check the key-value pair, and be > to check the age.

Practice

1. What does the RSpec matcher expect(value).to eq(5) check for?

easy

A. It checks if value is less than 5.

B. It checks if value is greater than 5.

C. It checks if value is not equal to 5.

D. It checks if value is equal to 5.

Solution

1. Step 1: Understand the eq matcher

   The eq matcher tests for equality between the expected and actual values.

2. Step 2: Analyze the expectation

   expect(value).to eq(5) means the test expects value to be exactly 5.

3. Final Answer:

   It checks if value is equal to 5. -> Option D

4. Quick Check:

   eq matcher = equality check [OK]

Hint: Remember eq means exact equality check [OK]

Common Mistakes:

• Confusing eq with greater_than or less_than
• Thinking eq checks for inequality
• Mixing up expect().to and expect().not_to

2. Which of the following is the correct syntax to check that an array includes the number 3 in RSpec?

easy

A. expect(array).to has(3)

B. expect(array).to include(3)

C. expect(array).to contains(3)

D. expect(array).to has_key(3)

Solution

1. Step 1: Identify the correct matcher for inclusion

   The include matcher checks if a collection contains a specific element.

2. Step 2: Match syntax with RSpec standards

   expect(array).to include(3) is the correct syntax to check if 3 is in the array.

3. Final Answer:

   expect(array).to include(3) -> Option B

4. Quick Check:

   include matcher = check element presence [OK]

Hint: Use include to check if collection has an element [OK]

Common Mistakes:

• Using has or contains which are not valid RSpec matchers
• Using has_key which is for hashes, not arrays
• Forgetting to use expect().to syntax

3. What will be the output of this RSpec test snippet?

describe 'Number test' do
  it 'checks if number is odd' do
    number = 7
    expect(number.odd?).to be true
  end
end

medium

A. The test passes because 7 is odd.

B. The test fails because 7 is not odd.

C. SyntaxError due to incorrect matcher usage.

D. The test passes but warns about deprecated syntax.

Solution

1. Step 1: Understand the code logic

   The variable number is set to 7, which is an odd number.

2. Step 2: Analyze the expectation

   expect(number.odd?).to be true checks if number.odd? returns true, which it does for 7.

3. Final Answer:

   The test passes because 7 is odd. -> Option A

4. Quick Check:

   odd? returns true for odd numbers [OK]

Hint: odd? returns true for odd numbers, expect that [OK]

Common Mistakes:

• Assuming 7 is even
• Confusing be true with eq true
• Thinking syntax is wrong here

4. Identify the error in this RSpec expectation:

expect(user.name).to eq nil

medium

A. Should use not_to eq nil to check for nil.

B. Missing parentheses around eq(nil).

C. Should use be_nil matcher instead of eq nil.

D. No error; the syntax is correct.

Solution

1. Step 1: Understand nil checking in RSpec

   While eq nil works, the preferred matcher for nil is be_nil for clarity and style.

2. Step 2: Identify best practice

   Using expect(user.name).to be_nil is clearer and idiomatic in RSpec.

3. Final Answer:

   Should use be_nil matcher instead of eq nil. -> Option C

4. Quick Check:

   Use be_nil for nil checks [OK]

Hint: Use be_nil matcher for nil checks, not eq nil [OK]

Common Mistakes:

• Thinking eq nil is a syntax error
• Adding unnecessary parentheses
• Using not_to eq nil to check for nil

5. You want to test that a method calculate returns a value greater than 10 but less than 20. Which RSpec expectation correctly checks this?

hard

A. expect(calculate).to satisfy { |v| v > 10 && v < 20 }

B. expect(calculate).to be > 10 and be < 20

C. expect(calculate).to be_between(10, 20).exclusive

D. expect(calculate).to be_between(11, 19).inclusive

Solution

1. Step 1: Understand the range requirement

   The value must be greater than 10 and less than 20, excluding 10 and 20 themselves.

2. Step 2: Analyze each option

   expect(calculate).to be > 10 and be < 20: expect(calculate).to be > 10 and be < 20 is invalid syntax; correct chaining uses (be > 10).and(be < 20).
   Options C and D: be_between is not a built-in RSpec matcher.
   expect(calculate).to satisfy { |v| v > 10 && v < 20 }: expect(calculate).to satisfy { |v| v > 10 && v < 20 } correctly checks the condition using a standard flexible matcher.

3. Step 3: Choose the best matcher

   expect(calculate).to satisfy { |v| v > 10 && v < 20 } is the correct and explicit choice using standard RSpec.

4. Final Answer:

   expect(calculate).to satisfy { |v| v > 10 && v < 20 } -> Option A

5. Quick Check:

   satisfy matcher = custom condition check [OK]

Hint: Use satisfy with block for complex conditions [OK]

Common Mistakes:

• Using non-standard be_between matcher
• Trying to chain matchers with 'and' incorrectly
• Ignoring boundary conditions in range checks