Why testing is central to Ruby culture - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print a greeting message.

Ruby

puts [1]

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

Aecho "Hello, Ruby!"

BHello, Ruby!

Cprint "Hello, Ruby!"

D"Hello, Ruby!"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string.

Using print instead of puts.

In Ruby, puts prints the string to the screen. The string must be in quotes.

2fill in blank

medium

Complete the code to define a method that returns true if a number is even.

Ruby

def even_number?(num)
  num.[1]
end

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

Ais_even

Beven?

Codd?

Dcheck_even

Attempts:

3 left

💡 Hint

Common Mistakes

Using odd? instead of even?.

Trying to use non-existent methods like is_even.

The Ruby method even? returns true if the number is even.

3fill in blank

hard

Fix the error in the test code to check if 5 is odd using RSpec.

Ruby

RSpec.describe 'Number' do
  it 'checks if 5 is odd' do
    expect(5.[1]).to be true
  end
end

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

Ais_odd

Bcheck_odd

Codd?

Deven?

Attempts:

3 left

💡 Hint

Common Mistakes

Using even? which returns false for 5.

Using non-existent methods like is_odd.

In RSpec, to check if 5 is odd, use the Ruby method odd?.

4fill in blank

hard

Fill both blanks to create a hash of word lengths for words longer than 3 letters.

Ruby

lengths = {}
for word in words
  if word.[2] 3
    lengths[word] = word.[1]
  end
end

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

Alength

Bsize

Clength? >

Dlength >

Attempts:

3 left

💡 Hint

Common Mistakes

Using length? which is not a Ruby method.

Using incorrect comparison operators.

Use word.size to get the length of the word and compare it with 3 using >.

5fill in blank

hard

Fill all three blanks to create a hash of uppercase words and their lengths for words longer than 4 letters.

Ruby

result = {}
for word in words
  if word.length [3] 4
    result[[1]] = [2]
  end
end

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

Aword.upcase

Bword.length

C>

Dword.downcase

Attempts:

3 left

💡 Hint

Common Mistakes

Using word.downcase instead of uppercase.

Using wrong comparison operators.

Use word.upcase as the key, word.length as the value, and check if length is greater than 4 with >.

Practice

1. Why is testing considered central to Ruby culture?

easy

A. It is required by the Ruby language syntax.

B. It helps find mistakes early and ensures code works correctly.

C. It makes Ruby code run faster.

D. It replaces the need for writing code comments.

Solution

1. Step 1: Understand the purpose of testing in Ruby

   Testing is used to catch errors early and confirm that code behaves as expected.

2. Step 2: Compare options with Ruby culture

   Ruby culture emphasizes writing tests to build trust and maintain code quality, not speed or syntax rules.

3. Final Answer:

   It helps find mistakes early and ensures code works correctly. -> Option B

4. Quick Check:

   Testing = Early error detection [OK]

Hint: Testing finds bugs early and keeps code reliable [OK]

Common Mistakes:

• Thinking testing makes code faster
• Confusing testing with language syntax
• Believing tests replace comments

2. Which of the following is the correct way to start a simple test in Ruby using Minitest?

easy

A. class TestExample < Minitest::Test; def test_add; assert_equal 4, 2+2; end; end

B. def test_add; assert_equal 4, 2+2; end

C. test 'add' do; assert_equal 4, 2+2; end

D. class TestExample; def test_add; assert_equal 4, 2+2; end; end

Solution

1. Step 1: Identify correct Minitest class structure

   Minitest tests are defined inside a class inheriting from Minitest::Test.

2. Step 2: Check method and assertion syntax

   Test methods start with 'test_' and use assertions like assert_equal.

3. Final Answer:

   class TestExample < Minitest::Test; def test_add; assert_equal 4, 2+2; end; end -> Option A

4. Quick Check:

   Minitest class inherits Minitest::Test [OK]

Hint: Minitest tests inherit Minitest::Test class [OK]

Common Mistakes:

• Omitting inheritance from Minitest::Test
• Not prefixing test methods with 'test_'
• Using wrong test block syntax

3. What will be the output when running this Minitest code?

require 'minitest/autorun'

class TestMath < Minitest::Test
  def test_multiply
    assert_equal 15, 3 * 5
  end

  def test_fail
    assert_equal 10, 2 + 2
  end
end

medium

A. 1 test passed, 1 test failed

B. All tests passed

C. Syntax error

D. No tests run

Solution

1. Step 1: Analyze each test method

   test_multiply checks if 3*5 equals 15 (true), test_fail checks if 2+2 equals 10 (false).

2. Step 2: Determine test results

   One test passes, one test fails, so output shows 1 pass and 1 fail.

3. Final Answer:

   1 test passed, 1 test failed -> Option A

4. Quick Check:

   One true, one false test = 1 pass, 1 fail [OK]

Hint: Check each assertion result to find pass/fail count [OK]

Common Mistakes:

• Assuming all tests pass
• Expecting syntax error without error
• Thinking no tests run

4. Identify the error in this Ruby test code snippet:

require 'minitest/autorun'

class TestString < Minitest::Test
  def test_length
    assert_equal 5, 'hello'.length
  end

  def test_uppercase
    assert_equal 'HELLO', 'hello'.upcase
  end

  def test_fail
    assert_equal 4, 'test'.length
end

medium

A. Missing 'end' keyword for the class definition

B. Wrong inheritance from Minitest::Test

C. Missing 'end' keyword for the test_fail method

D. Incorrect assertion method used

Solution

1. Step 1: Count opening and closing blocks

   1 class + 3 defs opened (4 total), but only 3 'end' keywords; the last method 'test_fail' is missing its closing 'end'.

2. Step 2: Confirm methods have closings

   All other methods properly closed; error is missing 'end' for 'test_fail' method.

3. Final Answer:

   Missing 'end' keyword for the test_fail method -> Option C

4. Quick Check:

   Missing method 'end' causes syntax error [OK]

Hint: Count 'end' keywords to match methods and classes [OK]

Common Mistakes:

• Confusing missing method end with class end
• Thinking assertion method is wrong
• Assuming inheritance is incorrect

5. You want to ensure your Ruby code handles empty strings correctly. Which test best applies Ruby's testing culture to check this?

def reverse_string(str)
  str.reverse
end

hard

A. def test_reverse_empty
assert_equal nil, reverse_string('')
end

B. def test_reverse_empty
assert_equal false, reverse_string('')
end

C. def test_reverse_empty
assert_equal ' ', reverse_string('')
end

D. def test_reverse_empty
assert_equal '', reverse_string('')
end

Solution

1. Step 1: Understand function behavior with empty string

   Calling reverse on an empty string returns an empty string.

2. Step 2: Choose assertion matching expected output

   Test should expect '' (empty string), not nil, space, or false.

3. Final Answer:

   def test_reverse_empty assert_equal '', reverse_string('') end -> Option D

4. Quick Check:

   Empty string reversed is empty string [OK]

Hint: Test expected output exactly, empty string reverses to empty string [OK]

Common Mistakes:

• Expecting nil instead of empty string
• Using space or false as expected result
• Not testing edge cases like empty input