Writing Multiple Test Cases Together

In this lesson you will learn how to run several test cases together so you can verify a method efficiently. This is for anyone searching for "Ruby test cases how to write".

Testing one method against several input patterns at once is called unit testing. Preparing a spread of cases - normal values, boundary values, special values - helps you find bugs early.

The sample code collects several input/expected pairs in the array of hashes test_cases and compares add's result with the expectation one case at a time using each_with_index. Notice how passed counts the successes.

A common stumbling block for beginners is testing only the happy path and forgetting boundary values such as zero or negative numbers. Boundary-value testing is exactly the practice of deliberately checking those special situations.

In real development these tests run automatically every time the code changes, keeping quality steady. Adopting a dedicated framework such as RSpec takes this same idea considerably further.

📖 Reference code

def add(a, b)
  a + b
end

test_cases = [
  { a: 2, b: 3, expected: 5 },
  { a: -1, b: 1, expected: 0 },
  { a: 0, b: 0, expected: 0 },
]

passed = 0
test_cases.each_with_index do |tc, i|
  result = add(tc[:a], tc[:b])
  ok = result == tc[:expected]
  passed += 1 if ok
  puts "Test #{i + 1}: #{ok ? 'OK' : 'FAIL'}"
end
puts "#{passed}/#{test_cases.length} passed"

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Ruby directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).