Test::Unit Ruby Skill

Core Patterns

Basic Test

require 'test/unit'

class TestCalculator < Test::Unit::TestCase
  def setup
    @calc = Calculator.new
  end

  def test_addition
    assert_equal(5, @calc.add(2, 3), "2 + 3 should equal 5")
  end

  def test_subtraction
    assert_equal(1, @calc.subtract(3, 2))
  end

  def test_division_by_zero
    assert_raise(ZeroDivisionError) { @calc.divide(10, 0) }
  end

  def test_float_division
    assert_in_delta(3.33, @calc.divide(10, 3), 0.01)
  end

  def teardown
    # cleanup
  end
end

Assertions

assert_equal(expected, actual, message = nil)
assert_not_equal(unexpected, actual)
assert_true(value)
assert_false(value)
assert_nil(value)
assert_not_nil(value)
assert_instance_of(klass, obj)
assert_kind_of(klass, obj)
assert_respond_to(obj, :method_name)
assert_match(/pattern/, string)
assert_no_match(/pattern/, string)
assert_include(collection, item)
assert_not_include(collection, item)
assert_empty(collection)
assert_not_empty(collection)
assert_raise(ErrorClass) { block }
assert_nothing_raised { block }
assert_in_delta(expected, actual, delta)
assert_operator(value, :>, 5)
assert_send([obj, :method, arg])
assert_block("message") { condition }

Test Fixtures

class TestDatabase < Test::Unit::TestCase
  def self.startup
    # Once before all tests in class
    @@db = Database.connect('test')
  end

  def self.shutdown
    # Once after all tests in class
    @@db.disconnect
  end

  def setup
    # Before each test
    @@db.begin_transaction
  end

  def teardown
    # After each test
    @@db.rollback
  end
end

Test Ordering and Naming

class TestUserService < Test::Unit::TestCase
  # Methods must start with 'test_'
  def test_create_user
    user = UserService.create('Alice', 'alice@test.com')
    assert_not_nil(user)
    assert_equal('Alice', user.name)
  end

  def test_find_user_by_email
    user = UserService.find_by_email('alice@test.com')
    assert_instance_of(User, user)
  end
end

Setup: gem install test-unit

Run: ruby test/test_calculator.rb or ruby -Itest -e "Dir.glob('test/**/test_*.rb').each{|f| require f}"

Autodiscovery: testrb test/ (with test-unit gem)

Deep Patterns

For advanced patterns, debugging guides, CI/CD integration, and best practices, see reference/playbook.md.