0.0

require_relative '0_parent_child'
require 'rspec'

describe ParentClass do

  it 'creates a child class' do
    expect(described_class.new.create_child_class).to be_a(ChildClass)
  end

end

describe ChildClass do

  it 'does something' do
    expect(described_class.new.do_something).to eq(42 * 80)
  end

end

0.1

class ParentClass
  def create_child_class
    childClass = ChildClass.new
  end
end

class ChildClass
  def do_something
    42 * 80
  end
end

0.2

~/P/R/test_example ❯❯❯ rspec 0_parent_child_spec.rb                                                                           
..

Finished in 0.00136 seconds (files took 0.08179 seconds to load)
2 examples, 0 failures

1.0

require_relative '1_parent_child'
require 'rspec'

describe ParentClass do

  it 'creates a child class' do
    expect(described_class.new.create_child_class).to be_a(ChildClass)
  end

end

describe ChildClass do

  it 'does something' do
    expect(described_class.new(42).do_something).to eq(42 * 80)
  end

end

1.1

~/P/R/test_example ❯❯❯ rspec 1_parent_child_spec.rb                                                                           
.F

Failures:

  1) ChildClass does something
     Failure/Error: expect(described_class.new(42).do_something).to eq(42 * 80)
     ArgumentError:
       wrong number of arguments (1 for 0)
     # ./1_parent_child_spec.rb:15:in `initialize'
     # ./1_parent_child_spec.rb:15:in `new'
     # ./1_parent_child_spec.rb:15:in `block (2 levels) in <top (required)>'

Finished in 0.00075 seconds (files took 0.08221 seconds to load)
2 examples, 1 failure

Failed examples:

rspec ./1_parent_child_spec.rb:14 # ChildClass does something

1.2

class ParentClass
  def create_child_class
    childClass = ChildClass.new
  end
end

class ChildClass

  def initialize(some_parameter)
  end

  def do_something
    42 * 80
  end
end

1.3

~/P/R/test_example ❯❯❯ rspec 1_parent_child_spec.rb                                                                           
F.

Failures:

  1) ParentClass creates a child class
     Failure/Error: expect(described_class.new.create_child_class).to be_a(ChildClass)
     ArgumentError:
       wrong number of arguments (0 for 1)
     # ./1_parent_child.rb:9:in `initialize'
     # ./1_parent_child.rb:3:in `new'
     # ./1_parent_child.rb:3:in `create_child_class'
     # ./1_parent_child_spec.rb:7:in `block (2 levels) in <top (required)>'

Finished in 0.00088 seconds (files took 0.10206 seconds to load)
2 examples, 1 failure

Failed examples:

rspec ./1_parent_child_spec.rb:6 # ParentClass creates a child class

1.4

class ParentClass
  def create_child_class
    childClass = ChildClass.new(nil)
  end
end

class ChildClass

  def initialize(some_parameter)
  end

  def do_something
    42 * 80
  end
end

1.5

~/P/R/test_example ❯❯❯ rspec 1_parent_child_spec.rb                                                                           
..

Finished in 0.00102 seconds (files took 0.08399 seconds to load)
2 examples, 0 failures

2.0

require_relative '1_parent_child'
require 'rspec'

describe ParentClass do

  it 'creates a child class' do
    expect(described_class.new.create_child_class).to be_a(ChildClass)
  end

end

describe ChildClass do

  it 'does something' do
    expect(described_class.new(37).do_something).to eq(37 * 80)
  end

end

2.1

~/P/R/test_example ❯❯❯ rspec 1_parent_child_spec.rb
.F

Failures:

  1) ChildClass does something
     Failure/Error: expect(described_class.new(37).do_something).to eq(37 * 80)

       expected: 2960
            got: 3360

       (compared using ==)
     # ./1_parent_child_spec.rb:15:in `block (2 levels) in <top (required)>'

Finished in 0.00109 seconds (files took 0.08437 seconds to load)
2 examples, 1 failure

Failed examples:

rspec ./1_parent_child_spec.rb:14 # ChildClass does something