Simple RSpec

_simple_rspec.rb

#!/usr/bin/env ruby
#encoding: UTF-8

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# Overly simplistic implementation of how a RSpec test works                   #
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def describe(object_under_test, &block)
  @obj_under_test = object_under_test
  @test_group     = block
end

def subject
  if @obj_under_test.is_a? Class
    @subject ||= @obj_under_test.new
  else
    @obj_under_test
  end
end

def before(&block) @before_hooks << block end
def after(&block)  @after_hooks  << block end

def it(description = nil, &block)
  @examples << Example.new(description, block)
end

Example = Struct.new(:description, :test) do
  attr_accessor :result
  def call
    @result = if test
                begin
                  test.call
                  :passed
                rescue => e
                  @failure = e
                  :failed
                end
              else
                :pending
              end
  end
end

# Setup some variables to keep track of hooks
@before_hooks = []
@after_hooks  = []
@examples     = []

# Allow a very simply TestUnit style assert for ease of testing
def assert(truthy)
  truthy or raise Error.new("Test failed.")
end


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# A simplistic view of how tests are run                                       #
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def run
  raise 'No object under test defined.' unless @obj_under_test

  puts @obj_under_test
  return unless @test_group

  # Find out what tests need to be run
  @test_group.call

  # Run the tests
  @examples.each_with_index do |example, index|
    @subject = nil
    puts "\n\nEXAMPLE #{index+1}:"
    begin
      @before_hooks.each(&:call)
      example.call
      puts "\n    #{example.description} => #{example.result.upcase}\n"
    rescue => e
      puts "\n    #{example.description} => failed\n"
    ensure
      @after_hooks.reverse_each(&:call)
    end
  end
end


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# Here's our sample RSpec example                                              #
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class Thing
  attr_reader :my_value
  def initialize
    @my_value = rand 5
  end
end

describe Thing do
  before { puts "BEFORE_BLOCK:: First before block" }
  after do
    print "AFTER_BLOCK:: should be called last!"
    print "    Reset @tmp_value(#{@tmp_value.inspect}) => "
    @tmp_value = nil
    puts "@tmp_value(#{@tmp_value.inspect})"
  end

  it 'has access to subject' do
    p subject
    assert subject.my_value < 5
  end

  it 'subject changes only between tests' do
    p subject
    assert subject.equal?(subject)
  end

  it "fails on error" do
    raise Error.new 'Sad face'
  end

  it 'works!' do
    assert @tmp_value == 'test'
  end

  before do
    @tmp_value = 'test'
    print "BEFORE_BLOCK:: Another before block"
    puts "     Set @tmp_value(#{@tmp_value.inspect})"
  end

  it 'is pending'

  after { puts "AFTER_BLOCK:: should be called first!!" }
end


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# Now we run the example
run

output.txt

# Output of the tests

Thing


EXAMPLE 1:
BEFORE_BLOCK:: First before block
BEFORE_BLOCK:: Another before block     Set @tmp_value("test")
#<Thing:0x007fcd110a26a8 @my_value=3>

    has access to subject => PASSED

AFTER_BLOCK:: should be called first!!
AFTER_BLOCK:: should be called last!    Reset @tmp_value("test") => @tmp_value(nil)


EXAMPLE 2:
BEFORE_BLOCK:: First before block
BEFORE_BLOCK:: Another before block     Set @tmp_value("test")
#<Thing:0x007fcd110a2220 @my_value=4>

    subject changes only between tests => PASSED

AFTER_BLOCK:: should be called first!!
AFTER_BLOCK:: should be called last!    Reset @tmp_value("test") => @tmp_value(nil)


EXAMPLE 3:
BEFORE_BLOCK:: First before block
BEFORE_BLOCK:: Another before block     Set @tmp_value("test")

    fails on error => FAILED

AFTER_BLOCK:: should be called first!!
AFTER_BLOCK:: should be called last!    Reset @tmp_value("test") => @tmp_value(nil)


EXAMPLE 4:
BEFORE_BLOCK:: First before block
BEFORE_BLOCK:: Another before block     Set @tmp_value("test")

    works! => PASSED

AFTER_BLOCK:: should be called first!!
AFTER_BLOCK:: should be called last!    Reset @tmp_value("test") => @tmp_value(nil)


EXAMPLE 5:
BEFORE_BLOCK:: First before block
BEFORE_BLOCK:: Another before block     Set @tmp_value("test")

    is pending => PENDING

AFTER_BLOCK:: should be called first!!
AFTER_BLOCK:: should be called last!    Reset @tmp_value("test") => @tmp_value(nil)