Behaviour-Driven Development Kerry Buckley

Kerry Buckley

Evolution

Dirty Hacking

Automated Testing

Automated Testing class Adder def add a, b a + b end end class AdderTest < Test::Unit::TestCase def test_adder adder = Adder . new assert_equal 4 , adder.add( 2 , 2 ) assert_equal 2 , adder.add( 4 , - 2 ) end end

Are You Really Testing Your Code? class Adder def add a, b a + b end end class AdderTest < Test::Unit::TestCase def test_adder assert_equal 4 , 2 + 2 end end

Test-First Development

Test-First Development Failing tests Start Done Write code Write tests

Test-Driven Development

Test-Driven Development Failing test Clean code All tests pass Refactor

State-Based class DongleTest < Test::Unit::TestCase def test_wibble # Set up test inputs dongle = Dongle . new dongle.addString( &quot;foo&quot; ) dongle.addRemoteResource( &quot; http://foo.com/bar &quot; ) # Exercise functionality under test dongle.wibble! # Verify results are as expected dongle.answer.should == 42 end end

Bottom-Up

Behaviour-Driven Development

Behaviour-Driven Development Verification Specification State-based Interaction-based Bottom-up Outside-in Testing tool Design tool Invention Discovery

More Descriptive Test Names class AdderTest < Test::Unit::TestCase def test_should_add_two_positive_numbers assert_equal 4 , Adder . new .add( 2 , 2 ) end def test_should_add_a_positive_and_a_negative_number assert_equal 2 , Adder . new .add( 4 , - 2 ) end end

Matchers describe &quot;An adder&quot; do it &quot;should add two positive numbers&quot; do Adder . new .add( 2 , 2 ).should == 4 end it &quot;should add a positive and a negative number&quot; do Adder . new .add( 4 , - 2 ).should == 2 end end

Generated Documentation $ spec -f s adder_spec.rb An adder - should add two positive numbers - should add a positive and a negative number Finished in 0.005493 seconds 2 examples, 0 failures

More Matcher Examples @string .should == &quot;foo&quot; @array .should_not be_empty @hash .should have_key( :foo ) @object .should be_an_instance_of String lambda { @stack .pop }.should raise_error( StackUnderflowError )

Top-Down

Interaction-Based

Mock Objects Stand-ins for collaborating objects Mock the interface, not a specific object Verify that expected calls are made Not stubs! For your code only!

Stand-ins for collaborating objects

Mock the interface, not a specific object

Verify that expected calls are made

Not stubs!

For your code only!

Classicists v Mockists

Mock Objects Mock Mock

Boundary Objects

Integration Testing

Further Reading Introducing BDD (Dan North) http: //dannorth . net/introducing-bdd BDD Introduction http: //behaviour-driven .org/Introduction Mock Roles, Not Objects (Freeman, Mackinnon, Pryce, Walnes) http://www. jmock .org/oopsla2004. pdf BDD in Ruby (Dave Astels) http: //blog . daveastels . com/files/BDD_Intro . pdf