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Testing untestable code - STPCon11
 

Testing untestable code - STPCon11

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    Testing untestable code - STPCon11 Testing untestable code - STPCon11 Presentation Transcript

    • Testing untestable code Stephan Hochdörfer, bitExpert AG
    • Testing untestable code About me  Stephan Hochdörfer, bitExpert AG  Department Manager Research Labs  S.Hochdoerfer@bitExpert.de  @shochdoerfer
    • Testing untestable code No excuse for writing bad code!
    • Testing untestable code Not to freak out!
    • Testing untestable code Creativity matters!
    • Testing untestable code "There is no secret to writing tests, there are only secrets to write testable code!" Miško Hevery
    • Testing untestable code What is „untestable code“?
    • Testing untestable code Wrong object construction “new” is evil! s
    • Testing untestable code Tight coupling
    • Testing untestable code Uncertainty
    • Testing untestable code "...our test strategy requires us to have more control [...] of the sut." Gerard Meszaros, xUnit Test Patterns: Refactoring Test Code
    • Testing untestable code In a perfect world... Unittest Unittest SUT SUT
    • Testing untestable code Legacy code is not perfect... Dependency Dependency Unittest Unittest SUT SUT Dependency Dependency
    • Testing untestable code ... Legacy code is not perfect... Dependency Dependency Unittest Unittest SUT SUT Dependency Dependency ...
    • Testing untestable code ... Legacy code is not perfect... Dependency Dependency Unittest Unittest SUT SUT Dependency Dependency ...
    • Testing untestable code How to get „testable“ code?
    • Testing untestable code How to get „testable“ code? Refactoring
    • Testing untestable code "Before you start refactoring, check that you have a solid suite of tests." Martin Fowler, Refactoring
    • Testing untestable code Hope? - Nope...
    • Testing untestable code Which path to take?
    • Testing untestable code Which path to take? Do not change existing code!
    • Testing untestable code Examples Object construction External resources Language issues
    • Testing untestable code Object construction public class Car { private Engine engine; public Car(String engine) { this.engine = EngineFactory.getByType(engine); } }
    • Testing untestable code Object construction - Solution public class MyLoader extends ClassLoader { protected Class findClass(String name) throws ClassNotFoundException { try { String path = name.replace(., /); // @TODO: change path and read file, // @TODO: define package // @TODO: define class } catch(Exception e){ throw new ClassNotFoundException(name); } } }
    • Testing untestable code Object construction - Solution II <?php class MyStreamWrapper { private $_handler; function stream_open($path, $mode, $options, &$opened_path) { stream_wrapper_restore(file); // @TODO: modify $path before fopen $this->_handler = fopen($path, $mode); stream_wrapper_unregister(file); stream_wrapper_register(file, MyStreamWrapper); return true; } }
    • Testing untestable code External resources
    • Testing untestable code External resources Database Webservice Filesystem Mailserver
    • Testing untestable code External resources – Mock database
    • Testing untestable code External resources – Mock database Provide own db driver
    • Testing untestable code External resources – Mock database junit + dbunit
    • Testing untestable code External resources – Mock database Proxy for your SQL Server
    • Testing untestable code External resources – Mock webservice
    • Testing untestable code External resources – Mock webservice Provide own implementation
    • Testing untestable code External resources – Mock webservice Do not forget! Url redirection via /etc/hosts
    • Testing untestable code External resources – Mock filesystem
    • Testing untestable code External resources – Mock filesystem Commons-VFS vfsStream
    • Testing untestable code External resources – Mock filesystem <?php // set up test environmemt vfsStream::setup(exampleDir); // create directory in test enviroment mkdir(vfsStream::url(exampleDir)./sample/); // check if directory was created echo vfsStreamWrapper::getRoot()->hasChild(sample);
    • Testing untestable code External resources – Mock Mailserver
    • Testing untestable code External resources – Mock Mailserver Use fake mail server
    • Testing untestable code Dealing with language issues
    • Testing untestable code Dealing with language issues Testing your privates?
    • Testing untestable code Dealing with language issues final Method methods[] = o.getClass().getDeclaredMethods(); for (int i = 0; i < methods.length; ++i) { if (methodName.equals(methods[i].getName())) { try { methods[i].setAccessible(true); return methods[i].invoke(o, params); } catch (IllegalAccessException ex) { } catch (InvocationTargetException ite) { } } return null; }
    • Testing untestable code Dealing with language issues Overwrite internal functions?
    • Testing untestable code What else?
    • Testing untestable code What else? Generative Programming
    • Testing untestable code Generative Programming Configuration Configuration 1 ... n Implementation Implementation Generator Generator Product components components Product Generator Generator application application
    • Testing untestable code Generative Programming Configuration Configuration Application Application Implementation Implementation Generator Generator components components Testcases Testcases Generator Generator application application
    • Testing untestable code Generative Programming A frame is a data structure for representing knowledge.
    • Testing untestable code A Frame instance public class Car { private Engine engine; public Car(String engine) { this.engine = <!{Factory}!>.getByType(engine); } }
    • Testing untestable code The Frame controller public class MyFrameController extends SimpleFrameController { public void execute(Frame frame, FeatureConfig config) { if(config.hasFeature("unittest")) { frame.setSlot("Factory", "FactoryMock"); } else { frame.setSlot("Factory", "EngineFactory"); } } }
    • Testing untestable code Generated result - Testcase public class Car { private Engine engine; public Car(String engine) { this.engine = FactoryMock.getByType(engine); } }
    • Testing untestable code Generated result - Application public class Car { private Engine engine; public Car(String engine) { this.engine = EngineFactory.getByType(engine); } }
    • Testing untestable code What is possible?
    • Testing untestable code What is possible? Show / hide parts of the code
    • Testing untestable code What is possible? Change content of global vars!
    • Testing untestable code What is possible? Define pre- or postfixes!
    • Testing untestable code Is it worth it?
    • Thank you for attending this session. Please fill out an evaluation form.