Testing untestable codeStephan 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!

Not to freak out!

Testing untestable code

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

What is „untestable code“?

Testing untestable code

s

Testing untestable code

Wrong object construction

“new” is evil!

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

SUTSUTUnittestUnittest

In a perfect world...

Testing untestable code

SUTSUTUnittestUnittest

Legacy code is not perfect...

DependencyDependency

DependencyDependency

Testing untestable code

SUTSUTUnittestUnittest

Legacy code is not perfect...

DependencyDependency

DependencyDependency

...

...

Testing untestable code

SUTSUTUnittestUnittest

Legacy code is not perfect...

DependencyDependency

DependencyDependency

...

...

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);

}}

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

Testing untestable code

Object construction - Solution II

<?phpclass 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 environmemtvfsStream::setup('exampleDir');

// create directory in test enviromentmkdir(vfsStream::url('exampleDir').'/sample/');

// check if directory was createdecho 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?

What else?

Testing untestable code

Generative Programming

Testing untestable code

Generative Programming

ConfigurationConfiguration

Implementationcomponents

Implementationcomponents

Generatorapplication

Generatorapplication

ProductProductGeneratorGenerator

1 ... n

Testing untestable code

Generative Programming

ConfigurationConfiguration

Implementationcomponents

Implementationcomponents

Generatorapplication

Generatorapplication

GeneratorGenerator

ApplicationApplication

TestcasesTestcases

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 extendsSimpleFrameController {

public void execute(Frame frame, FeatureConfigconfig) {

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?

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