Running the phpunit test suite from core as:
php test/phpunit/phpunit.php --testsuite extensions
Yields:
```
PHPUnit_Framework_Exception from line 144 of vendor/phpunit/phpunit/src/Framework/TestSuite.php:
Class "Structure" does not extend PHPUnit_Framework_TestCase.
Backtrace:
#0 vendor/phpunit/phpunit/src/Util/Configuration.php(898): PHPUnit_Framework_TestSuite->__construct(ReflectionClass)
#1 vendor/phpunit/phpunit/src/Util/Configuration.php(879): PHPUnit_Util_Configuration->getTestSuite(DOMElement, string)
#2 vendor/phpunit/phpunit/src/TextUI/Command.php(649): PHPUnit_Util_Configuration->getTestSuiteConfiguration(string)
#3 vendor/phpunit/phpunit/src/TextUI/Command.php(111): PHPUnit_TextUI_Command->handleArguments(array)
#4 vendor/phpunit/phpunit/src/TextUI/Command.php(100): PHPUnit_TextUI_Command->run(array, boolean)
#5 tests/phpunit/phpunit.php(134): PHPUnit_TextUI_Command::main()
#6 maintenance/doMaintenance.php(94): PHPUnitMaintClass->execute()
#7 tests/phpunit/phpunit.php(173): include(string)
#8 {main}
```
The reason is `tests/phpunit/suite.xml` defines a `structure` testsuite and PHPUnit attempts to load a class named `structure`, if such a class exists, it then asserts it is actuall a testcase class.
The problem is that WikiLexicalData defines a `Structure` class:
```
OmegaWiki/Attribute.php:60:class Structure {
```
And thus there is a clash. A good way to fix it would be to add namespace in WikiLexicalData.