Create custom namespace in phpunit test for MediaWiki extension

Question

In phpunit tests for a MediaWiki extension, I am having trouble creating a custom namespace:

class NameSpaceTestCase extends \MediaWikiTestCase {
  public function testCustomNameSpace() {
    $ns = 4000;
    $this->setMwGlobals( [
      "wgExtraNamespaces[$ns]" => 'custom_namespace'
    ] );
    // global $wgExtraNamespaces;
    // $wgExtraNamespaces[$ns] = 'custom_namespace';
    $this->insertPage( 'in custom namespace', 'This is a page in a custom namespace', $ns );
    $this->assertTrue( MWNamespace::exists( $ns ), "The name space with id $ns should exist!" );
  }
}

The assertion that the namespace exists (in the last line of code) fails.

When I uncomment the currently commented lines (and comment the call to setMwGlobals instead) it still fails.

How can I programmatically create a namespace in MediaWiki?

Answer 1

setMwGlobals is not really useful for changing parts of globals; you can use mergeMwGlobalArrayValue instead, or use stashMwGlobals to make the test automatically restore the old value, then change it by hand. Plus you must make sure the old value is not stored anywhere - namespaces are looked up early in the request initialization lifecycle, and they include various things that are not that cheap (like running hooks for getting dynamically defined namespaces, and fetching translations) so tend to be cached. Unfortunately there isn't really any way to check that short of trying and the looking through the call tree and seeing where the value comes from. (MediaWiki is slowly moving towards a dependency injection based architecture where tests have more control over the state of the application, but is not quite there yet.)

Specifically, you can do something like

class NameSpaceTestCase extends \MediaWikiTestCase {
  public function testCustomNameSpace() {
    global $wgContLang;
    $ns = 4000;
    $this->mergeMwGlobalArrayValue( 'wgExtraNamespaces', [
      $ns => 'custom_namespace',
    ] );
    MWNamespace::getCanonicalNamespaces( true ); // break namespace cache
    $wgContLang->resetNamespaces(); // break namespace localization cache
    $this->insertPage( 'in custom namespace', 'This is a page in a custom namespace', $ns );
    $this->assertTrue( MWNamespace::exists( $ns ), "The name space with id $ns should exist!" );
  }
}