public function testAddingSingularizationRules() {
		$before = Inflector::rules('singular');
		$result = Inflector::singularize('errata');
		$this->assertNull(Inflector::rules('singular', array('/rata/' => '\1ratus')));
		$this->assertEqual(Inflector::singularize('errata'), $result);

		Inflector::reset();
		$this->assertNotEqual(Inflector::singularize('errata'), $result);

		$after = Inflector::rules('singular');
		$expected = array(
			'rules', 'irregular', 'uninflected', 'regexUninflected', 'regexIrregular'
		);
		$this->assertEqual(array_keys($before), $expected);
		$this->assertEqual(array_keys($after), $expected);

		$result = array_diff($after['rules'], $before['rules']);
		$this->assertEqual($result, array('/rata/' => '\1ratus'));

		foreach (array('irregular', 'uninflected', 'regexUninflected', 'regexIrregular') as $key) {
			$this->assertIdentical($before[$key], $after[$key]);
		}

		$this->assertNull(Inflector::rules('singular', array('rules' => array(
			'/rata/' => '\1ratus'
		))));
		$this->assertIdentical(Inflector::rules('singular'), $after);
	}