private function _checkUnusedPrivateFunctions() {
		if ($this->_isActive('checkUnusedPrivateFunctions')) {

			// We make a diff between the list of declared private functions and the list of called functions.
			// This is a very approximative test, we don't test that the called function is from the good class.
			// The usedFunctions array contains a lot of false positives
			$uncalledFunctions = array_diff($this->_privateFunctions, $this->_usedFunctions);

			foreach ($uncalledFunctions as $uncalledFunction) {

				$msg = $this->_getMessage('UNUSED_PRIVATE_FUNCTION', $uncalledFunction);
				// Direct call to reporter to include a custom line number.
				$this->_writeError('checkUnusedPrivateFunctions', $msg, $this->_privateFunctionsStartLines[$uncalledFunction], $this->_config->getTestLevel('checkUnusedPrivateFunctions'));
			}
		}
	}