# assertNan() >[info] ## assertNan(mixed $variable[, string $message = '']) 当 `$variable` 不是 `NAN` 时报告错误，错误讯息由 `$message` 指定。 **Example A.31. assertNan() 的用法** ~~~ <?php class NanTest extends PHPUnit_Framework_TestCase { public function testFailure() { $this->assertNan(1); } } ?> ~~~ ~~~ phpunit NanTest PHPUnit 5.0.0 by Sebastian Bergmann and contributors. F Time: 0 seconds, Memory: 5.00Mb There was 1 failure: 1) NanTest::testFailure Failed asserting that 1 is nan. /home/sb/NanTest.php:6 FAILURES! Tests: 1, Assertions: 1, Failures: 1. ~~~