Laravel artisan command testing assert exit code risky

I am running a basic artisan command test but phpunit complains that This test did not perform any assertions. But am asserting the exit code.

public function testCommandUsage()
{
   $this->artisan('cmd:test')->assertExitCode(0);
}

This test did not perform any assertions

OK, but incomplete, skipped, or risky tests!

Isn't assertExitCode and assertion?