One of my extensions has an API class where one of the parameters had "ApiBase::PARAM_RANGE_ENFORCE => false" among its values. This caused validation to fail, and I couldn't check in patches. I believe the issue is due to line 369 of tests/phpunit/structure/ApiStructureTest.php, the top line here:

				if ( isset( $config[ApiBase::PARAM_RANGE_ENFORCE] ) ) {
					$this->assertTrue(
						isset( $config[ApiBase::PARAM_MIN] ) ||
							isset( $config[ApiBase::PARAM_MAX] ),
						"$param: PARAM_RANGE_ENFORCE can only be set together with " .
							"PARAM_MIN or PARAM_MAX"
					);
				}

The code should be checking not just if the value is set, but if it's true.

By the way, I got rid of the line in my own extension, so this isn't an urgent issue for me.