Build/Test Tools: Add assertNotFalse() method to WP_UnitTestCase and use it where appropriate.

Props peterwilsoncc.
Fixes #39219.

git-svn-id: https://develop.svn.wordpress.org/trunk@39919 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/includes/testcase.php

@@ -456,6 +456,18 @@ class WP_UnitTestCase extends PHPUnit_Framework_TestCase {
 		}
 	}
 
+	/**
+	 * Asserts that a condition is not false.
+	 *
+	 * @param bool   $condition
+	 * @param string $message
+	 *
+	 * @throws PHPUnit_Framework_AssertionFailedError
+	 */
+	public static function assertNotFalse( $condition, $message = '' ) {
+		self::assertThat( $condition, self::logicalNot( self::isFalse() ), $message );
+	}
+
 	/**
 	 * Modify WordPress's query internals as if a given URL has been requested.
 	 *