Some text.

' .
            'Valid link

';
        $paddedurl = str_pad($originalurl, 6000, 'z');
        $validpaddedurl = '
Some text.


';
        $validpaddedurl = str_pad($validpaddedurl, 6000 + (strlen($validpaddedurl) - strlen($originalurl)), 'z');

        $invalidtexts = array(
            'href="http://moodle.org/testfile/test.mp3"',
            'test test',
            'test test',
            'test test',
            'test test',
            'sample',
            '',
            'test',
            'test mp3',
            '',
            'test',
            'test',
            'test mp3',
            'test mp3',
            'test mp3',
            // Test a long URL over 4096 characters.
            $longurl
        );

        //test for invalid link
        foreach ($invalidtexts as $text) {
            $msg = "Testing text: ". $text;
            $filter = $filterplugin->filter($text);
            $this->assertEquals($text, $filter, $msg);
        }

        // Valid mediaurl followed by a longurl.
        $precededlongurl = 'test.mp3'. $longurl;
        $filter = $filterplugin->filter($precededlongurl);
        $this->assertEquals(1, substr_count($filter, ''));
        $this->assertStringContainsString($longurl, $filter);

        // Testing for cases where: to be filtered content has 6+ text afterwards.
        $filter = $filterplugin->filter($paddedurl);
        $this->assertEquals($validpaddedurl, $filter, $msg);
    }
}