TeamTNT\TNTSearch\Indexer\TNTIndexer::buildTrigrams PHP Method

    public function buildTrigrams($keyword)
    {
        $t = "__" . $keyword . "__";
        $trigrams = "";
        for ($i = 0; $i < strlen($t) - 2; $i++) {
            $trigrams .= substr($t, $i, 3) . " ";
        }
        return trim($trigrams);
    }

 public function testBuildTrigrams()
 {
     $indexer = new TNTIndexer();
     $trigrams = $indexer->buildTrigrams('created');
     $this->assertEquals('__c _cr cre rea eat ate ted ed_ d__', $trigrams);
     $trigrams = $indexer->buildTrigrams('mood');
     $this->assertEquals('__m _mo moo ood od_ d__', $trigrams);
     $trigrams = $indexer->buildTrigrams('death');
     $this->assertEquals('__d _de dea eat ath th_ h__', $trigrams);
     $trigrams = $indexer->buildTrigrams('behind');
     $this->assertEquals('__b _be beh ehi hin ind nd_ d__', $trigrams);
     $trigrams = $indexer->buildTrigrams('usually');
     $this->assertEquals('__u _us usu sua ual all lly ly_ y__', $trigrams);
     $trigrams = $indexer->buildTrigrams('created');
     $this->assertEquals('__c _cr cre rea eat ate ted ed_ d__', $trigrams);
 }