Added failing test of ITF14 checksum

tests/ChecksumBarcodeTest.php

@@ -0,0 +1,37 @@
+<?php
+
+use PHPUnit\Framework\TestCase;
+use Picqer\Barcode\Types\TypeEan13;
+use Picqer\Barcode\Types\TypeInterface;
+use Picqer\Barcode\Types\TypeITF14;
+
+class ChecksumBarcodeTest extends TestCase
+{
+    public static $supportedBarcodes = [
+        ['type' => TypeEan13::class, 'barcodes' => [
+            '081231723897' => '0812317238973',
+            '004900000463' => '0049000004632',
+        ]],
+        ['type' => TypeITF14::class, 'barcodes' => [
+            '0001234560001' => '00012345600012',
+            '0540014128876' => '05400141288766',
+        ]],
+    ];
+
+    public function testAllSupportedBarcodeTypes()
+    {
+        foreach ($this::$supportedBarcodes as $barcodeTestSet) {
+            $barcodeType = $this->getBarcodeType($barcodeTestSet['type']);
+
+            foreach ($barcodeTestSet['barcodes'] as $testBarcode => $expectedBarcode) {
+                $this->assertEquals($expectedBarcode, $barcodeType->getBarcodeData($testBarcode)->getBarcode());
+            }
+        }
+    }
+
+
+    private function getBarcodeType(string $typeClass): TypeInterface
+    {
+        return new $typeClass;
+    }
+}