Add PdfMerger unit test.

tests/Unit/PdfMergerTest.php

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tomsgu\PdfMerger\Test\Unit;
+
+use PHPUnit\Framework\TestCase;
+use setasign\Fpdi\Fpdi;
+use Tomsgu\PdfMerger\Exception\InvalidArgumentException;
+use Tomsgu\PdfMerger\PdfCollection;
+use Tomsgu\PdfMerger\PdfMerger;
+
+/**
+ * @author Tomas Jakl <[email protected]>
+ */
+class PdfMergerTest extends TestCase
+{
+    const TEST_FILE = './tests/Data/landscape.pdf';
+
+    public function testEmptyCollection()
+    {
+        $collection = new PdfCollection();
+        $fpdi = new Fpdi();
+        $merger = new PdfMerger($fpdi);
+
+        $this->expectException(InvalidArgumentException::class);
+        $merger->merge($collection, 'new_file.pdf', PdfMerger::MODE_FILE);
+    }
+
+    public function testInvalidMode()
+    {
+        $collection = new PdfCollection();
+        $collection->addPdf(self::TEST_FILE);
+        $fpdi = new Fpdi();
+        $merger = new PdfMerger($fpdi);
+
+        $this->expectException(InvalidArgumentException::class);
+        $merger->merge($collection, 'new_file.pdf', 'ZZZ');
+    }
+}