Add test for excel document content

src/TestsExcelDocuments.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Zoomyboy\TableDocument;
+
+use PhpOffice\PhpSpreadsheet\Writer\Csv;
+use PHPUnit\Framework\Assert;
+
+trait TestsExcelDocuments
+{
+
+    public function assertExcelContent(string $should, string $content): void
+    {
+        $filename = sys_get_temp_dir() . '/' . str()->uuid()->toString();
+        file_put_contents($filename, $content);
+        $spreadsheet = \PhpOffice\PhpSpreadsheet\IOFactory::load($filename);
+        $writer = new Csv($spreadsheet);
+        $writer->save($filename);
+        $spreadsheet->disconnectWorksheets();
+        $contents = file_get_contents($filename);
+        unlink($filename);
+        Assert::assertStringContainsString($should, $contents);
+    }
+}