Added a test class for the Database functions

tests/DatabaseTest.php

@@ -0,0 +1,53 @@
+<?php
+/**
+ * @file     DatabaseTest.php
+ * This class tests the functions in the Database class
+ * @package  PotatoORM
+ * @author   andrew <andrew.onyango@andela.com>
+ * @license  MIT => https://opensource.org/licenses/MIT
+ */
+
+namespace PotatoORM\Test;
+
+use PotatoORM\Database;
+use PotatoORM\Models\Person;
+use PHPUnit_Framework_TestCase;
+
+/**
+ *Tests for the Database class
+ *
+ * @category Test
+ * @package  PotatoORM
+ */
+class DatabaseTest extends PHPUnit_Framework_TestCase
+{
+    public function testCRUDMethods()
+    {
+        $db = new Database();
+        $id = -1;
+
+        $person = $this->getPerson(["john", "doe"]);
+        $id = $db->insert("Person", $person);
+        $this->assertFalse($id == -1);
+
+        $db->select("Person", " id = $id");
+        $person = $db->singleObject(get_called_class());
+        $this->assertEquals("john", $person->{"first_name"});
+
+        $person = $this->getPerson(["jane", "dizoe"]);
+        $db->update("Person", $person, " id = $id");
+        $db->select("Person", " id = $id");
+        $person = $db->singleObject(get_called_class());
+        $this->assertEquals("jane", $person->{"first_name"});
+
+        $db->delete("Person");
+    }
+
+    private function getPerson($array)
+    {
+        return [
+            "first_name" => $array[0],
+            "last_name"  => $array[1]
+        ];
+    }
+}