Added mongo test trait.

Allows mongounit to be used with mixed database test cases (ie, it
can't extend the mongounit testcase). 5.4+ only.

src/Zumba/PHPUnit/Extensions/Mongo/TestTrait.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Zumba\PHPUnit\Extensions\Mongo;
+use \Zumba\PHPUnit\Extensions\Mongo\DataSet\DataSet;
+
+trait TestTrait {
+
+	/**
+	 * Setup the mongo db with fixture data.
+	 *
+	 * @return void
+	 */
+	public function setUp() {
+		if (!class_exists('MongoClient')) {
+			$this->markTestSkipped('The Mongo extension is not available.');
+			return;
+		}
+		$this->getMongoDataSet()
+			->dropAllCollections()
+			->buildCollections();
+	}
+
+	/**
+	 * Cleanup after test.
+	 *
+	 * @return void
+	 */
+	public function tearDown() {
+		$this->getMongoDataSet()->dropAllCollections();
+	}
+
+	/**
+	 * Retrieve a mongo connection client.
+	 *
+	 * @return Zumba\PHPUnit\Extensions\Mongo\Client\Connector
+	 */
+	protected abstract function getMongoConnection();
+
+	/**
+	 * Retrieve a dataset object.
+	 *
+	 * @return Zumba\PHPUnit\Extensions\Mongo\DataSet\DataSet
+	 */
+	protected abstract function getMongoDataSet();
+
+}