DropDatabase functional tests

tests/Operation/DropDatabaseFunctionalTest.php

+<?php
+
+namespace MongoDB\Tests\Operation;
+
+use MongoDB\Driver\Server;
+use MongoDB\Operation\DropDatabase;
+use MongoDB\Operation\ListDatabases;
+
+class DropDatabaseFunctionalTest extends FunctionalTestCase
+{
+    public function testDropExistingDatabase()
+    {
+        $writeResult = $this->manager->executeInsert($this->getNamespace(), array('x' => 1));
+        $this->assertEquals(1, $writeResult->getInsertedCount());
+
+        $server = $this->getPrimaryServer();
+        $operation = new DropDatabase($this->getDatabaseName());
+        $operation->execute($server);
+
+        $this->assertDatabaseDoesNotExist($server, $this->getDatabaseName());
+    }
+
+    /**
+     * @depends testDropExistingDatabase
+     */
+    public function testDropNonexistentDatabase()
+    {
+        $server = $this->getPrimaryServer();
+
+        $this->assertDatabaseDoesNotExist($server, $this->getDatabaseName());
+
+        $operation = new DropDatabase($this->getDatabaseName());
+        $operation->execute($server);
+    }
+
+    /**
+     * Asserts that a database with the given name does not exist on the server.
+     *
+     * @param Server $server
+     * @param string $databaseName
+     */
+    private function assertDatabaseDoesNotExist(Server $server, $databaseName)
+    {
+        $operation = new ListDatabases();
+        $databases = $operation->execute($server);
+
+        $foundDatabase = null;
+
+        foreach ($databases as $database) {
+            if ($database->getName() === $databaseName) {
+                $foundDatabase = $database;
+                break;
+            }
+        }
+
+        $this->assertNull($foundDatabase, sprintf('Database %s exists on the server', $databaseName));
+    }
+}