[3.1] Allow DotenvFactory to accept an empty array of adapters

src/Environment/DotenvFactory.php

@@ -31,7 +31,7 @@ class DotenvFactory implements FactoryInterface
      */
     public function __construct(array $adapters = null)
     {
-        $this->adapters = array_filter($adapters ?: [new ApacheAdapter(), new EnvConstAdapter(), new ServerConstAdapter(), new PutenvAdapter()], function (AdapterInterface $adapter) {
+        $this->adapters = array_filter($adapters === null ? [new ApacheAdapter(), new EnvConstAdapter(), new ServerConstAdapter(), new PutenvAdapter()] : $adapters, function (AdapterInterface $adapter) {
             return $adapter->isSupported();
         });
     }

tests/Dotenv/FactoryTest.php

@@ -0,0 +1,44 @@
+<?php
+
+use Dotenv\Environment\Adapter\EnvConstAdapter;
+use Dotenv\Environment\DotenvFactory;
+use PHPUnit\Framework\TestCase;
+
+class FactoryTest extends TestCase
+{
+    private static function getAdapters($obj)
+    {
+        $prop = (new ReflectionClass($obj))->getProperty('adapters');
+
+        $prop->setAccessible(true);
+
+        return $prop->getValue($obj);
+    }
+
+    public function testDefaults()
+    {
+        $f = new DotenvFactory();
+
+        $this->assertInstanceOf('Dotenv\Environment\FactoryInterface', $f);
+        $this->assertCount(3, self::getAdapters($f->create()));
+        $this->assertCount(3, self::getAdapters($f->createImmutable()));
+    }
+
+    public function testSingle()
+    {
+        $f = new DotenvFactory([new EnvConstAdapter()]);
+
+        $this->assertInstanceOf('Dotenv\Environment\FactoryInterface', $f);
+        $this->assertCount(1, self::getAdapters($f->create()));
+        $this->assertCount(1, self::getAdapters($f->createImmutable()));
+    }
+
+    public function testNone()
+    {
+        $f = new DotenvFactory([]);
+
+        $this->assertInstanceOf('Dotenv\Environment\FactoryInterface', $f);
+        $this->assertCount(0, self::getAdapters($f->create()));
+        $this->assertCount(0, self::getAdapters($f->createImmutable()));
+    }
+}