Improve missing lock_factory message when no cache_directory was provided

Author: Toflar

src/Psr6Store.php

@@ -135,7 +135,7 @@ public function __construct(array $options = [])
 
         $resolver->setDefault('lock_factory', function (Options $options) {
             if (!isset($options['cache_directory'])) {
-                throw new MissingOptionsException('The cache_directory option is required unless you set the cache explicitly');
+                throw new MissingOptionsException('The cache_directory option is required unless you set the lock_factory explicitly as by default locks are also stored in the configured cache_directory.');
             }
 
             return new Factory(

tests/Psr6StoreTest.php

@@ -44,6 +44,18 @@ protected function tearDown()
         $this->store->cleanup();
     }
 
+    public function testCustomCacheWithoutLockFactory()
+    {
+        $this->expectException(MissingOptionsException::class);
+        $this->expectExceptionMessage('The cache_directory option is required unless you set the lock_factory explicitly as by default locks are also stored in the configured cache_directory.');
+
+        $cache = $this->createMock(TagAwareAdapterInterface::class);
+
+        new Psr6Store([
+            'cache' => $cache,
+        ]);
+    }
+
     public function testCustomCacheAndLockFactory()
     {
         $cache = $this->createMock(TagAwareAdapterInterface::class);