Add test for checking ttl

Author: seregazhuk

tests/CacheTest.php

@@ -24,6 +24,16 @@ public function it_stores_and_retrieves_values(): void
         $this->assertPromiseFulfillsWith($this->cache->get('key'), 'test');
     }
 
+    /** @test */
+    public function it_stores_values_with_ttl(): void
+    {
+        $this->waitForPromise($this->cache->set('key', 'test', 1));
+
+        sleep(1);
+
+        $this->assertPromiseRejectsWith($this->cache->get('key'), Exception::class);
+    }
+
     /** @test */
     public function it_rejects_promise_when_retrieving_non_existing_key(): void
     {