added failing test for yiisoft#6547

tests/unit/extensions/redis/RedisCacheTest.php

@@ -87,6 +87,30 @@ public function testLargeData()
         $this->assertTrue($cache->get($key) === $data);
     }
 
+    /**
+     * Store a megabyte and see how it goes
+     * https://github.com/yiisoft/yii2/issues/6547
+     */
+    public function testReallyLargeData()
+    {
+        $cache = $this->getCacheInstance();
+
+        $keys = [];
+        for($i = 1; $i < 16; $i++) {
+            $key = 'realbigdata' . $i;
+            $data = str_repeat('X', 100 * 1024); // 100 KB
+            $keys[$key] = $data;
+
+//            $this->assertTrue($cache->get($key) === false); // do not display 100KB in terminal if this fails :)
+            $cache->set($key, $data);
+        }
+        $values = $cache->mget(array_keys($keys));
+        foreach($keys as $key => $value) {
+            $this->assertArrayHasKey($key, $values);
+            $this->assertTrue($values[$key] === $value);
+        }
+    }
+
     public function testMultiByteGetAndSet()
     {
         $cache = $this->getCacheInstance();