Refactored main class, improved a few things here and there. Looks polished enough

tests/ExampleClass.php

@@ -3,57 +3,44 @@
     class ExampleClass
     {
         /**
-         * @var array
+         * Sleeps for the given number of seconds, plus a random number of seconds between 0 and 100.
+         *
+         * @param int $seconds
+         * @return int
+         * @throws Exception
          */
-        private $data;
-
-        /**
-         * ExampleClass constructor.
-         */
-        public function __construct()
+        public function sleep(int $seconds=1): int
         {
-            $this->data = [];
+            sleep($seconds);
+            return random_int(0, 100) + $seconds;
         }
 
         /**
-         * Sets a value in the data array
+         * Calculates pi using the Leibniz formula.
+         *
+         * @param int $iterations
+         * @return float
+         */
+        public function pi(int $iterations): float
+        {
+            $pi = 0;
+            $sign = 1;
+            for ($i = 0; $i < $iterations; $i++)
+            {
+                $pi += $sign / (2 * $i + 1);
+                $sign *= -1;
+            }
+            return $pi * 4;
+        }
+
+        /**
+         * Throws an exception.
          *
-         * @param string $key
-         * @param mixed $value
          * @return void
+         * @throws Exception
          */
-        public function set(string $key, mixed $value): void
+        public function throwException(): void
         {
-            $this->data[$key] = $value;
-        }
-
-        /**
-         * Gets a value from the data array
-         *
-         * @param string $key
-         * @return mixed
-         */
-        public function get(string $key): mixed
-        {
-            return $this->data[$key];
-        }
-
-        /**
-         * Checks if a key exists in the data array
-         *
-         * @param string $key
-         * @return bool
-         */
-        public function exists(string $key): bool
-        {
-            return isset($this->data[$key]);
-        }
-
-        /**
-         * @return void
-         */
-        public function clear(): void
-        {
-            $this->data = [];
+            throw new Exception('This is an exception.');
         }
     }