add chain and stopwatch helper functions (#99)

* add chain helper function

* add stopwatch helper function

tests/ZM/GlobalFunctionsTest.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\ZM;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @internal
+ */
+class GlobalFunctionsTest extends TestCase
+{
+    public function testChain(): void
+    {
+        $mock = $this->getMockBuilder(\stdClass::class)
+            ->addMethods(['foo', 'bar', 'baz'])
+            ->getMock();
+        $mock->expects($this->once())
+            ->method('foo')
+            ->willReturn('foo');
+        $mock->expects($this->once())
+            ->method('bar')
+            ->with('foo')
+            ->willReturn('bar');
+        $mock->expects($this->once())
+            ->method('baz')
+            ->with('bar')
+            ->willReturn('baz');
+
+        $result = chain($mock)->foo()->bar(CARRY)->baz(CARRY);
+
+        $this->assertEquals('baz', $result);
+    }
+
+    public function testStopwatch(): void
+    {
+        $time = stopwatch(static function () {
+            usleep(10000);
+        });
+        $this->assertLessThan(0.1, $time);
+    }
+}