Added AsyncMilliSleepExceptionHandler and accompanying test.

Upgraded PHPUnit 4.8 -> 6.
Changed PHP minimum version from 5.5 -> 7.0.

Author: Bilge

.gitignore

@@ -1,2 +1,3 @@
 /vendor/
 /.*/
+/composer.lock

.travis.yml

@@ -6,11 +6,10 @@ sudo: false
 language: php
 
 php:
-  - 5.5
-  - 5.6
   - 7.0
   - 7.1
   - 7.2
+  - 7.3
 
 env:
   matrix:

composer.json

@@ -8,10 +8,12 @@
     }
   ],
   "require": {
+    "php": "^7",
     "scriptfusion/retry": "^1|^2"
   },
   "require-dev": {
-    "phpunit/phpunit": "^4.8"
+    "phpunit/phpunit": "^6",
+    "amphp/amp": "^2"
   },
   "autoload": {
     "psr-4": {

src/AsyncMilliSleepExceptionHandler.php

@@ -0,0 +1,28 @@
+<?php
+declare(strict_types=1);
+
+namespace ScriptFUSION\Retry\ExceptionHandler;
+
+use Amp\Delayed;
+
+/**
+ * Delays for a series of millisecond delays on each invocation.
+ */
+class AsyncMilliSleepExceptionHandler
+{
+    private $delays;
+
+    public function __construct(\Iterator $delays)
+    {
+        $this->delays = $delays;
+    }
+
+    public function __invoke()
+    {
+        $delay = $this->delays->current();
+
+        $this->delays->next();
+
+        return new Delayed($delay);
+    }
+}

src/ExponentialBackoffExceptionHandler.php

@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace ScriptFUSION\Retry\ExceptionHandler;
 
 use ScriptFUSION\Retry\ExceptionHandler\Sequence\PowersOfTwoSequence;
@@ -15,11 +16,11 @@ class ExponentialBackoffExceptionHandler extends MicroSleepExceptionHandler
     public function __construct($microTimeCoefficient = self::DEFAULT_COEFFICIENT)
     {
         parent::__construct($this->generateSequence(
-            $this->microTimeCoefficient = $microTimeCoefficient|0
+            $this->microTimeCoefficient = $microTimeCoefficient | 0
         ));
     }
 
-    private function generateSequence($coefficient)
+    private function generateSequence($coefficient): \Generator
     {
         foreach (new PowersOfTwoSequence as $base) {
             yield $base * $coefficient;

src/MicroSleepExceptionHandler.php

@@ -1,8 +1,9 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace ScriptFUSION\Retry\ExceptionHandler;
 
 /**
- * Sleeps for a series of microsecond delays for each invocation.
+ * Sleeps for a series of microsecond delays on each invocation.
  */
 class MicroSleepExceptionHandler
 {

src/Sequence/PowersOfTwoSequence.php

@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace ScriptFUSION\Retry\ExceptionHandler\Sequence;
 
 final class PowersOfTwoSequence implements \IteratorAggregate

test/Unit/AsyncMilliSleepExceptionHandlerTest.php

@@ -0,0 +1,40 @@
+<?php
+declare(strict_types=1);
+
+namespace ScriptFUSIONTest\Retry\ExceptionHandler\Unit;
+
+use PHPUnit\Framework\TestCase;
+use ScriptFUSION\Retry\ExceptionHandler\AsyncMilliSleepExceptionHandler;
+
+/**
+ * @see AsyncMilliSleepExceptionHandler
+ */
+final class AsyncMilliSleepExceptionHandlerTest extends TestCase
+{
+    public function testValue()
+    {
+        $handler = new AsyncMilliSleepExceptionHandler(new \ArrayIterator([1000]));
+
+        $start = microtime(true);
+        \Amp\Promise\wait($handler());
+
+        self::assertGreaterThan($start + 1, microtime(true));
+    }
+
+    public function testSeries()
+    {
+        $handler = new AsyncMilliSleepExceptionHandler(
+            new \ArrayIterator($delays = array_fill(0, $limit = 10, 100))
+        );
+
+        $start = microtime(true);
+
+        \Amp\Loop::run(static function () use ($handler, $limit): \Generator {
+            for ($counter = 0; $counter < $limit; ++$counter) {
+                yield $handler();
+            }
+        });
+
+        self::assertGreaterThan($start + 1, microtime(true));
+    }
+}

test/Unit/ExponentialBackoffExceptionHandlerTest.php

@@ -1,9 +1,11 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace ScriptFUSIONTest\Retry\Unit\ExceptionHandler;
 
+use PHPUnit\Framework\TestCase;
 use ScriptFUSION\Retry\ExceptionHandler\ExponentialBackoffExceptionHandler;
 
-final class ExponentialBackoffExceptionHandlerTest extends \PHPUnit_Framework_TestCase
+final class ExponentialBackoffExceptionHandlerTest extends TestCase
 {
     public function test()
     {

test/Unit/MicroSleepExceptionHandlerTest.php

@@ -1,9 +1,11 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace ScriptFUSIONTest\Retry\Unit\ExceptionHandler;
 
+use PHPUnit\Framework\TestCase;
 use ScriptFUSION\Retry\ExceptionHandler\MicroSleepExceptionHandler;
 
-final class MicroSleepExceptionHandlerTest extends \PHPUnit_Framework_TestCase
+final class MicroSleepExceptionHandlerTest extends TestCase
 {
     public function testValue()
     {

test/Unit/Sequence/PowersOfTwoSequenceTest.php

@@ -1,9 +1,11 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace ScriptFUSIONTest\Retry\Unit\ExceptionHandler\Sequence;
 
+use PHPUnit\Framework\TestCase;
 use ScriptFUSION\Retry\ExceptionHandler\Sequence\PowersOfTwoSequence;
 
-final class PowersOfTwoSequenceTest extends \PHPUnit_Framework_TestCase
+final class PowersOfTwoSequenceTest extends TestCase
 {
     public function testSequence()
     {