Allow PHP 8 (#10)

Author: keradus

composer.json

@@ -10,11 +10,11 @@
         }
     ],
     "require": {
-        "php": "^5.5 || ^7.0",
+        "php": "^5.5 || ^7.0 || ^8.0",
         "phpunit/phpunit": "^4.0 || ^5.3 || ^6.0 || ^7.0 || ^8.0"
     },
     "require-dev": {
-        "friendsofphp/php-cs-fixer": "^2.12"
+        "friendsofphp/php-cs-fixer": "^2.16"
     },
     "conflict": {
         "hhvm": "*"

src/PolyfillTrait.php

@@ -18,7 +18,7 @@ trait PolyfillTrait
     {
         public function expectException($exception)
         {
-            if (is_callable(['parent', 'expectException'])) {
+            if (\is_callable(['parent', 'expectException'])) {
                 parent::expectException($exception);
             } else {
                 $this->setExpectedException($exception);

src/PolyfillTrait7.php

@@ -20,7 +20,7 @@ trait PolyfillTrait7
 {
     public function expectException(string $exception): void
     {
-        if (is_callable(['parent', 'expectException'])) {
+        if (\is_callable(['parent', 'expectException'])) {
             parent::expectException($exception);
         } else {
             $this->setExpectedException($exception);