add phpstan support

Author: doganoo

composer.json

@@ -24,6 +24,7 @@
   "require-dev": {
     "ergebnis/composer-normalize": "^2.9",
     "phpcompatibility/php-compatibility": "^9.3",
+    "phpstan/phpstan": "^0.12.54",
     "phpunit/phpunit": "6.5",
     "squizlabs/php_codesniffer": "^3.5"
   },
@@ -34,6 +35,7 @@
     }
   },
   "scripts": {
-    "run-test": "vendor/bin/phpunit tests"
+    "run-test": "vendor/bin/phpunit tests",
+    "phpstan": "vendor/bin/phpstan analyse --level=8 --memory-limit=2G src tests"
   }
 }

composer.lock

@@ -0,0 +1,2 @@
+parameters:
+	checkMissingIterableValueType: false

phpstan.neon

@@ -41,7 +41,7 @@ class EnumTest extends TestCase {
      * @throws NullNotAllowedException
      * @throws ValueNotAllowedException
      */
-    public function testEnum() {
+    public function testEnum(): void {
         $enum     = new Enum([
             "1"
             , "2"

tests/Various/EnumTest.php

@@ -32,7 +32,7 @@
 class PermutationTest extends TestCase {
 
 
-    public function testStringPermutation() {
+    public function testStringPermutation(): void {
         $permutation  = new Permutation();
         $permutations = $permutation->stringPermutations("abcd");
         $this->assertTrue(24 === \count($permutations));
@@ -46,7 +46,7 @@ public function testStringPermutation() {
         $this->assertTrue(1 === \count($permutations));
     }
 
-    public function testNumberPermutation() {
+    public function testNumberPermutation(): void {
         $permutation  = new Permutation();
         $permutations = $permutation->numberPermutations(1234);
         $this->assertTrue(24 === \count($permutations));