Add a few more count esque functions to not decrement against (#640)

* Add a few more count esque functions

They dont need decrementing for the same reason as count functions.

* Wrap COUNT_NAMES

* Add test cases for new comparisons

src/Mutator/Number/DecrementInteger.php

@@ -43,7 +43,14 @@
  */
 final class DecrementInteger extends AbstractNumberMutator
 {
-    private const COUNT_NAMES = ['count', 'sizeof'];
+    private const COUNT_NAMES = [
+        'count',
+        'grapheme_strlen',
+        'iconv_strlen',
+        'mb_strlen',
+        'sizeof',
+        'strlen',
+    ];
 
     /**
      * Decrements an integer by 1

tests/Mutator/Number/DecrementIntegerTest.php

@@ -320,6 +320,51 @@ public function provideMutationCases(): array
 <?php
 
 $foo = 1;
+PHP
+            ],
+            'It does not decrement zero when it is being compared as identical with result of grapheme_strlen()' => [
+                <<<'PHP'
+<?php
+
+if (grapheme_strlen($a) === 0) {
+    echo 'bar';
+}
+PHP
+            ],
+            'It does not decrement zero when it is being compared as identical with result of iconv_strlen()' => [
+                <<<'PHP'
+<?php
+
+if (iconv_strlen($a) === 0) {
+    echo 'bar';
+}
+PHP
+            ],
+            'It does not decrement zero when it is being compared as identical with result of mb_strlen()' => [
+                <<<'PHP'
+<?php
+
+if (mb_strlen($a) === 0) {
+    echo 'bar';
+}
+PHP
+            ],
+            'It does not decrement zero when it is being compared as identical with result of sizeof()' => [
+                <<<'PHP'
+<?php
+
+if (sizeof($a) === 0) {
+    echo 'bar';
+}
+PHP
+            ],
+            'It does not decrement zero when it is being compared as identical with result of strlen()' => [
+                <<<'PHP'
+<?php
+
+if (strlen($a) === 0) {
+    echo 'bar';
+}
 PHP
             ],
         ];