Separate memory limit formatting from retrieval

This addresses vimeo#6030 (comment)

Previously PHP would allow to set memory limit to be below current
memory usage, and the test changed in this PR abused that. As we
actually don't need to test `ini_get()` value decoding was split into
its own method, and we're testing that decoding instead.

src/Psalm/Internal/CliUtils.php

@@ -589,7 +589,12 @@ public static function getPathToConfig(array $options): ?string
      */
     public static function getMemoryLimitInBytes(): int
     {
-        $limit = ini_get('memory_limit');
+        return self::convertMemoryLimitToBytes(ini_get('memory_limit'));
+    }
+
+    /** @psalm-pure */
+    public static function convertMemoryLimitToBytes(string $limit): int
+    {
         // for unlimited = -1
         if ($limit < 0) {
             return -1;

tests/CommandFunctions/GetMemoryLimitInBytesTest.php

@@ -1,27 +1,11 @@
 <?php
+
 namespace Psalm\Tests\CommandFunctions;
 
 use Psalm\Internal\CliUtils;
 
-use function ini_get;
-use function ini_set;
-
-/**
- * testcase for src/command_functions.php
- */
 class GetMemoryLimitInBytesTest extends \Psalm\Tests\TestCase
 {
-    /**
-     * @var string
-     */
-    private $previousLimit;
-
-    public function setUp(): void
-    {
-        $this->previousLimit = (string)ini_get('memory_limit');
-        parent::setUp();
-    }
-
     /**
      * @return array<int,array<string|int>>
      */
@@ -56,19 +40,15 @@ public function memoryLimitSettingProvider(): array
      *
      * @param int|string $setting
      * @param int|string $expectedBytes
-     *
      */
     public function testGetMemoryLimitInBytes(
         $setting,
         $expectedBytes
     ): void {
-        ini_set('memory_limit', (string)$setting);
-        $this->assertSame($expectedBytes, CliUtils::getMemoryLimitInBytes(), 'Memory limit in bytes does not fit setting');
-    }
-
-    public function tearDown(): void
-    {
-        ini_set('memory_limit', $this->previousLimit);
-        parent::tearDown();
+        $this->assertSame(
+            $expectedBytes,
+            CliUtils::convertMemoryLimitToBytes((string)$setting),
+            'Memory limit in bytes does not fit setting'
+        );
     }
 }