Issue #3139465 by alexshipilov, osab: Replace assertions involving calls to...

Issue #3139465 by alexshipilov, osab: Replace assertions involving calls to is_file with assertFileExists()/assertFileNotExists()

tests/src/Kernel/ImageOptimizePipelineTest.php

@@ -190,7 +190,7 @@ class ImageOptimizePipelineTest extends KernelTestBase {
     }
 
     file_put_contents($filepath, $contents);
-    $this->assertTrue(is_file($filepath), t('The test file exists on the disk.'));
+    $this->assertFileExists($filepath, t('The test file exists on the disk.'));
     return $filepath;
   }
 
@@ -201,7 +201,7 @@ class ImageOptimizePipelineTest extends KernelTestBase {
 
     // Include special characters in the filename.
     $image_uri = file_default_scheme() . '://Файл для тестирования ' . $this->randomMachineName() . '.png';
-    $this->assertFalse(is_file($image_uri), t('The test file does not exist on the disk.'));
+    $this->assertFileNotExists($image_uri, t('The test file does not exist on the disk.'));
 
     // Setup our pipeline.
     $pipeline = ImageAPIOptimizePipeline::create([