diff --git a/core/modules/file/src/Plugin/Field/FieldType/FileItemMaxFileSizeValidator.php b/core/modules/file/src/Plugin/Field/FieldType/FileItemMaxFileSizeValidator.php
index 6cb2fdb52d..713cf743af 100644
--- a/core/modules/file/src/Plugin/Field/FieldType/FileItemMaxFileSizeValidator.php
+++ b/core/modules/file/src/Plugin/Field/FieldType/FileItemMaxFileSizeValidator.php
@@ -57,9 +57,10 @@ class FileItemMaxFileSizeValidator {
   }

   /**
-   * Validate the given string looks like a byte size string.
+   * Validates the given string looks like a byte size string.
    *
    * @return bool
+   *   TRUE if size is a valid byte size string, FALSE if not.
    */
   private static function sizeIsValidByteString() {
     return (
@@ -70,7 +71,7 @@ class FileItemMaxFileSizeValidator {
   }

   /**
-   * Strips spaces from a string of text.
+   * Strips whitespace from a string of text.
    *
    * @param string $string
    *   A string representing a size (5mb, 500GB etc)
@@ -119,14 +120,13 @@ class FileItemMaxFileSizeValidator {
    *   TRUE if string can be parsed by Bytes::toInt(), FALSE otherwise.
    */
   private static function toIntCanParseString() {
-    $valid = TRUE;
     try {
       Bytes::toInt(self::$size);
     }
     catch (\Exception $e) {
-      $valid = FALSE;
+      return FALSE;
     }
-    return $valid;
+    return TRUE;
   }

 }
diff --git a/core/modules/file/tests/src/Unit/FileItemFieldSettingsFormTest.php b/core/modules/file/tests/src/Unit/FileItemFieldSettingsFormTest.php
index d8f7696a2a..65de0d88dd 100644
--- a/core/modules/file/tests/src/Unit/FileItemFieldSettingsFormTest.php
+++ b/core/modules/file/tests/src/Unit/FileItemFieldSettingsFormTest.php
@@ -47,7 +47,7 @@ class FileItemFieldSettingsFormTest extends UnitTestCase {
    *   Array of inputs and error expectations.
    */
   public function maxFileSizeInputsProvider() {
-    return [
+    $data = [
       ['0 bytes', FALSE],
       ['123456.03 ', TRUE],
       ['   ', FALSE],
@@ -55,7 +55,6 @@ class FileItemFieldSettingsFormTest extends UnitTestCase {
       ['0 K', FALSE],
       ['100bytes', FALSE],
       ['10000', FALSE],
-      ['100bytes', FALSE],
       ['100 bytes', FALSE],
       ['999989 bytes', FALSE],
       ['999989bytes', FALSE],
@@ -87,6 +86,17 @@ class FileItemFieldSettingsFormTest extends UnitTestCase {
       [' 123456.03', TRUE],
       [' some words & stuff', TRUE],
     ];
+
+    // Improve test output by using the input value as a label for the dataset.
+    foreach ($data as $index => $item) {
+      // If the index looks like an in eg "1000" "2" etc, php still detects
+      // it as a numeric index. Adding text to all the labels to force them
+      // to render.
+      $data["Sample input: '{$item[0]}'"] = $item;
+      unset($data[$index]);
+    }
+
+    return $data;
   }

 }