MigrateExecutableMemoryExceededTest has mismatched argument type mock expectations (and fails in PHPUnit8)

Seems reasonable. Thanks for fixing this up.

Committed and pushed dda035c260 to 9.0.x and da130569cb to 8.9.x and 8130c365bc to 8.8.x. Thanks!

Backported to 8.8.x as this is a test-only fix.

diff --git a/core/modules/migrate/tests/src/Unit/MigrateExecutableMemoryExceededTest.php b/core/modules/migrate/tests/src/Unit/MigrateExecutableMemoryExceededTest.php
index bce961dafa..4d80feeaa7 100644
--- a/core/modules/migrate/tests/src/Unit/MigrateExecutableMemoryExceededTest.php
+++ b/core/modules/migrate/tests/src/Unit/MigrateExecutableMemoryExceededTest.php
@@ -80,12 +80,12 @@ protected function runMemoryExceededTest($message, $memory_exceeded, $memory_usa
     if ($message) {
       $this->executable->message->expects($this->at(0))
         ->method('display')
-        ->with($this->callback(function($subject) {
+        ->with($this->callback(function ($subject) {
             return mb_stripos((string) $subject, 'reclaiming memory') !== FALSE;
         }));
       $this->executable->message->expects($this->at(1))
         ->method('display')
-        ->with($this->callback(function($subject) use ($message) {
+        ->with($this->callback(function ($subject) use ($message) {
             return mb_stripos((string) $subject, $message) !== FALSE;
         }));
     }

Fixed coding standards on commit.