LocaleTranslation should have its translation property initialized as array

+1 for moving the file.

+++ b/core/modules/locale/tests/Drupal/locale/Tests/StringTranslation/Translator/LocaleTranslationTest.phpundefined
@@ -0,0 +1,47 @@
+  /**
+   * A mocked storage to use when instantiating LocaleTranslation objects.
+   */
+  protected $storage;

You could document the type of this variable.

+++ b/core/modules/locale/tests/Drupal/locale/Tests/StringTranslation/Translator/LocaleTranslationTest.phpundefined
@@ -0,0 +1,47 @@
+  public function setUp() {

and @inheritdoc

+++ b/core/modules/locale/tests/Drupal/locale/Tests/StringTranslation/Translator/LocaleTranslationTest.phpundefined
@@ -0,0 +1,47 @@
+    $translation = new LocaleTranslation($this->storage);
+    // Prove that destruction works without errors.
+    $translation->destruct();

Can't we test what actually was done? For example assertAttributeEmpty?

@dawehner: Nothing was done, as expected. To add more tests to actually let it do something, we first need the refactoring that's happening in the cache collector issue, which will allow to inject and mock all dependencies properly. So wondering if we want to get that in first and then add more tests here, or just get it in like this and extend later.

Raising to major, this is logging a php warning to watchdog for every request you make when locale is enabled and you're using english/system language.

index 0c405dd..4957106 100644
--- a/core/modules/locale/lib/Drupal/locale/LocaleTranslation.php

--- a/core/modules/locale/lib/Drupal/locale/LocaleTranslation.php
+++ b/core/modules/locale/lib/Drupal/locale/StringTranslation/Translator/LocaleTranslation.phpundefined

Is the move to this new place arbitrary or is there any rule that this would be placed here? Seems like arbitrary based on the services association taking whatever location desired.

+++ b/core/modules/locale/tests/Drupal/locale/Tests/StringTranslation/Translator/LocaleTranslationTest.phpundefined
@@ -0,0 +1,53 @@
+      'name' => 'Locale translation tests',
+      'description' => 'Test locale module translatiob implementation.',

translatiob typo :)

Also, if there is already a webtest named like this, should we be more specific explaining what is happening here?

Yeah renaming the UI test to ...UiTest would be good :)

*UPDATED*

This patch fixed error

Warning: Invalid argument supplied for foreach() in Drupal\locale\LocaleTranslation->destruct() (line 80 of /xxx/xxx/xxx/drupal/core/modules/locale/lib/Drupal/locale/LocaleTranslation.php).

Yes, that's exactly what this fixes.

Okay, let's keep it simple for now.

Committed 90c2c23 and pushed to 8.x. Thanks!