Add strict_types to Collection test cases.

tests/TestCase/Collection/CollectionTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)

tests/TestCase/Collection/Iterator/BufferedIteratorTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)

tests/TestCase/Collection/Iterator/ExtractIteratorTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)

tests/TestCase/Collection/Iterator/FilterIteratorTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)

tests/TestCase/Collection/Iterator/InsertIteratorTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)

tests/TestCase/Collection/Iterator/MapReduceTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)

tests/TestCase/Collection/Iterator/ReplaceIteratorTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)

tests/TestCase/Collection/Iterator/SortIteratorTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)

tests/TestCase/Collection/Iterator/TreeIteratorTest.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
  * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)