tests: Reproduce issue in a test.

spec/loophp/collection/CollectionSpec.php

@@ -3034,6 +3034,34 @@ public function it_can_zip(): void
             ->shouldIterateAs([[1, 'A'], [2, 'B'], [3, 'C'], [4, 'D'], [5, 'E']]);
     }
 
+    /**
+     * @see https://github.com/loophp/collection/issues/57
+     */
+    public function it_fix_bug_57()
+    {
+        $input = array_combine(range(1, 26), range('a', 'z'));
+
+        $collection = $this::fromIterable($input);
+
+        $collection
+            ->key()
+            ->shouldReturn(1);
+
+        $collection
+            ->current()
+            ->shouldReturn('a');
+
+        $last = $collection->last();
+
+        $last
+            ->key()
+            ->shouldReturn(26);
+
+        $last
+            ->current()
+            ->shouldReturn('z');
+    }
+
     public function it_is_initializable(): void
     {
         $this->shouldHaveType(Collection::class);