docs: update external URLs

Author: kenjis

user_guide_src/source/installation/installing_manual.rst

@@ -10,7 +10,7 @@ will be your public-facing document root. Do not change anything inside the ``sy
 folder!
 
 .. note:: This is the installation technique closest to that described
-   for `CodeIgniter 3 <https://codeigniter.com/user_guide/installation/index.html>`_.
+   for `CodeIgniter 3 <https://codeigniter.com/userguide3/installation/index.html>`_.
 
 Installation
 ============

user_guide_src/source/testing/overview.rst

@@ -216,7 +216,7 @@ Ensure that a header or cookie was actually emitted::
     $this->assertHeaderEmitted("Set-Cookie: foo=bar");
 
 Note: the test case with this should be `run as a separate process
-in PHPunit <https://phpunit.readthedocs.io/en/7.4/annotations.html#runinseparateprocess>`_.
+in PHPunit <https://phpunit.readthedocs.io/en/9.5/annotations.html#runinseparateprocess>`_.
 
 **assertHeaderNotEmitted($header, $ignoreCase = false)**
 
@@ -231,7 +231,7 @@ Ensure that a header or cookie was not emitted::
     $this->assertHeaderNotEmitted("Set-Cookie: banana");
 
 Note: the test case with this should be `run as a separate process
-in PHPunit <https://phpunit.readthedocs.io/en/7.4/annotations.html#runinseparateprocess>`_.
+in PHPunit <https://phpunit.readthedocs.io/en/9.5/annotations.html#runinseparateprocess>`_.
 
 **assertCloseEnough($expected, $actual, $message = '', $tolerance = 1)**
 

user_guide_src/source/testing/response.rst

@@ -10,6 +10,10 @@ create your own directly using any ``ResponseInterface``::
     $result = new \CodeIgniter\Test\TestResponse($response);
     $result->assertOK();
 
+.. contents::
+    :local:
+    :depth: 2
+
 Testing the Response
 ====================