diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 5d97be41..01ec3260 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -9,10 +9,15 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 The format of this change log follows the advice given at [Keep a CHANGELOG](http://keepachangelog.com).
 
 ## [Unreleased]
+
 ### Changed
 - Updated all uses of `actions/checkout` from `v3` (using node 16) to `v4` (using node 20), because [actions using node 16 are deprecated](https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/) and will stop working in the future.
 * ACTION SUGGESTED: In order to avoid the node 16 deprecation warnings, update your workflows to use `actions/checkout@v4`.
 
+### Deprecated
+- The `phpcpd` command (that uses the [PHP Copy/Paste Detector](https://github.com/sebastianbergmann/phpcpd), now abandoned) has been deprecated in this `moodle-plugin-ci` release (4.4.0) and will be removed in 5.0.0. No replacement is planned.
+- ACTION SUGGESTED: In order to avoid deprecation warnings or annotations, proceed to remove this command from your workflows. Note that any use will throw an error in the next major release (5.0.0).
+
 ## [4.3.2] - 2024-01-26
 ### Changed
 - Modified internal CI scripts towards better Codecov future support.
diff --git a/docs/CLI.md b/docs/CLI.md
index 20a0ef9f..df8a3bb5 100644
--- a/docs/CLI.md
+++ b/docs/CLI.md
@@ -19,7 +19,7 @@ title: Moodle Plugin CI Commands
 * [`mustache`](#mustache)
 * [`parallel`](#parallel)
 * [`phpcbf`](#phpcbf)
-* [`phpcpd` (DEPRECATED)](#phpcpd)
+* [`phpcpd`](#phpcpd)
 * [`phpcs`](#phpcs)
 * [`phpdoc`](#phpdoc)
 * [`phplint`](#phplint)
@@ -1485,21 +1485,13 @@ Do not ask any interactive question
 `phpcpd`
 --------
 
-Run PHP Copy/Paste Detector on a plugin.
-
-### Deprecation Notice
-
-[PHP Copy/Paste Detector](https://github.com/sebastianbergmann/phpcpd) has been abandoned by its maintainers.
-
-The integration with it will be removed without replacement from future versions of this plugin.
-
-_Usage of the `phpcpd` command is discouraged._
+Run PHP Copy/Paste Detector on a plugin (**DEPRECATED**)
 
 ### Usage
 
 * `phpcpd <plugin>`
 
-Run PHP Copy/Paste Detector on a plugin
+Run PHP Copy/Paste Detector on a plugin (**DEPRECATED**)
 
 ### Arguments
 
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index eb8d20bc..b32a19e0 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -11,4 +11,7 @@
       <directory suffix=".php">./src/</directory>
     </include>
   </coverage>
+  <php>
+    <const name="PHPUNIT_TEST" value="true"/>
+  </php>
 </phpunit>
diff --git a/src/Command/CopyPasteDetectorCommand.php b/src/Command/CopyPasteDetectorCommand.php
index 8d9b6e25..634d08fb 100644
--- a/src/Command/CopyPasteDetectorCommand.php
+++ b/src/Command/CopyPasteDetectorCommand.php
@@ -24,7 +24,7 @@
 /**
  * Run PHP Copy/Paste Detector on a plugin.
  *
- * @deprecated
+ * @deprecated Since 4.4.0, to be removed in 5.0.0. No replacement is planned.
  */
 class CopyPasteDetectorCommand extends AbstractPluginCommand
 {
@@ -33,11 +33,25 @@ protected function configure(): void
         parent::configure();
 
         $this->setName('phpcpd')
-            ->setDescription('Run PHP Copy/Paste Detector on a plugin (DEPRECATED)');
+            ->setDescription('Run PHP Copy/Paste Detector on a plugin (**DEPRECATED**)');
     }
 
     protected function execute(InputInterface $input, OutputInterface $output): int
     {
+        if (!defined('PHPUNIT_TEST')) { // Only show deprecation warnings in non-test environments.
+            trigger_deprecation(
+                'moodle-plugin-ci',
+                '4,4,0',
+                'The "%s" command is deprecated and will be removed in %s. No replacement is planned.',
+                $this->getName(),
+                '5.0.0'
+            );
+            if (getenv('GITHUB_ACTIONS')) { // Only show deprecation annotations in GitHub Actions.
+                echo '::warning title=Deprecated command::The phpcpd command ' .
+                    'is deprecated and will be removed in 5.0.0. No replacement is planned.' . PHP_EOL;
+            }
+        }
+
         $timer = new Timer();
         $timer->start();