diff --git a/classes/workflow_manager.php b/classes/workflow_manager.php
index f5729ca..8f7fff7 100644
--- a/classes/workflow_manager.php
+++ b/classes/workflow_manager.php
@@ -235,6 +235,9 @@ public function get_step_class_names($steptype = null) {
             ]
         ];
         foreach ($plugins as $plugin => $dir) {
+            if (!PHPUNIT_TEST && $plugin == 'testplugin') {
+                continue;
+            }
             $dirs[] = (object)[
                 'path' => $dir . '/classes',
                 'namespace' => "trigger_$plugin",
diff --git a/custom/testplugin/classes/steps/lookups/subplugin_lookup_test_step.php b/custom/testplugin/classes/steps/lookups/subplugin_lookup_test_step.php
new file mode 100644
index 0000000..39b5784
--- /dev/null
+++ b/custom/testplugin/classes/steps/lookups/subplugin_lookup_test_step.php
@@ -0,0 +1,91 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace trigger_testplugin\steps\lookups;
+use tool_trigger\steps\lookups\base_lookup_step;
+
+/**
+ * A lookup step for testing purposes.
+ *
+ * @package     trigger_testplugin
+ * @copyright   2025 Moodle US
+ * @author      Oscar Nadjar <oscar.nadjar@moodle.com>
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class subplugin_lookup_test_step extends base_lookup_step {
+
+    /**
+     * The fields supplied by this step.
+     * A string containing all the cohorts a user is assigned to.
+     *
+     * @var array
+     */
+    private static $stepfields = array(
+        'testlookupresult'
+    );
+
+    protected function init() {
+    }
+
+    /**
+     * {@inheritDoc}
+     * @see \tool_trigger\steps\base\base_step::execute()
+     */
+    public function execute($step, $trigger, $event, $stepresults) {
+        global $DB;
+        $stepresults = [ 'testlookupresult' => 'test' ];
+        return [true, $stepresults];
+    }
+
+    /**
+     * {@inheritDoc}
+     * @see \tool_trigger\steps\base\base_step::form_definition_extra()
+     */
+    public function form_definition_extra($form, $mform, $customdata) {
+    }
+
+    /**
+     * {@inheritDoc}
+     * @see \tool_trigger\steps\base\base_step::get_step_desc()
+     */
+    public static function get_step_desc() {
+        return get_string('subplugin_lookup_test_step_desc', 'trigger_testplugin');
+    }
+
+    /**
+     * {@inheritDoc}
+     * @see \tool_trigger\steps\base\base_step::get_step_name()
+     */
+    public static function get_step_name() {
+        return get_string('subplugin_lookup_test_step_name', 'trigger_testplugin');
+    }
+
+    /**
+     * {@inheritDoc}
+     * @see \tool_trigger\steps\base\base_step::get_privacyfields()
+     */
+    public static function get_privacyfields() {
+    }
+
+    /**
+     * Get a list of fields this step provides.
+     *
+     * @return array $stepfields The fields this step provides.
+     */
+    public static function get_fields() {
+        return self::$stepfields;
+    }
+}
diff --git a/custom/testplugin/lang/en/trigger_testplugin.php b/custom/testplugin/lang/en/trigger_testplugin.php
new file mode 100755
index 0000000..a3cf314
--- /dev/null
+++ b/custom/testplugin/lang/en/trigger_testplugin.php
@@ -0,0 +1,31 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Language file for trigger_testplugin.
+ *
+ * @package     trigger_testplugin
+ * @copyright   2025 Moodle US
+ * @author      Oscar Nadjar <oscar.nadjar@moodle.com>
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+$string['pluginname'] = 'Test Trigger Subplugin';
+$string['pluginname_help'] = 'This plugin is used for testing the subplugin functionality of the Tool Trigger plugin.';
+$string['subplugin_lookup_test_step_desc'] = 'This is a test subplugin step for the Tool Trigger plugin. It is used to test the functionality of the subplugin system.';
+$string['subplugin_lookup_test_step_name'] = 'Test Subplugin Step';
diff --git a/custom/testplugin/version.php b/custom/testplugin/version.php
new file mode 100755
index 0000000..84c2021
--- /dev/null
+++ b/custom/testplugin/version.php
@@ -0,0 +1,33 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Plugin version and other meta-data are defined here.
+ *
+ * @package     trigger_testplugin
+ * @copyright   2025 Moodle US
+ * @author      Oscar Nadjar <oscar.nadjar@moodle.com>
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+$plugin->component = 'trigger_testplugin';
+$plugin->version  = 2025042200;
+$plugin->requires = 2021051701;
+$plugin->supported = [404, 405];
+$plugin->maturity = MATURITY_STABLE;
+$plugin->release = '1.0.0';
diff --git a/tests/subplugin_step_test.php b/tests/subplugin_step_test.php
new file mode 100644
index 0000000..9e9d9fd
--- /dev/null
+++ b/tests/subplugin_step_test.php
@@ -0,0 +1,78 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * "Fail" filter step's unit tests.
+ *
+ * @package    tool_trigger
+ * @author     Aaron Wells <aaronw@catalyst.net.nz>
+ * @copyright  Catalyst IT 2018
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace tool_trigger;
+
+defined('MOODLE_INTERNAL') || die();
+
+global $CFG;
+
+class subplugin_step_test extends \advanced_testcase {
+   
+    /**
+     * Test user.
+     * @var
+     */
+    protected $user;
+
+    /**
+     * Test event.
+     * @var
+     */
+    protected $event;
+
+    /**
+     * Create an event to use for testing.
+     */
+    public function setup():void {
+
+        // Create a user event.
+        $this->user = \core_user::get_user_by_username('admin');
+        $this->event = \core\event\user_profile_viewed::create([
+            'objectid' => $this->user->id,
+            'relateduserid' => $this->user->id,
+            'context' => \context_user::instance($this->user->id),
+            'other' => [
+                'courseid' => 1,
+                'courseshortname' => 'short name',
+                'coursefullname' => 'full name'
+            ]
+        ]);
+    }
+
+    /**
+     * Basic use-case, with default values for settings. Find the
+     * user identified at "userid", and add their data with the
+     * prefix "user_".
+     */
+    public function test_execute_basic() {
+        $step = new \trigger_testplugin\steps\lookups\subplugin_lookup_test_step(json_encode([]));
+
+        list($status, $stepresults) = $step->execute(null, null, $this->event, []);
+
+        $this->assertTrue($status);
+        $this->assertEquals('test', $stepresults['testlookupresult']);
+    }
+}
diff --git a/tests/workflow_manager_test.php b/tests/workflow_manager_test.php
index 491652a..884b9fa 100644
--- a/tests/workflow_manager_test.php
+++ b/tests/workflow_manager_test.php
@@ -79,6 +79,20 @@ public function test_get_steps_by_type() {
         );
     }
 
+    /**
+     * Test getting step from custom plugin.
+     */
+    public function test_custom_step_names() {
+
+        $stepclasses = ['\trigger_testplugin\steps\lookups\subplugin_lookup_test_step'];
+        $stepobj = new \tool_trigger\workflow_manager();
+        $steps = $stepobj->lookup_step_names($stepclasses);
+        $this->assertEquals(
+                get_string('subplugin_lookup_test_step_name', 'trigger_testplugin'),
+                $steps['\trigger_testplugin\steps\lookups\subplugin_lookup_test_step']
+        );
+    }
+
     /**
      * Test the code for validating the name of a step class and instantiating it.
      *