diff --git a/message/tests/migrate_message_data_task_test.php b/message/tests/migrate_message_data_task_test.php
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+++ b/message/tests/migrate_message_data_task_test.php
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+<?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/>.
+
+/**
+ * Tests the migrate message data task.
+ *
+ * @package core_message
+ * @category test
+ * @copyright 2018 Mark Nelson <markn@moodle.com>
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+global $CFG;
+
+require_once($CFG->dirroot . '/message/tests/messagelib_test.php');
+
+/**
+ * Class for testing the migrate message data task.
+ *
+ * @package core_message
+ * @category test
+ * @copyright 2018 Mark Nelson <markn@moodle.com>
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class core_message_migrate_message_data_task_testcase extends advanced_testcase {
+
+    /**
+     * Test set up.
+     *
+     * This is executed before running any test in this file.
+     */
+    public function setUp() {
+        $this->resetAfterTest();
+    }
+
+    /**
+     * Test migrating legacy messages.
+     */
+    public function test_migrating_messages() {
+        global $DB;
+
+        // Create users to test with.
+        $user1 = $this->getDataGenerator()->create_user();
+        $user2 = $this->getDataGenerator()->create_user();
+        $user3 = $this->getDataGenerator()->create_user();
+
+        // Get the current time minus some, to make sure our data is migrated accurately and just not using the current timestamp.
+        $now = time();
+        $timedeleted1 = $now - (2 * DAYSECS);
+        $timedeleted2 = $now - (2 * DAYSECS) + 1;
+        $timeread1 = $now - DAYSECS;
+        $timeread2 = $now - DAYSECS + 1;
+        $timeread3 = $now - DAYSECS + 2;
+
+        // Send messages from user 1 to user 2.
+        $m1 = $this->create_legacy_message_or_notification($user1->id, $user2->id, 1, false, $timeread1);
+        $m2 = $this->create_legacy_message_or_notification($user1->id, $user2->id, 2);
+        $m3 = $this->create_legacy_message_or_notification($user1->id, $user2->id, 3);
+
+        // Send messages from user 3 to user 1.
+        $m4 = $this->create_legacy_message_or_notification($user3->id, $user1->id, 4, false, $timeread2);
+        $m5 = $this->create_legacy_message_or_notification($user3->id, $user1->id, 5);
+        $m6 = $this->create_legacy_message_or_notification($user3->id, $user1->id, 6);
+
+        // Send messages from user 3 to user 2.
+        $m7 = $this->create_legacy_message_or_notification($user3->id, $user2->id, 7, false, $timeread3);
+        $m8 = $this->create_legacy_message_or_notification($user3->id, $user2->id, 8);
+        $m9 = $this->create_legacy_message_or_notification($user3->id, $user2->id, 9);
+
+        // Let's delete some messages, not using API here as it does not use the legacy tables.
+        $messageupdate = new stdClass();
+        $messageupdate->id = $m1;
+        $messageupdate->timeusertodeleted = $timedeleted1;
+        $DB->update_record('message_read', $messageupdate);
+
+        $messageupdate = new stdClass();
+        $messageupdate->id = $m5;
+        $messageupdate->timeuserfromdeleted = $timedeleted2;
+        $DB->update_record('message', $messageupdate);
+
+        // Now, let's execute the task for user 1.
+        $task = new \core_message\task\migrate_message_data();
+        $task->set_custom_data(
+            [
+                'userid' => $user1->id
+            ]
+        );
+        $task->execute();
+
+        // Ok, now we need to confirm all is good.
+        // Remember - we are only converting the messages related to user 1.
+        $this->assertEquals(2, $DB->count_records('message'));
+        $this->assertEquals(1, $DB->count_records('message_read'));
+        $this->assertEquals(6, $DB->count_records('messages'));
+
+        // Get the conversations.
+        $conversation1 = \core_message\api::get_conversation_between_users([$user1->id, $user2->id]);
+        $conversation2 = \core_message\api::get_conversation_between_users([$user1->id, $user3->id]);
+
+        // Confirm what we have in the messages table is correct.
+        $messages = $DB->get_records('messages', [], 'timecreated ASC');
+        $i = 1;
+        foreach ($messages as $message) {
+            $useridfrom = $user1->id;
+            $conversationid = $conversation1;
+            if ($i > 3) {
+                $useridfrom = $user3->id;
+                $conversationid = $conversation2;
+            }
+
+            if ($i == 1) {
+                $messagereadid1 = $message->id;
+                $messagedeletedid1 = $message->id;
+            } else if ($i == 4) {
+                $messagereadid2 = $message->id;
+            } else if ($i == 5) {
+                $messagedeletedid2 = $message->id;
+            }
+
+            $this->assertEquals($useridfrom, $message->useridfrom);
+            $this->assertEquals($conversationid, $message->conversationid);
+            $this->assertEquals('Subject ' . $i, $message->subject);
+            $this->assertEquals('Full message ' . $i, $message->fullmessage);
+            $this->assertEquals(FORMAT_PLAIN, $message->fullmessageformat);
+            $this->assertEquals('Full message HTML '. $i, $message->fullmessagehtml);
+            $this->assertEquals('Small message ' . $i, $message->smallmessage);
+            $this->assertEquals($i, $message->timecreated);
+            $i++;
+        }
+
+        // Confirm there are 4 actions.
+        $this->assertEquals(4, $DB->count_records('message_user_actions'));
+
+        // Confirm the messages that were marked as read have actions associated with them.
+        $muas = $DB->get_records('message_user_actions', ['action' => \core_message\api::MESSAGE_ACTION_READ], 'timecreated DESC');
+        $this->assertCount(2, $muas);
+
+        // Message user action for message read by user 1 (referring to $m4).
+        $mua1 = array_shift($muas);
+        // Message user action for message read by user 2 (referring to $m1).
+        $mua2 = array_shift($muas);
+
+        $this->assertEquals($user1->id, $mua1->userid);
+        $this->assertEquals($messagereadid2, $mua1->messageid);
+        $this->assertEquals($timeread2, $mua1->timecreated);
+
+        $this->assertEquals($user2->id, $mua2->userid);
+        $this->assertEquals($messagereadid1, $mua2->messageid);
+        $this->assertEquals($timeread1, $mua2->timecreated);
+
+        // Confirm the messages that were deleted have actions associated with them.
+        $muas = $DB->get_records('message_user_actions', ['action' => \core_message\api::MESSAGE_ACTION_DELETED],
+            'timecreated DESC');
+        $this->assertCount(2, $muas);
+
+        // Message user action for message deleted by user 3 (referring to $m5).
+        $mua1 = array_shift($muas);
+        // Message user action for message deleted by user 2 (referring to $m1).
+        $mua2 = array_shift($muas);
+
+        $this->assertEquals($user3->id, $mua1->userid);
+        $this->assertEquals($messagedeletedid2, $mua1->messageid);
+        $this->assertEquals($timedeleted2, $mua1->timecreated);
+
+        $this->assertEquals($user2->id, $mua2->userid);
+        $this->assertEquals($messagedeletedid1, $mua2->messageid);
+        $this->assertEquals($timedeleted1, $mua2->timecreated);
+    }
+
+    /**
+     * Test migrating legacy notifications.
+     */
+    public function test_migrating_notifications() {
+        global $DB;
+
+        // Create users to test with.
+        $user1 = $this->getDataGenerator()->create_user();
+        $user2 = $this->getDataGenerator()->create_user();
+        $user3 = $this->getDataGenerator()->create_user();
+
+        // Get the current time minus some, to make sure our data is migrated accurately and just not using the current timestamp.
+        $timeread = time() - DAYSECS;
+
+        // Send notifications from user 1 to user 2.
+        $this->create_legacy_message_or_notification($user1->id, $user2->id, 1, true, $timeread);
+        $this->create_legacy_message_or_notification($user1->id, $user2->id, 2, true);
+        $this->create_legacy_message_or_notification($user1->id, $user2->id, 3, true);
+
+        // Send notifications from user 3 to user 1.
+        $this->create_legacy_message_or_notification($user3->id, $user1->id, 4, true, $timeread);
+        $this->create_legacy_message_or_notification($user3->id, $user1->id, 5, true);
+        $this->create_legacy_message_or_notification($user3->id, $user1->id, 6, true);
+
+        // Send notifications from user 3 to user 2.
+        $this->create_legacy_message_or_notification($user3->id, $user2->id, 7, true, $timeread);
+        $this->create_legacy_message_or_notification($user3->id, $user2->id, 8, true);
+        $this->create_legacy_message_or_notification($user3->id, $user2->id, 9, true);
+
+        // Now, let's execute the task for user 1.
+        $task = new \core_message\task\migrate_message_data();
+        $task->set_custom_data(
+            [
+                'userid' => $user1->id
+            ]
+        );
+        $task->execute();
+
+        // Ok, now we need to confirm all is good.
+        // Remember - we are only converting the notifications related to user 1.
+        $this->assertEquals(2, $DB->count_records('message'));
+        $this->assertEquals(1, $DB->count_records('message_read'));
+        $this->assertEquals(6, $DB->count_records('notifications'));
+
+        // Confirm what we have in the notifications table is correct.
+        $notifications = $DB->get_records('notifications', [], 'timecreated ASC');
+        $i = 1;
+        foreach ($notifications as $notification) {
+            $useridfrom = $user1->id;
+            $useridto = $user2->id;
+            if ($i > 3) {
+                $useridfrom = $user3->id;
+                $useridto = $user1->id;
+            }
+
+            $this->assertEquals($useridfrom, $notification->useridfrom);
+            $this->assertEquals($useridto, $notification->useridto);
+            $this->assertEquals('Subject ' . $i, $notification->subject);
+            $this->assertEquals('Full message ' . $i, $notification->fullmessage);
+            $this->assertEquals(FORMAT_PLAIN, $notification->fullmessageformat);
+            $this->assertEquals('Full message HTML '. $i, $notification->fullmessagehtml);
+            $this->assertEquals('Small message ' . $i, $notification->smallmessage);
+            $this->assertEquals('mod_assign', $notification->component);
+            $this->assertEquals('assign_notification', $notification->eventtype);
+            $this->assertEquals('https://www.google.com', $notification->contexturl);
+            $this->assertEquals('google', $notification->contexturlname);
+            $this->assertEquals($i, $notification->timecreated);
+
+            if (($i == 1) || ($i == 4)) {
+                $this->assertEquals($timeread, $notification->timeread);
+            } else {
+                $this->assertNull($notification->timeread);
+            }
+
+            $i++;
+        }
+    }
+
+    /**
+     * Creates a legacy message or notification to be used for testing.
+     *
+     * @param int $useridfrom The user id from
+     * @param int $useridto The user id to
+     * @param int $timecreated
+     * @param bool $notification
+     * @param int|null $timeread The time the message/notification was read, null if it hasn't been.
+     * @return int The id of the message (in either the message or message_read table)
+     * @throws dml_exception
+     */
+    private function create_legacy_message_or_notification($useridfrom, $useridto, $timecreated = null,
+            $notification = false, $timeread = null) {
+        global $DB;
+
+        $tabledata = new \stdClass();
+
+        if (is_null($timecreated)) {
+            $timecreated = time();
+        }
+
+        if (!is_null($timeread)) {
+            $table = 'message_read';
+            $tabledata->timeread = $timeread;
+        } else {
+            $table = 'message';
+        }
+
+        if ($notification) {
+            $tabledata->eventtype = 'assign_notification';
+            $tabledata->component = 'mod_assign';
+            $tabledata->notification = 1;
+            $tabledata->contexturl = 'https://www.google.com';
+            $tabledata->contexturlname = 'google';
+        } else {
+            $tabledata->eventtype = 'instantmessage';
+            $tabledata->component = 'moodle';
+            $tabledata->notification = 0;
+        }
+
+        $tabledata->useridfrom = $useridfrom;
+        $tabledata->useridto = $useridto;
+        $tabledata->subject = 'Subject ' . $timecreated;
+        $tabledata->fullmessage = 'Full message ' . $timecreated;
+        $tabledata->fullmessageformat = FORMAT_PLAIN;
+        $tabledata->fullmessagehtml = 'Full message HTML ' . $timecreated;
+        $tabledata->smallmessage = 'Small message ' . $timecreated;
+        $tabledata->timecreated = $timecreated;
+
+        return $DB->insert_record($table, $tabledata);
+    }
+}