diff --git a/lib/classes/task/completion_daily_task.php b/lib/classes/task/completion_daily_task.php
index 2457200d3ad..b7966bfd6a5 100644
--- a/lib/classes/task/completion_daily_task.php
+++ b/lib/classes/task/completion_daily_task.php
@@ -71,7 +71,8 @@ class completion_daily_task extends scheduled_task {
                 INNER JOIN {user_enrolments} ue ON ue.userid = u.id
                 INNER JOIN {enrol} e ON e.id = ue.enrolid
                 INNER JOIN {course} c ON c.id = e.courseid
-                INNER JOIN {role_assignments} ra ON ra.userid = u.id
+                INNER JOIN {context} con ON con.contextlevel = ? AND con.instanceid = c.id
+                INNER JOIN {role_assignments} ra ON ra.userid = u.id AND ra.contextid = con.id
                  LEFT JOIN {course_completions} crc ON crc.course = c.id AND crc.userid = u.id
                      WHERE c.enablecompletion = 1
                        AND crc.timeenrolled IS NULL
@@ -83,7 +84,7 @@ class completion_daily_task extends scheduled_task {
                        $sqlroles
                   ORDER BY course, userid";
             $now = time();
-            $rs = $DB->get_recordset_sql($sql, [$now, $now, $now, $now]);
+            $rs = $DB->get_recordset_sql($sql, [CONTEXT_COURSE, $now, $now]);
 
             // Check if result is empty.
             if (!$rs->valid()) {
diff --git a/lib/tests/completion_daily_task_test.php b/lib/tests/completion_daily_task_test.php
new file mode 100644
index 00000000000..e694ac06604
--- /dev/null
+++ b/lib/tests/completion_daily_task_test.php
@@ -0,0 +1,123 @@
+<?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/>.
+
+/**
+ * Contains the class containing unit tests for the daily completion cron task.
+ *
+ * @package   core
+ * @copyright 2020 Jun Pataleta
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core\task;
+
+use advanced_testcase;
+
+/**
+ * Class containing unit tests for the daily completion cron task.
+ *
+ * @package core
+ * @copyright 2020 Jun Pataleta
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class core_completion_cron_task_testcase extends advanced_testcase {
+
+    /**
+     * Test calendar cron task with a broken subscription URL.
+     */
+    public function test_completion_daily_cron() {
+        global $DB;
+
+        $this->resetAfterTest();
+
+        set_config('enablecompletion', 1);
+        set_config('enrol_plugins_enabled', 'self,manual');
+
+        $generator = $this->getDataGenerator();
+
+        $now = time();
+        $lastweek = $now - WEEKSECS;
+        $yesterday = $now - DAYSECS;
+        $tomorrow = $now + DAYSECS;
+
+        // Course with completion enabled and has already started.
+        $c1 = $generator->create_course(['enablecompletion' => 1, 'startdate' => $lastweek]);
+        // Course with completion enabled but hasn't started yet.
+        $c2 = $generator->create_course(['enablecompletion' => 1, 'startdate' => $tomorrow]);
+        // Completion not enabled.
+        $c3 = $generator->create_course();
+
+        // Create users.
+        $t1 = $generator->create_user(['username' => 't1']);
+        $t2 = $generator->create_user(['username' => 't2']);
+        $s1 = $generator->create_user(['username' => 's1']);
+        $s2 = $generator->create_user(['username' => 's2']);
+
+        // Enrol s1 by self and manual methods to c1.
+        $generator->enrol_user($s1->id, $c1->id, 'student', 'self', $lastweek);
+        $generator->enrol_user($s1->id, $c1->id, 'student', 'manual', $yesterday);
+
+        // Enrol s1 by self and manual methods to c2.
+        $generator->enrol_user($s1->id, $c2->id, 'student', 'self');
+        $generator->enrol_user($s1->id, $c2->id, 'student', 'manual', $tomorrow);
+
+        // Enrol s1 by self and manual methods to c3.
+        $generator->enrol_user($s1->id, $c3->id, 'student', 'self', $lastweek);
+        $generator->enrol_user($s1->id, $c3->id, 'student');
+
+        // Enrol the rest.
+        foreach ([$c1, $c2, $c3] as $course) {
+            // Enrol s2 by manual and self enrol methods.
+            $generator->enrol_user($s2->id, $course->id, 'student', 'self');
+            $generator->enrol_user($s2->id, $course->id, 'student', 'manual', $course->startdate);
+
+            // Enrol t1 as teacher to these courses.
+            $generator->enrol_user($t1->id, $course->id, 'editingteacher', 'manual', $course->startdate);
+            $generator->enrol_user($t1->id, $course->id, 'editingteacher', 'manual', $course->startdate);
+
+            // Enrol t2 as a non-editing teacher to these courses.
+            $generator->enrol_user($t1->id, $course->id, 'teacher', 'manual', $course->startdate);
+            $generator->enrol_user($t1->id, $course->id, 'teacher', 'manual', $course->startdate);
+        }
+
+        // The course completion table should be empty prior to running the task.
+        $this->assertEquals(0, $DB->count_records('course_completions'));
+
+        // Run the daily completion task.
+        ob_start();
+        $task = new completion_daily_task();
+        $task->execute();
+        ob_end_clean();
+
+        // Confirm there are no completion records for teachers nor for courses that haven't started yet or without completion.
+        list($tsql, $tparams) = $DB->get_in_or_equal([$t1->id, $t2->id], SQL_PARAMS_NAMED);
+        list($csql, $cparams) = $DB->get_in_or_equal([$c2->id, $c3->id], SQL_PARAMS_NAMED);
+        $select = "userid $tsql OR course $csql";
+        $params = array_merge($tparams, $cparams);
+        $this->assertEmpty($DB->get_records_select('course_completions', $select, $params));
+
+        // We should have 2 completion records for both s1 and s2 in course c1.
+        $this->assertCount(2, $DB->get_records('course_completions'));
+
+        // Get s1's completion record from c1.
+        $s1c1 = $DB->get_record('course_completions', ['userid' => $s1->id, 'course' => $c1->id]);
+        $this->assertEquals(userdate($now), userdate($s1c1->timeenrolled));
+
+        // Get s2's completion record from c1.
+        $s2c1 = $DB->get_record('course_completions', ['userid' => $s2->id, 'course' => $c1->id]);
+        $this->assertEquals(userdate($now), userdate($s2c1->timeenrolled));
+    }
+}