diff --git a/lib.php b/lib.php
index efc09a2..24466f1 100644
--- a/lib.php
+++ b/lib.php
@@ -191,13 +191,10 @@ function kialo_update_visibility_depending_on_accepted_terms(): void {
  * @param stdClass $grades grade object
  * @return int Returns GRADE_UPDATE_OK, GRADE_UPDATE_FAILED, GRADE_UPDATE_MULTIPLE or GRADE_UPDATE_ITEM_LOCKED
  */
-function kialo_grade_item_update(stdClass $kialo, $grades = null): int {
+function kialo_grade_item_update(stdClass $kialo, ?stdClass $grades = null): int {
     $params = [
         'itemname' => $kialo->name,
         'idnumber' => $kialo->cmidnumber ?? '',
-        'itemtype' => 'mod',
-        'itemmodule' => 'kialo',
-        'itemnumber' => 0,
     ];
 
     if ($kialo->grade > 0) {
@@ -241,9 +238,7 @@ function kialo_update_grades(stdClass $kialo, int $userid = 0, bool $nullifnone
     global $CFG, $DB;
     require_once($CFG->libdir.'/gradelib.php');
 
-    if (empty($kialo->assessed) || !$kialo->assessed) {
-        kialo_grade_item_update($kialo);
-    } else if ($grades = kialo_get_user_grades($kialo, $userid)) {
+    if ($userid > 0 && $grades = kialo_get_user_grades($kialo, $userid)) {
         kialo_grade_item_update($kialo, $grades);
     } else if ($userid && $nullifnone) {
         $grade = new stdClass();
diff --git a/tests/classes/kialo_config_test.php b/tests/classes/kialo_config_test.php
index 698e352..51018c8 100644
--- a/tests/classes/kialo_config_test.php
+++ b/tests/classes/kialo_config_test.php
@@ -86,6 +86,7 @@ public function test_get_platform(): void {
 
         $this->assertEquals("https://www.example.com/moodle/mod/kialo", $platform->getAudience());
         $this->assertEquals("https://www.example.com/moodle/mod/kialo/lti_auth.php", $platform->getOidcAuthenticationUrl());
+        $this->assertEquals("https://www.example.com/moodle/mod/kialo/lti_token.php", $platform->getOAuth2AccessTokenUrl());
         $this->assertEquals("kialo-moodle-plugin", $platform->getIdentifier());
         $this->assertEquals("Kialo Moodle Plugin", $platform->getName());
     }
@@ -125,4 +126,19 @@ public function test_registration(): void {
         $this->assertEquals("https://www.kialo-edu.com/lti/jwks.json", $registration->getToolJwksUrl());
         $this->assertEquals("https://www.example.com/moodle/mod/kialo/lti_jwks.php", $registration->getPlatformJwksUrl());
     }
+
+    /**
+     * Tests the registration repository.
+     * @covers \mod_kialo\kialo_config::get_instance::get_registration_repository
+     */
+    public function test_registration_repository(): void {
+        $repo = kialo_config::get_instance()->get_registration_repository("DEPLID1234");
+        $this->assertNotNull($repo);
+
+        $this->assertNull($repo->find("NONEXISTENT"));
+
+        $registration = $repo->find("kialo-moodle-registration");
+        $this->assertNotNull($registration);
+        $this->assertEquals("kialo-moodle-registration", $registration->getIdentifier());
+    }
 }
diff --git a/tests/classes/kialo_view_test.php b/tests/classes/kialo_view_test.php
index cec8a2c..264da6e 100644
--- a/tests/classes/kialo_view_test.php
+++ b/tests/classes/kialo_view_test.php
@@ -25,6 +25,7 @@
 
 namespace mod_kialo;
 
+use GuzzleHttp\Psr7\Response;
 use stdClass;
 
 defined('MOODLE_INTERNAL') || die();
@@ -224,4 +225,38 @@ public function test_group_info_grouping(): void {
         $this->assertEquals("grouping-{$grouping->id}", $groupinfo->groupid);
         $this->assertEquals($grouping->name, $groupinfo->groupname);
     }
+
+    /**
+     * Tests writing an HTTP response.
+     *
+     * @return void
+     * @covers \mod_kialo\kialo_view::write_response
+     */
+    public function test_write_response(): void {
+        $headers = [
+            'Content-Type' => 'application/json',
+            'X-Test-Header' => 'test',
+        ];
+        $json = json_encode(['message' => 'Hello, world!']);
+        $response = new Response(200, $headers, $json);
+
+        ob_start();
+        kialo_view::write_response($response);
+        $output = ob_get_clean();
+
+        $this->assertStringContainsString('HTTP/1.1 200 OK', $output);
+        $this->assertStringContainsString('Content-Type: application/json', $output);
+        $this->assertStringContainsString('X-Test-Header: test', $output);
+        $this->assertStringContainsString($json, $output);
+    }
+}
+
+/**
+ * Mocks the header function, simpling printing to stdout so it can be asserted.
+ *
+ * @param string $str
+ * @return void
+ */
+function header(string $str): void {
+    echo $str . '\n';
 }
diff --git a/tests/classes/moodle_cache_test.php b/tests/classes/moodle_cache_test.php
index 1e0aeda..632456b 100644
--- a/tests/classes/moodle_cache_test.php
+++ b/tests/classes/moodle_cache_test.php
@@ -53,6 +53,17 @@ protected function setUp(): void {
         $this->cache = moodle_cache::nonce_cache();
     }
 
+    /**
+     * Tests that the nonce cache is created correctly.
+     *
+     * @return void
+     * @covers \mod_kialo\moodle_cache::nonce_cache
+     */
+    public function test_access_token_cache(): void {
+        $this->cache = moodle_cache::access_token_cache();
+        $this->assertInstanceOf(moodle_cache::class, $this->cache);
+    }
+
     /**
      * Tests that setting and getting of individual cache items works.
      *
diff --git a/tests/lib_test.php b/tests/lib_test.php
index 448314d..abb5345 100644
--- a/tests/lib_test.php
+++ b/tests/lib_test.php
@@ -71,14 +71,24 @@ public function test_kialo_supports(): void {
      * Check add instance
      *
      * @covers ::kialo_add_instance
+     * @var $DB \DB
      */
     public function test_kialo_add_instance(): void {
+        global $DB;
         $this->resetAfterTest();
 
         $course = $this->getDataGenerator()->create_course();
         $id = kialo_add_instance((object) ["name" => "Test", "course" => $course->id, "grade" => 100]);
 
         $this->assertNotNull($id);
+
+        // By default, the activity is created with a maximum grade of 100 points.
+        $instance = $DB->get_record('kialo', ['id' => $id], '*', MUST_EXIST);
+        $this->assertEquals(100, $instance->grade);
+
+        // A line item should be created in the gradebook.
+        $gradeitem = $DB->get_record('grade_items', ['iteminstance' => $id, 'itemmodule' => 'kialo'], '*', MUST_EXIST);
+        $this->assertEquals(100, $gradeitem->grademax);
     }
 
     /**
@@ -216,4 +226,106 @@ public function test_disable_module_when_terms_have_not_been_accepted(): void {
 
         $this->assertNotContains('kialo', \core_plugin_manager::instance()->get_enabled_plugins('mod'));
     }
+
+    /**
+     * Check the kialo_grade_item_update function.
+     *
+     * @covers ::kialo_grade_item_update
+     * @var $DB \DB
+     */
+    public function test_kialo_grade_item_update_no_scale(): void {
+        global $DB;
+        $this->resetAfterTest();
+
+        $course = $this->getDataGenerator()->create_course();
+        $kialo = $this->getDataGenerator()->create_module('kialo', ['course' => $course]);
+
+        $this->assertEquals(GRADE_UPDATE_OK, kialo_grade_item_update($kialo));
+
+        // Line item should have been updated/created accordingly.
+        $gradeitem = $DB->get_record('grade_items', ['iteminstance' => $kialo->id, 'itemmodule' => 'kialo'], '*', MUST_EXIST);
+        $this->assertEquals(100, $gradeitem->grademax);
+        $this->assertEquals(0, $gradeitem->grademin);
+        $this->assertEquals(GRADE_TYPE_VALUE, $gradeitem->gradetype);
+    }
+
+    /**
+     * Check the kialo_grade_item_update function when using scales instead of regular points.
+     *
+     * @covers ::kialo_grade_item_update
+     * @var $DB \DB
+     */
+    public function test_kialo_grade_item_update_scale(): void {
+        global $DB;
+        $this->resetAfterTest();
+
+        $course = $this->getDataGenerator()->create_course();
+        $kialo = $this->getDataGenerator()->create_module('kialo', ['course' => $course]);
+        $kialo->grade = -1;
+
+        $this->assertEquals(GRADE_UPDATE_OK, kialo_grade_item_update($kialo));
+
+        // Line item should have been updated/created accordingly.
+        $gradeitem = $DB->get_record('grade_items', ['iteminstance' => $kialo->id, 'itemmodule' => 'kialo'], '*', MUST_EXIST);
+        $this->assertEquals(1, $gradeitem->scaleid); // The value of `-grade` is the scale ID.
+        $this->assertEquals(GRADE_TYPE_SCALE, $gradeitem->gradetype);
+    }
+
+    /**
+     * Check that updating and reading grades works.
+     *
+     * @covers ::kialo_grade_item_update
+     * @covers ::kialo_get_user_grades
+     * @var $DB \DB
+     */
+    public function test_kialo_get_and_set_user_grades(): void {
+        global $DB;
+        $this->resetAfterTest();
+
+        $course = $this->getDataGenerator()->create_course();
+        $user = $this->getDataGenerator()->create_user();
+        $kialo = $this->getDataGenerator()->create_module('kialo', ['course' => $course]);
+
+        // Initially there should be no grade.
+        $grades = kialo_get_user_grades($kialo, $user->id);
+        $this->assertEmpty($grades->errors);
+        $this->assertCount(1, $grades->items);
+
+        $gradeitem = $grades->items[0];
+        $this->assertEquals(0, $gradeitem->grademin);
+        $this->assertEquals(100, $gradeitem->grademax);
+        $this->assertEquals('mod', $gradeitem->itemtype);
+        $this->assertEquals('kialo', $gradeitem->itemmodule);
+        $this->assertEquals(0, $gradeitem->itemnumber);
+        $this->assertEquals(0, $gradeitem->scaleid);
+
+        $this->assertCount(1, $gradeitem->grades);
+        $grade = current($gradeitem->grades);
+        $this->assertNull($grade->grade);
+        $this->assertNull($grade->feedback);
+        $this->assertNull($grade->datesubmitted);
+
+        // Set a grade.
+        $grade = new \stdClass();
+        $grade->userid = $user->id;
+        $grade->rawgrade = 50;
+        $grade->feedback = 'Good job!';
+        $grade->datesubmitted = time();
+        kialo_grade_item_update($kialo, $grade);
+
+        // The grade should be set now.
+        $grades = kialo_get_user_grades($kialo, $user->id);
+        $this->assertEmpty($grades->errors);
+        $this->assertCount(1, $grades->items);
+
+        $gradeitem = $grades->items[0];
+        $this->assertCount(1, $gradeitem->grades);
+        $grade = current($gradeitem->grades);
+        $this->assertEquals(50, $grade->grade);
+        $this->assertEquals('Good job!', $grade->feedback);
+        $this->assertNotNull($grade->datesubmitted);
+
+        // I don't know why these warnings appear. The test itself works as expected, and the plugin code itself, as well.
+        $this->expectOutputRegex('/(The instance of this module does not exist)+/');
+    }
 }