/**
  * Test view_page.
  */
 public function test_view_page()
 {
     // Test invalid page id.
     try {
         mod_wiki_external::view_page(0);
         $this->fail('Exception expected due to invalid view_page page id.');
     } catch (moodle_exception $e) {
         $this->assertEquals('incorrectpageid', $e->errorcode);
     }
     // Test not-enrolled user.
     $usernotenrolled = self::getDataGenerator()->create_user();
     $this->setUser($usernotenrolled);
     try {
         mod_wiki_external::view_page($this->firstpage->id);
         $this->fail('Exception expected due to not enrolled user.');
     } catch (moodle_exception $e) {
         $this->assertEquals('requireloginerror', $e->errorcode);
     }
     // Test user with full capabilities.
     $this->setUser($this->student);
     // Trigger and capture the event.
     $sink = $this->redirectEvents();
     $result = mod_wiki_external::view_page($this->firstpage->id);
     $result = external_api::clean_returnvalue(mod_wiki_external::view_page_returns(), $result);
     $events = $sink->get_events();
     $this->assertCount(1, $events);
     $event = array_shift($events);
     // Checking that the event contains the expected values.
     $this->assertInstanceOf('\\mod_wiki\\event\\page_viewed', $event);
     $this->assertEquals($this->context, $event->get_context());
     $pageurl = new \moodle_url('/mod/wiki/view.php', array('pageid' => $this->firstpage->id));
     $this->assertEquals($pageurl, $event->get_url());
     $this->assertEventContextNotUsed($event);
     $this->assertNotEmpty($event->get_name());
     // Test user with no capabilities.
     // We need a explicit prohibit since this capability is allowed for students by default.
     assign_capability('mod/wiki:viewpage', CAP_PROHIBIT, $this->studentrole->id, $this->context->id);
     accesslib_clear_all_caches_for_unit_testing();
     try {
         mod_wiki_external::view_page($this->firstpage->id);
         $this->fail('Exception expected due to missing capability.');
     } catch (moodle_exception $e) {
         $this->assertEquals('cannotviewpage', $e->errorcode);
     }
 }