diff --git a/src/Controller/Backoffice/QuizController.php b/src/Controller/Backoffice/QuizController.php
index a098dcb..80025ba 100644
--- a/src/Controller/Backoffice/QuizController.php
+++ b/src/Controller/Backoffice/QuizController.php
@@ -156,7 +156,13 @@ class QuizController extends AbstractController
     public function answerMapping(Season $season, Quiz $quiz): Response
     {
         $fetchedQuiz = $this->quizRepository->fetchWithQuestions($quiz->id);
-        \assert($fetchedQuiz->questions->count() > 0);
+
+        if ($fetchedQuiz->questions->isEmpty()) {
+            $this->addFlash(FlashType::Warning, $this->translator->trans('This quiz has no questions yet'));
+
+            return $this->redirectToRoute('tvdt_backoffice_quiz_overview', ['seasonCode' => $season->seasonCode, 'quiz' => $quiz->id]);
+        }
+
         $firstQuestion = $fetchedQuiz->questions->first();
         \assert($firstQuestion instanceof Question);
 
@@ -235,7 +241,7 @@ class QuizController extends AbstractController
 
         $this->em->flush();
 
-        $this->addFlash('success', $this->translator->trans('Candidate answers saved'));
+        $this->addFlash(FlashType::Success, $this->translator->trans('Candidate answers saved'));
 
         return $this->redirectToRoute('tvdt_backoffice_quiz_candidates_question', [
             'seasonCode' => $season->seasonCode,
@@ -357,7 +363,7 @@ class QuizController extends AbstractController
     {
         $this->quizRepository->deleteQuiz($quiz);
 
-        $this->addFlash('success', $this->translator->trans('Quiz deleted'));
+        $this->addFlash(FlashType::Success, $this->translator->trans('Quiz deleted'));
 
         return $this->redirectToRoute('tvdt_backoffice_season', ['seasonCode' => $quiz->season->seasonCode]);
     }
@@ -422,7 +428,7 @@ class QuizController extends AbstractController
 
         $this->em->flush();
 
-        $this->addFlash('success', $this->translator->trans('Candidate status updated'));
+        $this->addFlash(FlashType::Success, $this->translator->trans('Candidate status updated'));
 
         return $this->redirectToRoute('tvdt_backoffice_quiz_candidates_tab', ['seasonCode' => $quiz->season->seasonCode, 'quiz' => $quiz->id]);
     }
diff --git a/src/Repository/QuizRepository.php b/src/Repository/QuizRepository.php
index 893fe6e..43dbf80 100644
--- a/src/Repository/QuizRepository.php
+++ b/src/Repository/QuizRepository.php
@@ -137,8 +137,8 @@ class QuizRepository extends ServiceEntityRepository
     {
         return $this->getEntityManager()->createQuery(<<<dql
             select q, qz, a from Tvdt\Entity\Quiz q
-            join q.questions qz
-            join qz.answers a
+            left join q.questions qz
+            left join qz.answers a
             where q.id = :id
             dql)->setParameter('id', $id)->getSingleResult();
     }
@@ -151,8 +151,8 @@ class QuizRepository extends ServiceEntityRepository
     {
         return $this->getEntityManager()->createQuery(<<<dql
             select q, qz, a, ac, s, sc, qc from Tvdt\Entity\Quiz q
-            join q.questions qz
-            join qz.answers a
+            left join q.questions qz
+            left join qz.answers a
             left join a.candidates ac
             join q.season s
             left join s.candidates sc
diff --git a/tests/Controller/Backoffice/QuizControllerTest.php b/tests/Controller/Backoffice/QuizControllerTest.php
new file mode 100644
index 0000000..0e65754
--- /dev/null
+++ b/tests/Controller/Backoffice/QuizControllerTest.php
@@ -0,0 +1,345 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tvdt\Tests\Controller\Backoffice;
+
+use Doctrine\ORM\EntityManagerInterface;
+use PHPUnit\Framework\Attributes\CoversClass;
+use Safe\DateTimeImmutable;
+use Symfony\Bundle\FrameworkBundle\KernelBrowser;
+use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
+use Symfony\Component\HttpFoundation\Request;
+use Tvdt\Controller\Backoffice\QuizController;
+use Tvdt\Entity\Answer;
+use Tvdt\Entity\Candidate;
+use Tvdt\Entity\GivenAnswer;
+use Tvdt\Entity\Question;
+use Tvdt\Entity\Quiz;
+use Tvdt\Entity\QuizCandidate;
+use Tvdt\Entity\Season;
+use Tvdt\Entity\User;
+
+#[CoversClass(QuizController::class)]
+final class QuizControllerTest extends WebTestCase
+{
+    private KernelBrowser $client;
+
+    private EntityManagerInterface $entityManager;
+
+    protected function setUp(): void
+    {
+        $this->client = self::createClient();
+        $this->entityManager = self::getContainer()->get(EntityManagerInterface::class);
+
+        $user = $this->entityManager->getRepository(User::class)->findOneBy(['email' => 'krtek-admin@example.org']);
+        $this->assertInstanceOf(User::class, $user);
+        $this->client->loginUser($user);
+    }
+
+    private function getQuizByName(string $name): Quiz
+    {
+        $quiz = $this->entityManager->getRepository(Quiz::class)->findOneBy(['name' => $name]);
+        $this->assertInstanceOf(Quiz::class, $quiz);
+
+        return $quiz;
+    }
+
+    private function getCandidate(string $name): Candidate
+    {
+        $candidate = $this->entityManager->getRepository(Candidate::class)->findOneBy(['name' => $name]);
+        $this->assertInstanceOf(Candidate::class, $candidate);
+
+        return $candidate;
+    }
+
+    private function getCsrfTokenFromOverview(Quiz $quiz, string $formActionContains): string
+    {
+        $crawler = $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/overview', $quiz->id));
+        self::assertResponseIsSuccessful();
+
+        $input = $crawler->filter(\sprintf('form[action*="%s"] input[name="_token"]', $formActionContains));
+        $this->assertGreaterThan(0, $input->count(), \sprintf('No form found with action containing "%s"', $formActionContains));
+
+        return (string) $input->first()->attr('value');
+    }
+
+    public function testIndexRedirectsToOverview(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s', $quiz->id));
+
+        self::assertResponseRedirects(\sprintf('/backoffice/season/krtek/quiz/%s/overview', $quiz->id));
+    }
+
+    public function testOverviewLoadsSuccessfully(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/overview', $quiz->id));
+
+        self::assertResponseIsSuccessful();
+        self::assertSelectorTextContains('body', 'Quiz 1');
+    }
+
+    public function testResultTabLoadsSuccessfully(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/result', $quiz->id));
+
+        self::assertResponseIsSuccessful();
+    }
+
+    public function testCandidatesTabLoadsSuccessfully(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/candidates-list', $quiz->id));
+
+        self::assertResponseIsSuccessful();
+    }
+
+    public function testAnswerMappingRedirectsToFirstQuestion(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/answer-mapping', $quiz->id));
+
+        self::assertResponseRedirects();
+        $this->assertStringContainsString('/candidates/', (string) $this->client->getResponse()->headers->get('Location'));
+    }
+
+    public function testCandidatesQuestionTabLoadsSuccessfully(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+        $question = $quiz->questions->first();
+        $this->assertInstanceOf(Question::class, $question);
+
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/candidates/%s', $quiz->id, $question->id));
+
+        self::assertResponseIsSuccessful();
+    }
+
+    public function testSaveCandidateAnswersPersistsSelection(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+        $question = $quiz->questions->first();
+        $this->assertInstanceOf(Question::class, $question);
+        $answer = $question->answers->first();
+        $this->assertInstanceOf(Answer::class, $answer);
+        $candidate = $this->getCandidate('Tom');
+
+        $url = \sprintf('/backoffice/season/krtek/quiz/%s/candidates/%s', $quiz->id, $question->id);
+        $crawler = $this->client->request(Request::METHOD_GET, $url);
+        self::assertResponseIsSuccessful();
+        $token = (string) $crawler->filter('input[name="_token"]')->first()->attr('value');
+
+        $this->client->request(Request::METHOD_POST, $url, [
+            '_token' => $token,
+            'candidate_answer' => [
+                (string) $candidate->id => [(string) $answer->id],
+            ],
+        ]);
+
+        $this->assertResponseRedirects($url);
+        $this->entityManager->clear();
+
+        $savedAnswer = $this->entityManager->getRepository(Answer::class)->find($answer->id);
+        $this->assertInstanceOf(Answer::class, $savedAnswer);
+        $this->assertTrue($savedAnswer->candidates->exists(
+            static fn (int $key, Candidate $c): bool => $c->id->equals($candidate->id),
+        ));
+    }
+
+    public function testToggleCandidateCreatesInactiveQuizCandidate(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+        $candidate = $this->getCandidate('Tom');
+
+        $crawler = $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/candidates-list', $quiz->id));
+        self::assertResponseIsSuccessful();
+        $token = (string) $crawler->filter(\sprintf('form[action*="/%s/toggle"] input[name="_token"]', $candidate->id))->first()->attr('value');
+
+        $this->client->request(Request::METHOD_POST, \sprintf('/backoffice/quiz/%s/candidate/%s/toggle', $quiz->id, $candidate->id), [
+            '_token' => $token,
+        ]);
+
+        self::assertResponseRedirects();
+        $this->entityManager->clear();
+
+        $quizCandidate = $this->entityManager->getRepository(QuizCandidate::class)->findOneBy([
+            'quiz' => $this->getQuizByName('Quiz 1'),
+            'candidate' => $this->getCandidate('Tom'),
+        ]);
+        $this->assertInstanceOf(QuizCandidate::class, $quizCandidate);
+        $this->assertFalse($quizCandidate->active);
+    }
+
+    public function testToggleCandidateTogglesActiveState(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+        $candidate = $this->getCandidate('Tom');
+
+        $quizCandidate = new QuizCandidate($quiz, $candidate);
+        $quizCandidate->active = false;
+
+        $this->entityManager->persist($quizCandidate);
+        $this->entityManager->flush();
+
+        $crawler = $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/candidates-list', $quiz->id));
+        $token = (string) $crawler->filter(\sprintf('form[action*="/%s/toggle"] input[name="_token"]', $candidate->id))->first()->attr('value');
+
+        $this->client->request(Request::METHOD_POST, \sprintf('/backoffice/quiz/%s/candidate/%s/toggle', $quiz->id, $candidate->id), [
+            '_token' => $token,
+        ]);
+
+        self::assertResponseRedirects();
+        $this->entityManager->clear();
+
+        $updated = $this->entityManager->getRepository(QuizCandidate::class)->findOneBy([
+            'quiz' => $this->getQuizByName('Quiz 1'),
+            'candidate' => $this->getCandidate('Tom'),
+        ]);
+        $this->assertInstanceOf(QuizCandidate::class, $updated);
+        $this->assertTrue($updated->active);
+    }
+
+    public function testModifyCorrection(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+        $candidate = $this->getCandidate('Tom');
+
+        // getScores() requires started IS NOT NULL and at least one GivenAnswer
+        $quizCandidate = new QuizCandidate($quiz, $candidate);
+        $quizCandidate->started = new DateTimeImmutable();
+
+        $this->entityManager->persist($quizCandidate);
+        $firstQuestion = $quiz->questions->first();
+        $this->assertInstanceOf(Question::class, $firstQuestion);
+        $answer = $firstQuestion->answers->first();
+        $this->assertInstanceOf(Answer::class, $answer);
+        $this->entityManager->persist(new GivenAnswer($candidate, $quiz, $answer));
+        $this->entityManager->flush();
+
+        $crawler = $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/result', $quiz->id));
+        self::assertResponseIsSuccessful();
+        $token = (string) $crawler->filter(\sprintf('form[action*="%s/modify_correction"] input[name="_token"]', $candidate->id))->first()->attr('value');
+
+        $this->client->request(Request::METHOD_POST, \sprintf('/backoffice/quiz/%s/candidate/%s/modify_correction', $quiz->id, $candidate->id), [
+            '_token' => $token,
+            'corrections' => '1.5',
+        ]);
+
+        self::assertResponseRedirects();
+        $this->entityManager->clear();
+
+        $updated = $this->entityManager->getRepository(QuizCandidate::class)->findOneBy([
+            'quiz' => $this->getQuizByName('Quiz 1'),
+            'candidate' => $this->getCandidate('Tom'),
+        ]);
+        $this->assertInstanceOf(QuizCandidate::class, $updated);
+        $this->assertEqualsWithDelta(1.5, $updated->corrections, \PHP_FLOAT_EPSILON);
+    }
+
+    public function testModifyPenalty(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 1');
+        $candidate = $this->getCandidate('Claudia');
+
+        $quizCandidate = new QuizCandidate($quiz, $candidate);
+        $quizCandidate->started = new DateTimeImmutable();
+
+        $this->entityManager->persist($quizCandidate);
+        $firstQuestion = $quiz->questions->first();
+        $this->assertInstanceOf(Question::class, $firstQuestion);
+        $answer = $firstQuestion->answers->first();
+        $this->assertInstanceOf(Answer::class, $answer);
+        $this->entityManager->persist(new GivenAnswer($candidate, $quiz, $answer));
+        $this->entityManager->flush();
+
+        $crawler = $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/result', $quiz->id));
+        self::assertResponseIsSuccessful();
+        $token = (string) $crawler->filter(\sprintf('form[action*="%s/modify_penalty"] input[name="_token"]', $candidate->id))->first()->attr('value');
+
+        $this->client->request(Request::METHOD_POST, \sprintf('/backoffice/quiz/%s/candidate/%s/modify_penalty', $quiz->id, $candidate->id), [
+            '_token' => $token,
+            'penalty' => '30',
+        ]);
+
+        self::assertResponseRedirects();
+        $this->entityManager->clear();
+
+        $updated = $this->entityManager->getRepository(QuizCandidate::class)->findOneBy([
+            'quiz' => $this->getQuizByName('Quiz 1'),
+            'candidate' => $this->getCandidate('Claudia'),
+        ]);
+        $this->assertInstanceOf(QuizCandidate::class, $updated);
+        $this->assertSame(30, $updated->penaltySeconds);
+    }
+
+    public function testDeleteQuiz(): void
+    {
+        $quiz = $this->getQuizByName('Quiz 2');
+        $quizId = $quiz->id;
+        $token = $this->getCsrfTokenFromOverview($quiz, '/delete');
+
+        $this->client->request(Request::METHOD_POST, \sprintf('/backoffice/quiz/%s/delete', $quiz->id), [
+            '_token' => $token,
+        ]);
+
+        self::assertResponseRedirects('/backoffice/season/krtek');
+        $this->entityManager->clear();
+        $this->assertNotInstanceOf(Quiz::class, $this->entityManager->getRepository(Quiz::class)->find($quizId));
+    }
+
+    public function testNonOwnerIsDenied(): void
+    {
+        $user = $this->entityManager->getRepository(User::class)->findOneBy(['email' => 'test@example.org']);
+        $this->assertInstanceOf(User::class, $user);
+        $this->client->loginUser($user);
+
+        $quiz = $this->getQuizByName('Quiz 1');
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/overview', $quiz->id));
+
+        self::assertResponseStatusCodeSame(403);
+    }
+
+    public function testOverviewLoadsForEmptyQuiz(): void
+    {
+        $season = $this->entityManager->getRepository(Season::class)->findOneBy(['seasonCode' => 'krtek']);
+        $this->assertInstanceOf(Season::class, $season);
+
+        $emptyQuiz = new Quiz();
+        $emptyQuiz->name = 'Empty Quiz';
+
+        $season->addQuiz($emptyQuiz);
+        $this->entityManager->persist($emptyQuiz);
+        $this->entityManager->flush();
+
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/overview', $emptyQuiz->id));
+
+        self::assertResponseIsSuccessful();
+        self::assertSelectorTextContains('body', 'Empty Quiz');
+    }
+
+    public function testAnswerMappingRedirectsWithFlashWhenNoQuestions(): void
+    {
+        $season = $this->entityManager->getRepository(Season::class)->findOneBy(['seasonCode' => 'krtek']);
+        $this->assertInstanceOf(Season::class, $season);
+
+        $emptyQuiz = new Quiz();
+        $emptyQuiz->name = 'Empty Quiz';
+
+        $season->addQuiz($emptyQuiz);
+        $this->entityManager->persist($emptyQuiz);
+        $this->entityManager->flush();
+
+        $this->client->request(Request::METHOD_GET, \sprintf('/backoffice/season/krtek/quiz/%s/answer-mapping', $emptyQuiz->id));
+
+        self::assertResponseRedirects(\sprintf('/backoffice/season/krtek/quiz/%s/overview', $emptyQuiz->id));
+        $this->client->followRedirect();
+        self::assertSelectorTextContains('body', 'Deze test heeft nog geen vragen');
+    }
+}
diff --git a/translations/messages+intl-icu.nl.xliff b/translations/messages+intl-icu.nl.xliff
index 5f299a4..90b8cb2 100644
--- a/translations/messages+intl-icu.nl.xliff
+++ b/translations/messages+intl-icu.nl.xliff
@@ -621,6 +621,10 @@
         <source>This quiz has already been filled in and can no longer be altered</source>
         <target>Deze quiz is al ingevuld en kan niet meer worden gewijzigd</target>
       </trans-unit>
+      <trans-unit id="Xq9rT2p" resname="This quiz has no questions yet">
+        <source>This quiz has no questions yet</source>
+        <target>Deze test heeft nog geen vragen</target>
+      </trans-unit>
       <trans-unit id="Dptvysv" resname="Time">
         <source>Time</source>
         <target>Tijd</target>