Add test for database cascades

tests/test_database.py

 import pytest
 from flask import Flask
 
-from zesje.database import db, Exam, _generate_exam_token
+from zesje.database import db, _generate_exam_token, Exam, Problem, ProblemWidget, Solution
+from zesje.database import Submission, Scan, Page, ExamWidget, FeedbackOption
 
 
 @pytest.mark.parametrize('duplicate_count', [
@@ -32,3 +33,141 @@ def test_exam_generate_token_length_uppercase(duplicate_count, monkeypatch):
         id = _generate_exam_token()
         assert len(id) == 12
         assert id.isupper()
+
+
+def test_cascades_exam(empty_app, exam, problem, submission, scan, exam_widget):
+    """Tests the cascades defined for a exam
+
+    Tests the cascades for the following relations:
+    - Exam -> Submission
+    - Exam -> Problem
+    - Exam -> Scan
+    - Exam -> ExamWidget
+    """
+    empty_app.app_context().push()
+    exam.problems = [problem]
+    exam.scans = [scan]
+    exam.submissions = [submission]
+    exam.widgets = [exam_widget]
+
+    db.session.add(exam)
+    db.session.commit()
+
+    assert problem in db.session
+    assert submission in db.session
+    assert scan in db.session
+    assert exam_widget in db.session
+
+    db.session.delete(exam)
+    db.session.commit()
+
+    assert problem not in db.session
+    assert submission not in db.session
+    assert scan not in db.session
+    assert exam_widget not in db.session
+
+
+def test_cascades_problem(empty_app, exam, problem, submission, solution, problem_widget, feedback_option):
+    """Tests the cascades defined for a problem
+
+    Tests the cascades for the following relations:
+    - Problem -> Solution
+    - Problem -> ProblemWidget
+    - Problem -> FeedbackOption
+    """
+    empty_app.app_context().push()
+
+    exam.problems = [problem]
+    exam.submissions = [submission]
+    solution.submission = submission
+    problem.widget = problem_widget
+    problem.solutions = [solution]
+    problem.feedback_options = [feedback_option]
+
+    db.session.add_all([exam, problem, submission])
+    db.session.commit()
+
+    assert solution in db.session
+    assert problem_widget in db.session
+    assert feedback_option in db.session
+
+    db.session.delete(problem)
+    db.session.commit()
+
+    assert solution not in db.session
+    assert problem_widget not in db.session
+    assert feedback_option not in db.session
+
+
+def test_cascades_submission(empty_app, exam, problem, submission, solution, page):
+    """Tests the cascades defined for a submission
+
+    Tests the cascades for the following relations:
+    - Submission -> Solution
+    - Submission -> Page
+    """
+    empty_app.app_context().push()
+
+    exam.problems = [problem]
+    exam.submissions = [submission]
+
+    solution.problem = problem
+    solution.submission = submission
+    page.submission = submission
+
+    db.session.add_all([exam, problem, submission])
+    db.session.commit()
+
+    assert solution in db.session
+    assert page in db.session
+
+    db.session.delete(submission)
+    db.session.commit()
+
+    assert solution not in db.session
+    assert page not in db.session
+
+
+@pytest.fixture
+def exam():
+    return Exam(name='')
+
+
+@pytest.fixture
+def problem():
+    return Problem(name='')
+
+
+@pytest.fixture
+def problem_widget():
+    return ProblemWidget(name='', page=0, x=0, y=0, width=0, height=0)
+
+
+@pytest.fixture
+def exam_widget():
+    return ExamWidget(name='', x=0, y=0)
+
+
+@pytest.fixture
+def submission():
+    return Submission(copy_number=0)
+
+
+@pytest.fixture
+def solution():
+    return Solution()
+
+
+@pytest.fixture
+def scan():
+    return Scan(name='', status='')
+
+
+@pytest.fixture
+def page():
+    return Page(path='', number=0)
+
+
+@pytest.fixture
+def feedback_option():
+    return FeedbackOption(text='')