Simple flask test.

tests/conftest.py

+import pytest
+from flask import Flask
+
+from tjts5901.app import create_app
+
+
+@pytest.fixture
+def app():
+    """
+    Application fixture.
+
+    Every test that requires `app` as parameter can use this fixture.
+
+    Example:
+    >>> def test_mytest(app: Flask):
+    >>>     ...
+    """
+    _app = create_app({
+        'TESTING': True,
+        'DEBUG': False,
+
+        # We need to set SERVER_NAME and PREFERRED_URL_SCHEME for testing.
+        'SERVER_NAME': 'localhost',
+        'PREFERRED_URL_SCHEME': 'http',
+    })
+
+    # If you have done ties4080 course and have used Flask-WTF, you might
+    # have noticed that CSRF protection is enabled by default. This is
+    # problematic for testing, because we don't have a browser to generate
+    # CSRF tokens. We can disable CSRF protection for testing, but we need
+    # to make sure that we don't have CSRF protection enabled in production.
+
+    # _app.config['WTF_CSRF_ENABLED'] = False
+    # _app.config['WTF_CSRF_METHODS'] = []
+    # _app.config['WTF_CSRF_CHECK_DEFAULT'] = False
+
+    _app.testing = True
+    yield _app
+
+    # Do some cleanup here if needed.
+    ...
+
+
+@pytest.fixture
+def client(app: Flask):
+    """
+    Setup testing client.
+
+    See:
+    https://flask.palletsprojects.com/en/2.2.x/testing/#the-testing-skeleton
+    https://werkzeug.palletsprojects.com/en/2.2.x/test/#werkzeug.test.Client
+    """
+
+    # Setup all the context needed for client to work.
+    with app.test_client() as test_client:
+        with app.app_context():
+            yield test_client
+
+

tests/test_app.py

+"""
+Flask based tests
+=================
+
+Uses the flask testclient to retrieve and post pages in application.
+"""
+
+from flask.testing import FlaskClient
+
+# This is the string we are looking for in the frontpage.
+IN_TITLE = "TJTS5901"
+
+
+def test_fetch_mainpage(client: FlaskClient):
+    """
+    Fetch frontpage and check that it has <title>.
+
+    :param client: Flask test client. See conftest.py for more info how it is
+        created.
+    """
+
+    # Request frontpage
+    page = client.get('/')
+
+    # Check that page contains something.
+    # Note about assert; assert is special kind of keyword. By default
+    # assert statements are run, but if they are deemed too costly, python
+    # interepter can be defined to pass them with `python -O` flag.
+    # If assert statement return False, new assert exception is raised, and
+    # and test is deemed to fail. After first statement - condition - human
+    # readable reason for failure can be provided.
+    # >>> assert (condition-for-failure, "human readable reason")
+    assert page, "Did not get anything"
+    assert IN_TITLE.encode() in page.data, f"Page didn't have {IN_TITLE}"