Validate against empty form submission for find_users_by_email

This included:
- creating a new form SearchUsersByEmailForm with validation
on its search field

- introducing 400 status to the view  if the form does not validate

- fixing the POST request data structure in the tests (it was
incorrect before and uncaught due to lack of validation and mocking
the response from the API.

app/main/forms.py

@@ -853,6 +853,15 @@ class SearchTemplatesForm(StripWhitespaceForm):
     search = SearchField('Search by name')
 
 
+class SearchUsersByEmailForm(StripWhitespaceForm):
+
+    search = SearchField('Search by name or email address',
+        validators=[
+            DataRequired("You need to enter full or partial e-mail address to search by.")
+        ]
+    )
+
+
 class SearchUsersForm(StripWhitespaceForm):
 
     search = SearchField('Search by name or email address')

app/main/views/find_users.py

@@ -4,19 +4,22 @@ from flask_login import login_required
 from app import user_api_client
 from app.main import main
 from app.utils import user_is_platform_admin
-from app.main.forms import SearchUsersForm
+from app.main.forms import SearchUsersByEmailForm
 
 
 @main.route("/find-users-by-email", methods=['GET', 'POST'])
 @login_required
 @user_is_platform_admin
 def find_users_by_email():
-    form = SearchUsersForm()
+    form = SearchUsersByEmailForm()
     users_found = None
+    status = 200
     if form.validate_on_submit():
         users_found = user_api_client.find_users_by_full_or_partial_email(form.search.data)['data']
+    elif request.method == 'POST':
+        status = 400
     return render_template(
         'views/find-users/find-users-by-email.html',
         form=form,
         users_found=users_found
-    )
+    ), status

tests/app/main/views/test_find_users.py

@@ -30,7 +30,7 @@ def test_find_users_by_email_displays_users_found(
     mock_get_user(mocker, user=platform_admin_user)
     client.login(platform_admin_user)
     mocker.patch('app.user_api_client.find_users_by_full_or_partial_email', return_value={"data": [user_json()]}, autospec=True)
-    response = client.post(url_for('main.find_users_by_email', data=[{"email": "twilight.sparkle"}]))
+    response = client.post(url_for('main.find_users_by_email'), data={"search": "twilight.sparkle"})
     assert response.status_code == 200
 
     document = html.fromstring(response.get_data(as_text=True))
@@ -44,8 +44,22 @@ def test_find_users_by_email_displays_message_if_no_users_found(
     mock_get_user(mocker, user=platform_admin_user)
     client.login(platform_admin_user)
     mocker.patch('app.user_api_client.find_users_by_full_or_partial_email', return_value={"data": []}, autospec=True)
-    response = client.post(url_for('main.find_users_by_email', data=[{"email": "twilight.sparkle"}]))
+    response = client.post(url_for('main.find_users_by_email'), data={"search": "twilight.sparkle"})
     assert response.status_code == 200
 
     document = html.fromstring(response.get_data(as_text=True))
     assert "No users found." in document.text_content()
+
+
+def test_find_users_by_email_validates_against_empty_search_submission(
+        client,
+        platform_admin_user,
+        mocker
+):
+    mock_get_user(mocker, user=platform_admin_user)
+    client.login(platform_admin_user)
+    response = client.post(url_for('main.find_users_by_email'), data={"search": ""})
+    assert response.status_code == 400
+
+    document = html.fromstring(response.get_data(as_text=True))
+    assert "You need to enter full or partial e-mail address to search by." in document.text_content()