diff --git a/server/books/schema/mutations/utils.py b/server/books/schema/mutations/utils.py
index 26d0df40..20e87a1d 100644
--- a/server/books/schema/mutations/utils.py
+++ b/server/books/schema/mutations/utils.py
@@ -1,15 +1,7 @@
-# -*- coding: utf-8 -*-
-#
-# Iterativ GmbH
-# http://www.iterativ.ch/
-#
-# Copyright (c) 2018 Iterativ GmbH. All rights reserved.
-#
-# Created on 25.09.18
-# @author: Ramon Wenger <ramon.wenger@iterativ.ch>
-
 import bleach
 import re
+import uuid
+
 
 from typing import List, Union
 
@@ -33,35 +25,45 @@ def get_previous_item(previous_contents: Union[StreamValue, List[dict]], item: d
         contents = previous_contents.raw_data
     else:
         contents = previous_contents
-    return next((c for c in contents if c.get('id', None) == item['id']), None)
+    return next((c for c in contents if c.get("id", None) == item["id"]), None)
 
 
 def handle_text(text):
-    is_list = bool(re.search(r'<ul>', text))
+    is_list = bool(re.search(r"<ul>", text))
     if is_list:
         # let's assume this is formatted correctly already, otherwise bleach or the browser should strip / ignore it
         return text
     else:
-        parts = re.split(r'[\r\n]+', text)
-        paragraphs = ['<p>{}</p>'.format(p.strip()) for p in parts]
-        return '\n'.join(paragraphs)
+        parts = re.split(r"[\r\n]+", text)
+        paragraphs = ["<p>{}</p>".format(p.strip()) for p in parts]
+        return "\n".join(paragraphs)
 
 
 ALLOWED_BLOCKS = (
-    'text_block',
-    'student_entry',
-    'image_url_block',
-    'link_block',
-    'video_block',
-    'assignment',
-    'document_block',
-    'content_list_item',
-    'subtitle',
-    'readonly'
+    "text_block",
+    "student_entry",
+    "image_url_block",
+    "link_block",
+    "video_block",
+    "assignment",
+    "document_block",
+    "content_list_item",
+    "subtitle",
+    "readonly",
 )
 
 
-def handle_content_block(content, context=None, module=None, allowed_blocks=ALLOWED_BLOCKS, previous_contents=None):
+def get_content_dict(content_type, id, value):
+    return {"type": content_type, "id": id, "value": value}
+
+
+def handle_content_block(
+    content,
+    context=None,
+    module=None,
+    allowed_blocks=ALLOWED_BLOCKS,
+    previous_contents=None,
+):
     """
     Handle different content types of a content block
 
@@ -75,95 +77,98 @@ def handle_content_block(content, context=None, module=None, allowed_blocks=ALLO
     """
     # todo: add all the content blocks
     # todo: sanitize user inputs!
-    if content['type'] not in allowed_blocks:
+    if content["type"] not in allowed_blocks:
         return
 
-    if content['type'] == 'text_block':
-        return {
-            'type': 'text_block',
-            'value': {
-                'text': handle_text(bleach.clean(content['value']['text'], strip=True))
-            }}
-    elif content['type'] == 'assignment':
+    id = content.get("id")
+    if id is None:
+        id = str(uuid.uuid4())
+
+    if content["type"] == "text_block":
+        content_type = "text_block"
+        value = {
+            "text": handle_text(bleach.clean(content["value"]["text"], strip=True))
+        }
+        return get_content_dict(
+            content_type=content_type,
+            id=id,
+            value=value,
+        )
+    elif content["type"] == "assignment":
         if module is None:
-            raise AssignmentParameterException('Module is missing for assignment')  # todo: define better exception
+            raise AssignmentParameterException(
+                "Module is missing for assignment"
+            )  # todo: define better exception
         if context is None:
-            raise AssignmentParameterException('Context is missing for assignment')
-        value = content['value']
-        if value.get('id') is not None:
-            assignment = get_object(Assignment, value.get('id'))
+            raise AssignmentParameterException("Context is missing for assignment")
+        value = content["value"]
+        if value.get("id") is not None:
+            assignment = get_object(Assignment, value.get("id"))
             if assignment.user_created and assignment.owner == context.user:
-                assignment.title = value.get('title')
-                assignment.assignment = value.get('assignment')
+                assignment.title = value.get("title")
+                assignment.assignment = value.get("assignment")
                 assignment.save()
         else:
             assignment = Assignment.objects.create(
-                title=value.get('title'),
-                assignment=value.get('assignment'),
+                title=value.get("title"),
+                assignment=value.get("assignment"),
                 owner=context.user,
                 module=module,
-                user_created=True
+                user_created=True,
             )
 
-        return {
-            'type': 'assignment',
-            'value': {
-                'assignment_id': assignment.id
-            }}
-    elif content['type'] == 'image_url_block':
-        return {
-            'type': 'image_url_block',
-            'value': {
-                'url': bleach.clean(content['value']['url'])
-            }}
-    elif content['type'] == 'link_block':
-        return {
-            'type': 'link_block',
-            'value': {
-                'text': bleach.clean(content['value']['text']),
-                'url': bleach.clean(content['value']['url'])
-            }
+        content_type = "assignment"
+        value = {"assignment_id": assignment.id}
+        return get_content_dict(content_type=content_type, id=id, value=value)
+    elif content["type"] == "image_url_block":
+        content_type = "image_url_block"
+        value = {"url": bleach.clean(content["value"]["url"])}
+        return get_content_dict(content_type=content_type, id=id, value=value)
+    elif content["type"] == "link_block":
+        content_type = "link_block"
+        value = {
+            "text": bleach.clean(content["value"]["text"]),
+            "url": bleach.clean(content["value"]["url"]),
         }
-    elif content['type'] == 'video_block':
-        return {
-            'type': 'video_block',
-            'value': {
-                'url': bleach.clean(content['value']['url'])
-            }}
-    elif content['type'] == 'document_block':
-        return {
-            'type': 'document_block',
-            'value': {
-                'url': bleach.clean(content['value']['url'])
-            }}
-    elif content['type'] == 'subtitle':
-        return {
-            'type': 'subtitle',
-            'value': {
-                'text': bleach.clean(content['value']['text'])
-            }
-        }
-    elif content['type'] == 'content_list_item':
-        if content.get('id') is not None:  # the list block existed already
-            previous_item = get_previous_item(previous_contents=previous_contents, item=content)
-            previous_content = previous_item.get('value')
+        return get_content_dict(content_type=content_type, id=id, value=value)
+    elif content["type"] == "video_block":
+        content_type = "video_block"
+        value = {"url": bleach.clean(content["value"]["url"])}
+        return get_content_dict(content_type=content_type, id=id, value=value)
+    elif content["type"] == "document_block":
+        content_type = "document_block"
+        value = {"url": bleach.clean(content["value"]["url"])}
+        return get_content_dict(content_type=content_type, id=id, value=value)
+    elif content["type"] == "subtitle":
+        content_type = "subtitle"
+        value = {"text": bleach.clean(content["value"]["text"])}
+        return get_content_dict(content_type=content_type, id=id, value=value)
+    elif content["type"] == "content_list_item":
+        if content.get("id") is not None:  # the list block existed already
+            previous_item = get_previous_item(
+                previous_contents=previous_contents, item=content
+            )
+            previous_content = previous_item.get("value")
         else:
             previous_content = None
-        value = [handle_content_block(c, context, module, previous_contents=previous_content) for c in
-                 content['contents']]
-        return {'type': 'content_list_item',
-                'value': value,
-                'id': content.get('id')}
-    elif content['type'] == 'readonly' and previous_contents is not None:
+        value = [
+            handle_content_block(c, context, module, previous_contents=previous_content)
+            for c in content["contents"]
+        ]
+        content_type = "content_list_item"
+        return get_content_dict(content_type=content_type, id=id, value=value)
+    elif content["type"] == "readonly" and previous_contents is not None:
         # get first item that matches the id
         # users can re-order readonly items, but we won't let them change them otherwise, so we just take the
         # item from before and ignore anything else
-        previous_item = get_previous_item(previous_contents=previous_contents, item=content)
+        previous_item = get_previous_item(
+            previous_contents=previous_contents, item=content
+        )
         if previous_item is None:
-            raise ContentTypeException('Readonly item found that is not allowed here')
+            raise ContentTypeException("Readonly item found that is not allowed here")
         return previous_item
 
-    raise ContentTypeException('Type did not match a case')
+    raise ContentTypeException("Type did not match a case")
 
 
 def set_user_defined_block_type(block_type):
diff --git a/server/books/tests/test_create_custom_content_block.py b/server/books/tests/test_create_custom_content_block.py
new file mode 100644
index 00000000..9c71c0de
--- /dev/null
+++ b/server/books/tests/test_create_custom_content_block.py
@@ -0,0 +1,284 @@
+import pytest
+from api.utils import get_object
+from assignments.models import Assignment
+from books.factories import ChapterFactory, ContentBlockFactory, ModuleFactory
+from books.models.contentblock import ContentBlock
+from core.logger import get_logger
+
+logger = get_logger(__name__)
+
+pytestmark = pytest.mark.django_db
+
+add_mutation = """
+mutation AddContentBlock($input: AddContentBlockInput!) {
+  addContentBlock(input: $input) {
+    newContentBlock {
+      id
+    }
+    errors
+    clientMutationId
+  }
+}
+
+"""
+
+update_mutation = """
+mutation MutateContentBlock($input: MutateContentBlockInput!) {
+        mutateContentBlock(input: $input) {
+            contentBlock {
+                id
+                contents
+                title
+                } 
+            }
+}
+"""
+
+
+def create_block_input(content_type, value):
+    return {
+        "contents": {
+            "type": content_type,
+            "value": value,
+        },
+        "title": "some title",
+        "type": "NORMAL",
+    }
+
+
+@pytest.mark.usefixtures("create_users")
+class TestCreateCustomContentBlock:
+    def _add_content_block(self, client, input):
+        module = ModuleFactory()
+        chapter = ChapterFactory(parent=module)
+        content_block = ContentBlockFactory(parent=chapter, module=module)
+        after = content_block.graphql_id
+        logger.info(after)
+        result = client.execute(
+            add_mutation,
+            variables={
+                "input": {
+                    "contentBlock": input,
+                    "after": after,
+                }
+            },
+        )
+        assert result.errors is None
+        assert result.data.get("addContentBlock", None).get("errors", None) is None
+        assert ContentBlock.objects.count() == 2
+        new_content_block_data = result.data.get("addContentBlock").get(
+            "newContentBlock"
+        )
+        new_block_id = new_content_block_data.get("id")
+        new_content_block = get_object(ContentBlock, new_block_id)
+        return new_content_block
+
+    def _update_content_block(self, client, input):
+        update_result = client.execute(update_mutation, variables=input)
+        assert update_result.errors is None
+        assert ContentBlock.objects.count() == 2
+        updated_content_block_id = (
+            update_result.data.get("mutateContentBlock").get("contentBlock").get("id")
+        )
+        updated_content_block = get_object(ContentBlock, updated_content_block_id)
+        return updated_content_block
+
+    def test_add_custom_content_block(self, teacher, get_client):
+        content_block_title = "A new Custom Content Block"
+        content_block_input = {
+            "contents": [
+                {
+                    "contents": [
+                        {
+                            "type": "text_block",
+                            "value": {"text": "<p>Some nested text</p>"},
+                        }
+                    ],
+                    "type": "content_list_item",
+                }
+            ],
+            "title": content_block_title,
+            "type": "NORMAL",
+        }
+        client = get_client(teacher)
+        new_content_block = self._add_content_block(
+            client=client, input=content_block_input
+        )
+        assert new_content_block.title == content_block_title
+        content_list_content = new_content_block.contents.raw_data[0]
+        logger.debug(content_list_content)
+        content_list_id = content_list_content.get("id")
+        assert content_list_id is not None
+        text_content = content_list_content.get("value")[0]
+        text_id = text_content.get("id")
+        assert text_id is not None
+
+        update_input = {
+            "input": {
+                "contentBlock": {
+                    "contents": [
+                        {
+                            "contents": [
+                                {
+                                    "type": "text_block",
+                                    "id": text_id,
+                                    "value": {"text": "<p>Some nested text</p>"},
+                                },
+                                {
+                                    "type": "text_block",
+                                    "value": {"text": "<p>Second nested text</p>"},
+                                },
+                            ],
+                            "id": content_list_id,
+                            "type": "content_list_item",
+                        }
+                    ],
+                    "title": content_block_title,
+                    "type": "NORMAL",
+                },
+                "id": new_content_block.graphql_id,
+            }
+        }
+
+        updated_content_block = self._update_content_block(client, update_input)
+        updated_content_list_content = updated_content_block.contents.raw_data[0]
+        updated_content_list_id = updated_content_list_content.get("id")
+        assert content_list_id == updated_content_list_id
+        updated_text_content = updated_content_list_content.get("value")[0]
+        updated_text_id = updated_text_content.get("id")
+        assert text_id == updated_text_id
+        added_text_content = updated_content_list_content.get("value")[1]
+        assert added_text_content.get("id") is not None
+        assert (
+            added_text_content.get("value").get("text") == "<p>Second nested text</p>"
+        )
+
+    def test_add_text_block_should_get_id(self, teacher, get_client):
+        client = get_client(teacher)
+        content_block_title = "A new Custom Content Block"
+        content_block_input = {
+            "contents": [
+                {
+                    "value": {"text": "Some text"},
+                    "type": "text_block",
+                }
+            ],
+            "title": content_block_title,
+            "type": "NORMAL",
+        }
+        new_content_block = self._add_content_block(
+            client=client, input=content_block_input
+        )
+        assert new_content_block.title == content_block_title
+        text_block = new_content_block.contents.raw_data[0]
+        text_id = text_block.get("id")
+        assert text_id is not None
+
+        update_input = {
+            "input": {
+                "contentBlock": {
+                    "contents": [
+                        {
+                            "id": text_id,
+                            "type": "text_block",
+                            "value": {"text": "<p>ein text</p>"},
+                        }
+                    ],
+                    "title": content_block_title,
+                    "type": "NORMAL",
+                },
+                "id": new_content_block.graphql_id,
+            }
+        }
+
+        updated_content_block = self._update_content_block(client, update_input)
+        updated_text = updated_content_block.contents.raw_data[0]
+        assert updated_text.get("id") == text_id
+
+    def test_add_text_block(self, teacher, get_client):
+        content_type = "text_block"
+        value = {"text": "<p>some text</p>"}
+        client = get_client(teacher)
+        input = create_block_input(content_type=content_type, value=value)
+        new_content_block = self._add_content_block(client=client, input=input)
+        text_block = new_content_block.contents.raw_data[0]
+        assert text_block.get("id") is not None
+        assert text_block.get("value").get("text") == value.get("text")
+
+    def test_add_assignment(self, teacher, get_client):
+        content_type = "assignment"
+        value = {"title": "Assignment title", "assignment": "Assignment text"}
+        client = get_client(teacher)
+        input = create_block_input(content_type=content_type, value=value)
+        new_content_block = self._add_content_block(client=client, input=input)
+        assignment_block = new_content_block.contents.raw_data[0]
+        logger.debug(assignment_block)
+        assert assignment_block.get("id") is not None
+        assert assignment_block.get("value").get("assignment_id") is not None
+        assert Assignment.objects.count() == 1
+        assignment = Assignment.objects.get(
+            pk=assignment_block.get("value").get("assignment_id")
+        )
+        assert assignment.title == value.get("title")
+        assert assignment.assignment == value.get("assignment")
+
+    def test_add_image_block(self, teacher, get_client):
+        content_type = "image_url_block"
+        value = {"url": "https://hep-verlag.ch/some-image"}
+        client = get_client(teacher)
+        input = create_block_input(content_type=content_type, value=value)
+        new_content_block = self._add_content_block(client=client, input=input)
+        image_block = new_content_block.contents.raw_data[0]
+        assert image_block.get("id") is not None
+        assert image_block.get("value").get("url") == value.get("url")
+
+    def test_add_link_block(self, teacher, get_client):
+        content_type = "link_block"
+        value = {"text": "link of the text", "url": "https://hep-verlag.ch/some-image"}
+        client = get_client(teacher)
+        input = create_block_input(content_type=content_type, value=value)
+        new_content_block = self._add_content_block(client=client, input=input)
+        link_block = new_content_block.contents.raw_data[0]
+        assert link_block.get("id") is not None
+        assert link_block.get("value").get("text") == value.get("text")
+        assert link_block.get("value").get("url") == value.get("url")
+
+    def test_add_video_block(self, teacher, get_client):
+        content_type = "video_block"
+        value = {"url": "https://hep-verlag.ch/some-video"}
+        client = get_client(teacher)
+        input = create_block_input(content_type=content_type, value=value)
+        new_content_block = self._add_content_block(client=client, input=input)
+        video_block = new_content_block.contents.raw_data[0]
+        assert video_block.get("id") is not None
+        assert video_block.get("value").get("url") == value.get("url")
+
+    def test_add_document_block(self, teacher, get_client):
+        content_type = "document_block"
+        value = {"url": "https://hep-verlag.ch/some-document"}
+        client = get_client(teacher)
+        input = create_block_input(content_type=content_type, value=value)
+        new_content_block = self._add_content_block(client=client, input=input)
+        document_block = new_content_block.contents.raw_data[0]
+        assert document_block.get("id") is not None
+        assert document_block.get("value").get("url") == value.get("url")
+
+    def test_add_subtitle(self, teacher, get_client):
+        content_type = "subtitle"
+        value = {"text": "some subtitle"}
+        client = get_client(teacher)
+        input = create_block_input(content_type=content_type, value=value)
+        new_content_block = self._add_content_block(client=client, input=input)
+        subtitle_block = new_content_block.contents.raw_data[0]
+        assert subtitle_block.get("id") is not None
+        assert subtitle_block.get("value").get("text") == value.get("text")
+
+    # def test_add_readonly(self):
+    #     content_type = "readonly"
+    #     value = {"text": "some subtitle"}
+    #     client = get_client(teacher)
+    #     input = create_block_input(content_type=content_type, value=value)
+    #     new_content_block = self._add_content_block(client=client, input=input)
+    #     subtitle_block = new_content_block.contents.raw_data[0]
+    #     assert subtitle_block.get("id") is not None
+    #     assert subtitle_block.get("value").get("text") == value.get("text")
diff --git a/server/books/tests/test_custom_content_blocks.py b/server/books/tests/test_custom_content_blocks.py
new file mode 100644
index 00000000..24a174f0
--- /dev/null
+++ b/server/books/tests/test_custom_content_blocks.py
@@ -0,0 +1,145 @@
+from django.test import RequestFactory
+from graphene.test import Client
+from graphql_relay import to_global_id
+
+from api.schema import schema
+from books.factories import ModuleFactory
+from books.models import Chapter, ContentBlock
+from core.tests.base_test import SkillboxTestCase
+from users.models import User, SchoolClass
+
+
+class CustomContentTestCase(SkillboxTestCase):
+    def setUp(self):
+        self.module = ModuleFactory()
+        self.chapter = Chapter(title="Hello")
+        self.module.add_child(instance=self.chapter)
+        self.createDefault()
+        content_block = ContentBlock(title="bla", slug="bla")
+        self.chapter_id = to_global_id("ChapterNode", self.chapter.id)
+        self.chapter.specific.add_child(instance=content_block)
+        self.user = User.objects.get(username="teacher")
+        school_class2 = SchoolClass.objects.get(name="second_class")
+        school_class2.users.add(self.user)
+        school_class2.save()
+
+        request = RequestFactory().get("/")
+        request.user = self.user
+        assert content_block.id is not None
+        self.content_block_id = to_global_id("ContentBlockNode", content_block.id)
+
+        self.client = Client(schema=schema, context_value=request)
+
+    def test_custom_content_blocks(self):
+        self.assertEqual(self.user.school_classes.count(), 2)
+        chapterQuery = """
+        query ChapterQuery($id: ID!) {
+          chapter(id: $id) {
+            id
+            title
+            contentBlocks {
+              id
+              title
+            }
+          }
+        }
+        """
+        result = self.get_client().execute(
+            chapterQuery, variables={"id": self.chapter_id}
+        )
+        self.assertIsNone(result.errors)
+        self.assertEqual(len(result.data.get("chapter").get("contentBlocks")), 1)
+
+        custom_content_block = ContentBlock(
+            title="own", slug="own", user_created=True, owner=self.user
+        )
+        self.chapter.specific.add_child(instance=custom_content_block)
+        result = self.get_client().execute(
+            chapterQuery, variables={"id": self.chapter_id}
+        )
+        self.assertEqual(len(result.data.get("chapter").get("contentBlocks")), 2)
+
+        for school_class in self.user.school_classes.all():
+            custom_content_block.visible_for.add(school_class)
+
+        result = self.get_client().execute(
+            chapterQuery, variables={"id": self.chapter_id}
+        )
+        self.assertEqual(len(result.data.get("chapter").get("contentBlocks")), 2)
+
+    def test_mutate_own_content_block(self):
+        query = """
+        query ContentBlockQuery($id: ID!) {
+            contentBlock(id: $id) {
+                contents
+                title
+            }
+        } 
+        """
+
+        res = self.get_client().execute(query, variables={"id": self.content_block_id})
+        self.assertIsNone(res.errors)
+        self.assertEqual(res.data["contentBlock"]["title"], "bla")
+
+        mutation = """
+        mutation MutateContentBlock($input: MutateContentBlockInput!) {
+            mutateContentBlock(input: $input) {
+              contentBlock {
+                 contents
+                 title
+              } 
+            }
+        }
+        """
+
+        new_content = {
+            "id": "",
+            "type": "text_block",
+            "value": {"text": "new text \n a new line"},
+        }
+
+        variables = {
+            "input": {
+                "id": self.content_block_id,
+                "contentBlock": {
+                    "contents": [new_content],
+                    "title": "new title",
+                    "type": "NORMAL",
+                },
+            }
+        }
+
+        mutation_result = self.get_client().execute(mutation, variables=variables)
+        self.assertIsNone(mutation_result.errors)
+        content_block = mutation_result.data["mutateContentBlock"]["contentBlock"]
+        self.assertEqual(content_block["title"], "new title")
+        self.assertEqual(
+            content_block["contents"][0]["value"]["text"],
+            "<p>new text</p>\n<p>a new line</p>",
+        )
+
+        content_with_list = {
+            "id": "",
+            "type": "text_block",
+            "value": {"text": "<ul><li>Hallo</li><li>Velo</li></ul>"},
+        }
+        other_variables = {
+            "input": {
+                "id": self.content_block_id,
+                "contentBlock": {
+                    "contents": [content_with_list],
+                    "title": "title for list content",
+                    "type": "NORMAL",
+                },
+            }
+        }
+        list_mutation_result = self.get_client().execute(
+            mutation, variables=other_variables
+        )
+        self.assertIsNone(list_mutation_result.errors)
+        content_block = list_mutation_result.data["mutateContentBlock"]["contentBlock"]
+        self.assertEqual(content_block["title"], "title for list content")
+        self.assertEqual(
+            content_block["contents"][0]["value"]["text"],
+            "<ul><li>Hallo</li><li>Velo</li></ul>",
+        )
diff --git a/server/books/tests/test_own_content_blocks.py b/server/books/tests/test_own_content_blocks.py
deleted file mode 100644
index c743eaaa..00000000
--- a/server/books/tests/test_own_content_blocks.py
+++ /dev/null
@@ -1,144 +0,0 @@
-from django.test import TestCase, RequestFactory
-from graphene.test import Client
-from graphql_relay import to_global_id
-
-from api.schema import schema
-from books.factories import ModuleFactory
-from books.models import Chapter, ContentBlock
-from core.tests.base_test import SkillboxTestCase
-from users.models import User, SchoolClass
-from users.services import create_users
-
-
-class OwnContentTestCase(SkillboxTestCase):
-    def setUp(self):
-        self.module = ModuleFactory()
-        self.chapter = Chapter(title='Hello')
-        self.module.add_child(instance=self.chapter)
-        self.createDefault()
-        content_block = ContentBlock(title='bla', slug='bla')
-        self.chapter_id = to_global_id('ChapterNode', self.chapter.id)
-        self.chapter.specific.add_child(instance=content_block)
-        self.user = User.objects.get(username='teacher')
-        school_class2 = SchoolClass.objects.get(name='second_class')
-        school_class2.users.add(self.user)
-        school_class2.save()
-
-        request = RequestFactory().get('/')
-        request.user = self.user
-        assert content_block.id is not None
-        self.content_block_id = to_global_id('ContentBlockNode', content_block.id)
-
-        self.client = Client(schema=schema, context_value=request)
-
-    def test_custom_content_blocks(self):
-        self.assertEqual(self.user.school_classes.count(), 2)
-        chapterQuery = """
-        query ChapterQuery($id: ID!) {
-          chapter(id: $id) {
-            id
-            title
-            contentBlocks {
-              id
-              title
-            }
-          }
-        }
-        """
-        result = self.get_client().execute(chapterQuery, variables={
-            "id": self.chapter_id
-        })
-        self.assertIsNone(result.errors)
-        self.assertEqual(len(result.data.get('chapter').get('contentBlocks')), 1)
-
-        custom_content_block = ContentBlock(title='own', slug='own', user_created=True, owner=self.user)
-        self.chapter.specific.add_child(instance=custom_content_block)
-        result = self.get_client().execute(chapterQuery, variables={
-            "id": self.chapter_id
-        })
-        self.assertEqual(len(result.data.get('chapter').get('contentBlocks')), 2)
-
-        for school_class in self.user.school_classes.all():
-            custom_content_block.visible_for.add(school_class)
-
-        result = self.get_client().execute(chapterQuery, variables={
-            "id": self.chapter_id
-        })
-        self.assertEqual(len(result.data.get('chapter').get('contentBlocks')), 2)
-
-    def test_mutate_own_content_block(self):
-        query = """
-        query ContentBlockQuery($id: ID!) {
-            contentBlock(id: $id) {
-                contents
-                title
-            }
-        } 
-        """
-
-        res = self.get_client().execute(query, variables={'id': self.content_block_id})
-        self.assertIsNone(res.errors)
-        self.assertEqual(res.data['contentBlock']['title'], 'bla')
-
-        mutation = """
-        mutation MutateContentBlock($input: MutateContentBlockInput!) {
-            mutateContentBlock(input: $input) {
-              contentBlock {
-                 contents
-                 title
-              } 
-            }
-        }
-        """
-
-        new_content = {
-            'id': '',
-            'type': 'text_block',
-            'value': {
-                'text': 'new text \n a new line'
-            }
-        }
-
-        variables = {
-            'input': {
-                'id': self.content_block_id,
-                'contentBlock': {
-                    'contents': [
-                        new_content
-                    ],
-                    'title': 'new title',
-                    'type': 'NORMAL'
-                }
-            }
-        }
-
-        mutation_result = self.get_client().execute(mutation, variables=variables)
-        self.assertIsNone(mutation_result.errors)
-        content_block = mutation_result.data['mutateContentBlock']['contentBlock']
-        self.assertEqual(content_block['title'], 'new title')
-        self.assertEqual(content_block['contents'][0]['value']['text'], '<p>new text</p>\n<p>a new line</p>')
-
-        content_with_list = {
-            'id': '',
-            'type': 'text_block',
-            'value': {
-                'text': '<ul><li>Hallo</li><li>Velo</li></ul>'
-            }
-        }
-        other_variables = {
-            'input': {
-                'id': self.content_block_id,
-                'contentBlock': {
-                    'contents': [
-                        content_with_list
-                    ],
-                    'title': 'title for list content',
-                    'type': 'NORMAL'
-                }
-            }
-        }
-        list_mutation_result = self.get_client().execute(mutation, variables=other_variables)
-        self.assertIsNone(list_mutation_result.errors)
-        content_block = list_mutation_result.data['mutateContentBlock']['contentBlock']
-        self.assertEqual(content_block['title'], 'title for list content')
-        self.assertEqual(content_block['contents'][0]['value']['text'], '<ul><li>Hallo</li><li>Velo</li></ul>')