Implement errors for to less or to many categories and test it

backend/src/constants/categories.js

@@ -0,0 +1,5 @@
+// this file is duplicated in `backend/src/config/metadata.js` and `webapp/constants/metadata.js`
+export default {
+  CATEGORIES_MIN: 1,
+  CATEGORIES_MAX: 3,
+}

backend/src/schema/resolvers/groups.js

@@ -3,6 +3,7 @@ import { v4 as uuid } from 'uuid'
 // Wolle: import { isEmpty } from 'lodash'
 import { UserInputError } from 'apollo-server'
 import CONFIG from '../../config'
+import categories from '../../constants/categories'
 // Wolle: import { mergeImage, deleteImage } from './images/images'
 import Resolver from './helpers/Resolver'
 // Wolle: import { filterForMutedUsers } from './helpers/filterForMutedUsers'
@@ -69,6 +70,12 @@ export default {
     CreateGroup: async (_parent, params, context, _resolveInfo) => {
       const { categoryIds } = params
       delete params.categoryIds
+      if (!categoryIds || categoryIds.length < categories.CATEGORIES_MIN) {
+        throw new UserInputError('To Less Categories!')
+      }
+      if (categoryIds && categoryIds.length > categories.CATEGORIES_MAX) {
+        throw new UserInputError('To Many Categories!')
+      }
       params.id = params.id || uuid()
       const session = context.driver.session()
       const writeTxResultPromise = session.writeTransaction(async (transaction) => {

backend/src/schema/resolvers/groups.spec.js

@@ -416,12 +416,34 @@ describe('CreateGroup', () => {
       )
     })
 
-    it('`disabled` and `deleted` default to `false`', async () => {
+    it('"disabled" and "deleted" default to "false"', async () => {
       const expected = { data: { CreateGroup: { disabled: false, deleted: false } } }
       await expect(mutate({ mutation: createGroupMutation, variables })).resolves.toMatchObject(
         expected,
       )
     })
+
+    describe('categories', () => {
+      describe('not even one', () => {
+        it('throws error: "To Less Categories!"', async () => {
+          const { errors } = await mutate({
+            mutation: createGroupMutation,
+            variables: { ...variables, categoryIds: null },
+          })
+          expect(errors[0]).toHaveProperty('message', 'To Less Categories!')
+        })
+      })
+
+      describe('four', () => {
+        it('throws error: "To Many Categories!"', async () => {
+          const { errors } = await mutate({
+            mutation: createGroupMutation,
+            variables: { ...variables, categoryIds: ['cat9', 'cat4', 'cat15', 'cat27'] },
+          })
+          expect(errors[0]).toHaveProperty('message', 'To Many Categories!')
+        })
+      })
+    })
   })
 })