diff --git a/backend/src/graphql/resolver/UserResolver.test.ts b/backend/src/graphql/resolver/UserResolver.test.ts
index 7d71d74b1..f46d0a9bc 100644
--- a/backend/src/graphql/resolver/UserResolver.test.ts
+++ b/backend/src/graphql/resolver/UserResolver.test.ts
@@ -53,6 +53,7 @@ import {
   searchAdminUsers,
   searchUsers,
   user as userQuery,
+  checkUsername,
 } from '@/seeds/graphql/queries'
 import { bibiBloxberg } from '@/seeds/users/bibi-bloxberg'
 import { bobBaumeister } from '@/seeds/users/bob-baumeister'
@@ -2442,6 +2443,34 @@ describe('UserResolver', () => {
       })
     })
   })
+
+  describe('check username', () => {
+    describe('reserved alias', () => {
+      it('returns false', async () => {
+        await expect(
+          query({ query: checkUsername, variables: { username: 'root' } }),
+        ).resolves.toMatchObject({
+          data: {
+            checkUsername: false,
+          },
+          errors: undefined,
+        })
+      })
+    })
+
+    describe('valid alias', () => {
+      it('returns true', async () => {
+        await expect(
+          query({ query: checkUsername, variables: { username: 'valid' } }),
+        ).resolves.toMatchObject({
+          data: {
+            checkUsername: true,
+          },
+          errors: undefined,
+        })
+      })
+    })
+  })
 })
 
 describe('printTimeDuration', () => {
diff --git a/backend/src/seeds/graphql/queries.ts b/backend/src/seeds/graphql/queries.ts
index bc8fa95e8..ce7efbfc3 100644
--- a/backend/src/seeds/graphql/queries.ts
+++ b/backend/src/seeds/graphql/queries.ts
@@ -22,6 +22,12 @@ export const queryOptIn = gql`
   }
 `
 
+export const checkUsername = gql`
+  query ($username: String!) {
+    checkUsername(username: $username)
+  }
+`
+
 export const transactionsQuery = gql`
   query ($currentPage: Int = 1, $pageSize: Int = 25, $order: Order = DESC) {
     transactionList(currentPage: $currentPage, pageSize: $pageSize, order: $order) {