diff --git a/packages/core/admin/admin/src/content-manager/components/RelationInputDataManager/utils/tests/diffRelations.test.js b/packages/core/admin/admin/src/content-manager/components/RelationInputDataManager/utils/tests/diffRelations.test.js
new file mode 100644
index 0000000000..8c5a91b5ff
--- /dev/null
+++ b/packages/core/admin/admin/src/content-manager/components/RelationInputDataManager/utils/tests/diffRelations.test.js
@@ -0,0 +1,98 @@
+import { diffRelations } from '../diffRelations';
+
+describe('diffRelations', () => {
+  test('given that the browserState and serverState are the same it should return an array with two empty arrays', () => {
+    const browserState = [
+      {
+        id: 1,
+        name: 'Relation 1',
+      },
+      {
+        id: 2,
+        name: 'Relation 2',
+      },
+    ];
+    const serverState = [
+      {
+        id: 1,
+        name: 'Relation 1',
+      },
+      {
+        id: 2,
+        name: 'Relation 2',
+      },
+    ];
+
+    expect(diffRelations(browserState, serverState)).toStrictEqual([[], []]);
+  });
+
+  test('given that the browserState is missing an ID that is in the serverState I should have that ID in the disconnect array', () => {
+    const browserState = [
+      {
+        id: 1,
+        name: 'Relation 1',
+      },
+    ];
+    const serverState = [
+      {
+        id: 1,
+        name: 'Relation 1',
+      },
+      {
+        id: 2,
+        name: 'Relation 2',
+      },
+    ];
+
+    expect(diffRelations(browserState, serverState)).toStrictEqual([[], [2]]);
+  });
+
+  test('given that the browserState has one ID more than the serverState I should have that ID in the connect array', () => {
+    const browserState = [
+      {
+        id: 1,
+        name: 'Relation 1',
+      },
+      {
+        id: 2,
+        name: 'Relation 2',
+      },
+    ];
+    const serverState = [
+      {
+        id: 1,
+        name: 'Relation 1',
+      },
+    ];
+
+    expect(diffRelations(browserState, serverState)).toStrictEqual([[2], []]);
+  });
+
+  test('given that the browserState is completely different to the serverState the return value should reflect this', () => {
+    const browserState = [
+      {
+        id: 1,
+        name: 'Relation 1',
+      },
+      {
+        id: 2,
+        name: 'Relation 2',
+      },
+    ];
+    const serverState = [
+      {
+        id: 3,
+        name: 'Relation 3',
+      },
+      {
+        id: 4,
+        name: 'Relation 4',
+      },
+    ];
+
+    expect(diffRelations(browserState, serverState)).toStrictEqual([
+      [1, 2],
+      [3, 4],
+    ]);
+  });
+});