Restructure test case

Add another describe block around it to group the following test case with it.

test/set-items.ut.js

@@ -11,16 +11,19 @@ import { iterable, expectExactlySameMembers } from './helper'
 
 
 describe('setItems - updating the list of selectable items', () => {
-  it('should remove items from selection that don\'t exist anymore', () => {
-    const state = init()
+  describe('remove selected items', () => {
+    it('should remove items from selection that don\'t exist anymore', () => {
+      const state = init()
 
-    const newState = flow(
-      setItems(iterable(['A', 'B', 'C', 'D'])),
-      setSelection(['B', 'C']),
-      setItems(iterable(['A', 'C', 'D']))
-    )(state)
+      const newState = flow(
+        setItems(iterable(['A', 'B', 'C', 'D'])),
+        setSelection(['B', 'C']),
+        setItems(iterable(['A', 'C', 'D']))
+      )(state)
+
+      expectExactlySameMembers(getSelection(newState), ['C'])
+    })
 
-    expectExactlySameMembers(getSelection(newState), ['C'])
   })
 
   it('should remove item from anchor that doesn\'t exist anymore', () => {