polish(incremental): improve IncrementalPublisher return test

Use a stream that never resolves to better demonstrate how there will be a definite pending promise.

Calling return on the underlying graph flushes the nextQueue anyway.

Author: yaacovCR

src/execution/__tests__/stream-test.ts

@@ -2331,16 +2331,12 @@ describe('Execute: stream directive', () => {
   });
   it('Returns underlying async iterables when returned generator is returned', async () => {
     let returned = false;
-    let index = 0;
     const iterable = {
       [Symbol.asyncIterator]: () => ({
-        next: () => {
-          const friend = friends[index++];
-          if (friend == null) {
-            return Promise.resolve({ done: true, value: undefined });
-          }
-          return Promise.resolve({ done: false, value: friend });
-        },
+        next: () =>
+          new Promise(() => {
+            /* never resolves */
+          }),
         return: () => {
           returned = true;
         },
@@ -2349,11 +2345,8 @@ describe('Execute: stream directive', () => {
 
     const document = parse(`
       query {
-        friendList @stream(initialCount: 1) {
+        friendList @stream(initialCount: 0) {
           id
-          ... @defer {
-            name
-          }
         }
       }
     `);
@@ -2371,21 +2364,16 @@ describe('Execute: stream directive', () => {
     const result1 = executeResult.initialResult;
     expectJSON(result1).toDeepEqual({
       data: {
-        friendList: [
-          {
-            id: '1',
-          },
-        ],
+        friendList: [],
       },
-      pending: [
-        { id: '0', path: ['friendList', 0] },
-        { id: '1', path: ['friendList'] },
-      ],
+      pending: [{ id: '0', path: ['friendList'] }],
       hasNext: true,
     });
+
+    const result2Promise = iterator.next();
     const returnPromise = iterator.return();
 
-    const result2 = await iterator.next();
+    const result2 = await result2Promise;
     expectJSON(result2).toDeepEqual({
       done: true,
       value: undefined,