Add 'resolveOnNextTick' to use in tests (graphql#2778)

instead of Node.js specific methods

src/__testUtils__/__tests__/resolveOnNextTick-test.js

@@ -0,0 +1,21 @@
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+
+import resolveOnNextTick from '../resolveOnNextTick';
+
+describe('resolveOnNextTick', () => {
+  it('resolves promise on the next tick', async () => {
+    const output = [];
+
+    const promise1 = resolveOnNextTick().then(() => {
+      output.push('second');
+    });
+    const promise2 = resolveOnNextTick().then(() => {
+      output.push('third');
+    });
+    output.push('first');
+
+    await Promise.all([promise1, promise2]);
+    expect(output).to.deep.equal(['first', 'second', 'third']);
+  });
+});

src/__testUtils__/resolveOnNextTick.js

@@ -0,0 +1,3 @@
+export default function resolveOnNextTick(): Promise<void> {
+  return Promise.resolve(undefined);
+}

src/execution/__tests__/executor-test.js

@@ -115,11 +115,7 @@ describe('Execute: Handles basic execution tasks', () => {
     };
 
     function promiseData() {
-      return new Promise((resolve) => {
-        process.nextTick(() => {
-          resolve(data);
-        });
-      });
+      return Promise.resolve(data);
     }
 
     const DataType = new GraphQLObjectType({

src/execution/__tests__/mutations-test.js

@@ -1,6 +1,8 @@
 import { expect } from 'chai';
 import { describe, it } from 'mocha';
 
+import resolveOnNextTick from '../../__testUtils__/resolveOnNextTick';
+
 import { parse } from '../../language/parser';
 
 import { GraphQLInt } from '../../type/scalars';
@@ -29,24 +31,18 @@ class Root {
     return this.numberHolder;
   }
 
-  promiseToChangeTheNumber(newNumber: number): Promise<NumberHolder> {
-    return new Promise((resolve) => {
-      process.nextTick(() => {
-        resolve(this.immediatelyChangeTheNumber(newNumber));
-      });
-    });
+  async promiseToChangeTheNumber(newNumber: number): Promise<NumberHolder> {
+    await resolveOnNextTick();
+    return this.immediatelyChangeTheNumber(newNumber);
   }
 
   failToChangeTheNumber(): NumberHolder {
     throw new Error('Cannot change the number');
   }
 
-  promiseAndFailToChangeTheNumber(): Promise<NumberHolder> {
-    return new Promise((_resolve, reject) => {
-      process.nextTick(() => {
-        reject(new Error('Cannot change the number'));
-      });
-    });
+  async promiseAndFailToChangeTheNumber(): Promise<NumberHolder> {
+    await resolveOnNextTick();
+    throw new Error('Cannot change the number');
   }
 }
 

src/subscription/__tests__/subscribe-test.js

@@ -3,6 +3,8 @@ import EventEmitter from 'events';
 import { expect } from 'chai';
 import { describe, it } from 'mocha';
 
+import resolveOnNextTick from '../../__testUtils__/resolveOnNextTick';
+
 import type { DocumentNode } from '../../language/ast';
 import { parse } from '../../language/parser';
 
@@ -244,7 +246,7 @@ describe('Subscription Initialization Phase', () => {
           importantEmail: {
             type: GraphQLString,
             subscribe: async () => {
-              await new Promise(setImmediate);
+              await resolveOnNextTick();
               return eventEmitterAsyncIterator(pubsub, 'importantEmail');
             },
           },
@@ -262,6 +264,8 @@ describe('Subscription Initialization Phase', () => {
       `),
     });
 
+    expect(subscription).to.have.property('next');
+
     pubsub.emit('importantEmail', {
       importantEmail: {},
     });