fix(VirtualTimeScheduler): rework flush so it won't lose actions

spec/schedulers/VirtualTimeScheduler-spec.ts

@@ -1,6 +1,5 @@
 import { expect } from 'chai';
-import * as Rx from 'rxjs/Rx';
-import { SchedulerAction, Subscription, VirtualAction, VirtualTimeScheduler } from 'rxjs';
+import { SchedulerAction, VirtualAction, VirtualTimeScheduler } from 'rxjs';
 
 /** @test {VirtualTimeScheduler} */
 describe('VirtualTimeScheduler', () => {
@@ -67,7 +66,7 @@ describe('VirtualTimeScheduler', () => {
     let count = 0;
     const expected = [100, 200, 300];
 
-    v.schedule<string>(function(this: SchedulerAction<string>, state: string) {
+    v.schedule<string>(function (this: SchedulerAction<string>, state: string) {
       if (++count === 3) {
         return;
       }
@@ -82,12 +81,60 @@ describe('VirtualTimeScheduler', () => {
 
   it('should not execute virtual actions that have been rescheduled before flush', () => {
     const v = new VirtualTimeScheduler();
-    let messages: string[] = [];
-    let action: VirtualAction<string> = <VirtualAction<string>> v.schedule(function(state: string) {
-      messages.push(state);
-    }, 10, 'first message');
-    action = <VirtualAction<string>> action.schedule('second message' , 10);
+    const messages: string[] = [];
+
+    const action: VirtualAction<string> = <VirtualAction<string>> v.schedule(
+      state => messages.push(state),
+      10,
+      'first message'
+    );
+
+    action.schedule('second message', 10);
     v.flush();
+
     expect(messages).to.deep.equal(['second message']);
   });
+
+  it('should execute only those virtual actions that fall into the maxFrames timespan', function () {
+    const MAX_FRAMES = 50;
+    const v = new VirtualTimeScheduler(VirtualAction, MAX_FRAMES);
+    const messages: string[] = ['first message', 'second message', 'third message'];
+
+    const actualMessages: string[] = [];
+
+    messages.forEach((message, index) => {
+      v.schedule(
+        (state: string) => actualMessages.push(state),
+        index * MAX_FRAMES,
+        message
+      );
+    });
+
+    v.flush();
+
+    expect(actualMessages).to.deep.equal(['first message', 'second message']);
+    expect(v.actions.map(a => a.state)).to.deep.equal(['third message']);
+  });
+
+  it('should pick up actions execution where it left off after reaching previous maxFrames limit', function () {
+    const MAX_FRAMES = 50;
+    const v = new VirtualTimeScheduler(VirtualAction, MAX_FRAMES);
+    const messages: string[] = ['first message', 'second message', 'third message'];
+
+    const actualMessages: string[] = [];
+
+    messages.forEach((message, index) => {
+      v.schedule(
+        state => actualMessages.push(state),
+        index * MAX_FRAMES,
+        message
+      );
+    });
+
+    v.flush();
+    v.maxFrames = 2 * MAX_FRAMES;
+    v.flush();
+
+    expect(actualMessages).to.deep.equal(messages);
+  });
 });

src/internal/scheduler/VirtualTimeScheduler.ts

@@ -25,7 +25,10 @@ export class VirtualTimeScheduler extends AsyncScheduler {
     const {actions, maxFrames} = this;
     let error: any, action: AsyncAction<any>;
 
-    while ((action = actions.shift()) && (this.frame = action.delay) <= maxFrames) {
+    while ((action = actions[0]) && action.delay <= maxFrames) {
+      actions.shift();
+      this.frame = action.delay;
+
       if (error = action.execute(action.state, action.delay)) {
         break;
       }