Remove cpu backend in tfjs-node testing, use fake instead. (#3082)

BUG Remove cpu backend in tfjs-node testing, use fake instead.

Author: lina128

tfjs-node/src/image_test.ts

@@ -1,6 +1,6 @@
 /**
  * @license
- * Copyright 2019 Google Inc. All Rights Reserved.
+ * Copyright 2020 Google Inc. All Rights Reserved.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
@@ -14,10 +14,12 @@
  * limitations under the License.
  * =============================================================================
  */
-
-import {memory, setBackend, test_util} from '@tensorflow/tfjs';
+import {memory, registerBackend, setBackend, test_util} from '@tensorflow/tfjs';
+// tslint:disable-next-line: no-imports-from-dist
+import {TestKernelBackend} from '@tensorflow/tfjs-core/dist/jasmine_util';
 import * as fs from 'fs';
 import {promisify} from 'util';
+
 import {getImageType, ImageType} from './image';
 import * as tf from './index';
 
@@ -221,14 +223,18 @@ describe('decode images', () => {
 
   it('throw error if backend is not tensorflow', async done => {
     try {
-      setBackend('cpu');
+      const testBackend = new TestKernelBackend();
+      registerBackend('fake', () => testBackend);
+      setBackend('fake');
+
       const uint8array = await getUint8ArrayFromImage(
           'test_objects/images/image_png_test.png');
       tf.node.decodeImage(uint8array);
       done.fail();
     } catch (err) {
       expect(err.message)
-          .toBe('Expect the current backend to be "tensorflow", but got "cpu"');
+          .toBe(
+              'Expect the current backend to be "tensorflow", but got "fake"');
       setBackend('tensorflow');
       done();
     }

tfjs-node/src/nodejs_kernel_backend_test.ts

@@ -16,6 +16,9 @@
  */
 
 import * as tf from '@tensorflow/tfjs';
+// tslint:disable-next-line: no-imports-from-dist
+import {TestKernelBackend} from '@tensorflow/tfjs-core/dist/jasmine_util';
+
 import {createTensorsTypeOpAttr, createTypeOpAttr, ensureTensorflowBackend, getTFDType, nodeBackend, NodeJSKernelBackend} from './nodejs_kernel_backend';
 
 describe('delayed upload', () => {
@@ -74,12 +77,16 @@ describe('Exposes Backend for internal Op execution.', () => {
 
   it('throw error if backend is not tensorflow', async done => {
     try {
-      tf.setBackend('cpu');
+      const testBackend = new TestKernelBackend();
+      tf.registerBackend('fake', () => testBackend);
+      tf.setBackend('fake');
+
       ensureTensorflowBackend();
       done.fail();
     } catch (err) {
       expect(err.message)
-          .toBe('Expect the current backend to be "tensorflow", but got "cpu"');
+          .toBe(
+              'Expect the current backend to be "tensorflow", but got "fake"');
       tf.setBackend('tensorflow');
       done();
     }

tfjs-node/src/run_tests.ts

@@ -35,8 +35,12 @@ process.on('unhandledRejection', e => {
   throw e;
 });
 
-jasmine_util.setTestEnvs(
-    [{name: 'test-tensorflow', backendName: 'tensorflow', flags: {}}]);
+jasmine_util.setTestEnvs([{
+  name: 'test-tensorflow',
+  backendName: 'tensorflow',
+  flags: {},
+  isDataSync: true
+}]);
 
 const IGNORE_LIST: string[] = [
   // Always ignore version tests:
@@ -90,11 +94,11 @@ if (process.platform === 'win32') {
       'maxPool test-tensorflow {} [x=[3,3,1] f=[2,2] s=1 ignores NaNs');
 }
 
-const coreTests = 'node_modules/@tensorflow/tfjs-core/dist/**/*_test.js';
-const nodeTests = 'src/**/*_test.ts';
-
 const runner = new jasmineCtor();
-runner.loadConfig({spec_files: [coreTests, nodeTests], random: false});
+runner.loadConfig({spec_files: ['src/**/*_test.ts'], random: false});
+// Also import tests from core.
+// tslint:disable-next-line: no-imports-from-dist
+import '@tensorflow/tfjs-core/dist/tests';
 
 if (process.env.JASMINE_SEED) {
   runner.seed(process.env.JASMINE_SEED);