fix console & buffered console assert behaviour (#5576)

* fix console & buffered console assert behaviour

* add console assert fix to changelog

* fix tests to match two different assertion error style in node 6 and above

* refactor arguments passed from console.assert to the assert module

CHANGELOG.md

@@ -13,6 +13,8 @@
  ([#5560](https://github.com/facebook/jest/pull/5560))
 * `[jest-config]` Make it possible to merge `transform` option with preset
  ([#5505](https://github.com/facebook/jest/pull/5505))
+* `[jest-util]` Fix `console.assert` behavior in custom & buffered consoles
+ ([#5576](https://github.com/facebook/jest/pull/5576))
 
 ### Features
 

packages/jest-util/src/Console.js

@@ -10,6 +10,7 @@
 
 import type {LogType, LogMessage, LogCounters, LogTimers} from 'types/Console';
 
+import assert from 'assert';
 import {format} from 'util';
 import {Console} from 'console';
 import chalk from 'chalk';
@@ -48,8 +49,10 @@ export default class CustomConsole extends Console {
  }
 
  assert(...args: Array<any>) {
- if (args[0]) {
- this._log('assert', format(...args.slice(1)));
+ try {
+ assert(...args);
+ } catch (error) {
+ this._log('assert', error.toString());
  }
  }
 

packages/jest-util/src/__tests__/buffered_console.test.js

@@ -23,16 +23,30 @@ describe('CustomConsole', () => {
  });
 
  describe('assert', () => {
- test('log when the assertion is truthy', () => {
+ test('do not log when the assertion is truthy', () => {
+ _console.assert(true);
+
+ expect(stdout()).toMatch('');
+ });
+
+ test('do not log when the assertion is truthy and there is a message', () => {
  _console.assert(true, 'ok');
 
- expect(stdout()).toMatch('ok');
+ expect(stdout()).toMatch('');
  });
 
- test('do not log when the assertion is falsy', () => {
+ test('log the assertion error when the assertion is falsy', () => {
+ _console.assert(false);
+
+ expect(stdout()).toMatch('AssertionError');
+ expect(stdout()).toMatch('false == true');
+ });
+
+ test('log the assertion error when the assertion is falsy with another message argument', () => {
  _console.assert(false, 'ok');
 
- expect(stdout()).toEqual('');
+ expect(stdout()).toMatch('AssertionError');
+ expect(stdout()).toMatch('ok');
  });
  });
 

packages/jest-util/src/__tests__/console.test.js

@@ -24,16 +24,30 @@ describe('CustomConsole', () => {
  });
 
  describe('assert', () => {
- test('log when the assertion is truthy', () => {
+ test('do not log when the assertion is truthy', () => {
+ _console.assert(true);
+
+ expect(_stdout).toMatch('');
+ });
+
+ test('do not log when the assertion is truthy and there is a message', () => {
  _console.assert(true, 'ok');
 
- expect(_stdout).toMatch('ok');
+ expect(_stdout).toMatch('');
  });
 
- test('do not log when the assertion is falsy', () => {
+ test('log the assertion error when the assertion is falsy', () => {
+ _console.assert(false);
+
+ expect(_stdout).toMatch('AssertionError');
+ expect(_stdout).toMatch('false == true');
+ });
+
+ test('log the assertion error when the assertion is falsy with another message argument', () => {
  _console.assert(false, 'ok');
 
- expect(_stdout).toEqual('');
+ expect(_stdout).toMatch('AssertionError');
+ expect(_stdout).toMatch('ok');
  });
  });
 

packages/jest-util/src/buffered_console.js

@@ -15,6 +15,7 @@ import type {
  LogTimers,
 } from 'types/Console';
 
+import assert from 'assert';
 import {Console} from 'console';
 import {format} from 'util';
 import chalk from 'chalk';
@@ -63,8 +64,10 @@ export default class BufferedConsole extends Console {
  }
 
  assert(...args: Array<any>) {
- if (args[0]) {
- this._log('assert', format(...args.slice(1)));
+ try {
+ assert(...args);
+ } catch (error) {
+ this._log('assert', error.toString());
  }
  }