React: Unit test failures on React 15.2.1

[jakepusateri]

Bug

Unit tests using shallow rendering fail on 'TypeError: Cannot read property 'onSetDisplayName' of null'.

I can't seem to get TestUtils into jsfiddle, but here is the build output and code snippet.

import expect from 'expect';
import TestUtils from 'react-addons-test-utils';
import React from 'react';
import BlurInput from '...';
...
    beforeEach(function () {
        props = {value: '1', onChange: function () {}};
        expect.spyOn(props, 'onChange');
        let renderer = TestUtils.createRenderer();
        renderer.render(<BlurInput {...props} />);
        instance = getInstance(renderer);
        componentTree = renderer.getRenderOutput();
    });
    it('reflects value to underlying input', function () {
        expect(componentTree.props.value).toBe('1');
        expect(instance.state.value).toBe('1');
    });

00:04:18.742   1) BlurInput "before each" hook for "reflects value to underlying input":
00:04:18.742      TypeError: Cannot read property 'onSetDisplayName' of null
00:04:18.742       at new ShallowComponentWrapper (node_modules/react/lib/ReactTestUtils.js:349:33)
00:04:18.742       at ReactShallowRenderer._render (node_modules/react/lib/ReactTestUtils.js:399:20)
00:04:18.742       at _batchedRender (node_modules/react/lib/ReactTestUtils.js:381:12)
00:04:18.742       at ReactDefaultBatchingStrategyTransaction.Mixin.perform (node_modules/react/lib/Transaction.js:138:20)
00:04:18.742       at Object.ReactDefaultBatchingStrategy.batchedUpdates (node_modules/react/lib/ReactDefaultBatchingStrategy.js:63:19)
00:04:18.742       at Object.batchedUpdates (node_modules/react/lib/ReactUpdates.js:98:20)
00:04:18.742       at ReactShallowRenderer.render (node_modules/react/lib/ReactTestUtils.js:374:16)
00:04:18.742       at Context.<anonymous> (BlurInput-test.js:19:18)

What is the expected behavior?
Unit test should run normally.

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?
15.2.1 has this issue.
15.2.0 does not.

[zpao]

I think this is because you are running a prod version of React in your tests. The testutils aren't entirely compatible with that (and generally expect that you're running in dev mode). This case in particular is going to blame to #7189 because we actually removed some dead code that wasn't used in production builds. The way did that removal broke your use case though.

cc @gaearon. The line at issue is ReactInstrumentation.debugTool.onSetDisplayName(this._debugID, displayName); which is going to fail because of https://github.com/facebook/react/pull/7189/files#diff-6bee1fd898dc3a6fef767ec0e6446e41R14

[gaearon]

Oops, I thought TestUtils are dev-only. Were we technically supporting running them in prod?

[jakepusateri]

They had worked up until now, but it seems reasonable to not have them supported in production. It should be pretty simple to adjust my build to not set NODE_ENV=production during the test run.

[vvo]

Was using NODE_ENV=production to avoid warnings in my npm test. I guess I will have to write better tests and code :)

[gaearon]

We’ll include a fix in the next version. Sorry I messed it up

[gaearon]

This will be fixed by #7246.

[sashafklein]

@zpao @gaearon -- Is there a solution in mind going forward for CI testing? We run our tests on CircleCI, and want them to run in the production environment so they're as representative as possible of how the code will actually behave in production. Switching that test environment to dev feels like it would defeat one of the central purposes of a CI server.

[gaearon]

There should be no difference (except perf and warnings) between dev and prod versions of React. This is super important for us at Facebook and we are committed to keeping it this way. So I don't think running unit tests with prod env would be valuable to you.

[gaearon]

(End to end tests are a different matter but you wouldn't need TestUtils for them anyway.)