Plugin for unexpected to allow for testing the full virtual DOM, and against the shallow renderer (replaces unexpected-react-shallow)
!
See the blog post for an introduction: https://medium.com/@bruderstein/the-missing-piece-to-the-react-testing-puzzle-c51cd30df7a0
npm install --save-dev unexpected unexpected-react
If you want to assert over the whole virtual DOM, then you need to emulate the DOM (note this library is not designed for use in the browser - it may be possible, but at the very least, you'll need to disable the react-devtools)
If you don't need the virtual DOM, and you're just using the shallow renderer,
then the order of the requires is not important, and you obviously don't need the emulateDom.js require.
// First require your DOM emulation file (see below)
require( '../testHelpers/emulateDom');
var unexpected = require('unexpected');
// then require unexpected-react
var unexpectedReact = require('unexpected-react');
// then react
var React = require('react/addons');
// define our instance of the `expect` function to use
const expect = unexpected.clone()
.use(unexpectedReact);The emulateDom file depends on whether you want to use domino, or jsdom
For jsdom:
// emulateDom.js - jsdom variant
if (typeof document === 'undefined') {
const jsdom = require('jsdom').jsdom;
global.document = jsdom('');
global.window = global.document.defaultView;
for (let key in global.window) {
if (!global[key]) {
global[key] = global.window[key];
}
}
}For domino:
// emulateDom.js - domino variant
if (typeof document === 'undefined') {
const domino = require('domino');
global.window = domino.createWindow('');
global.document = global.window.document;
global.navigator = { userAgent: 'domino' };
for (let key in global.window) {
if (!global[key]) {
global[key] = global.window[key];
}
}
}From that point on, you can require the components you want to test, and write your tests.
For the shallow renderer, you can assert on the renderer itself (you can also write the same assertion for the result of getRenderOutput())
it('renders with content', function () {
var renderer = TestUtils.createRenderer();
renderer.render(<SomeComponent id={125} />);
return expect(renderer, 'to have rendered',
<div id={125}>
Some simple content
</div>
);
});If this fails for some reason, you get a nicely formatted error, with the differences highlighted:
If you've emulated the DOM, you can write a similar test, but using ReactDOM.render() (or TestUtils.renderIntoDocument())
it('renders with content', function () {
var component = TestUtils.renderIntoDocument(<SomeComponent id={125} />);
return expect(component, 'to have rendered',
<div id={125}>
Some simple content
</div>
);
});
Note the major difference between the shallow renderer and the "normal" renderer, is that child components are also rendered. That is easier to see with these example components:
var Text = React.createClass({
render() {
return <span>{this.props.content}</span>;
}
});
var App = React.createClass({
render() {
return (
<div className="testing-is-fun">
<Text content="hello" />
<Text content="world" />
</div>
);
}
});Rendering the App component with the shallow renderer will not render the spans, only the
Text component with the props. If you wanted to test for the content of the span elements, you'd
need to use TestUtils.renderIntoDocument(...), or ReactDOM.render(...)
Because unexpected-react be default ignores wrapper elements, and also "extra" children (child
nodes that appear in the actual render, but are not in the expected result), it is possible to test both scenarios
with the full renderer. To demonstrate, all the following tests will pass:
it('renders the Text components with the spans with the full renderer', function () {
var component = TestUtils.renderIntoDocument(<App />);
return expect(component, 'to have rendered',
<App>
<div className="testing-is-fun">
<Text content="hello">
<span>hello</span>
</Text>
<Text content="world">
<span>world</span>
</Text>
</div>
</App>
);
});
it('renders the Text nodes with the full renderer', function () {
var component = TestUtils.renderIntoDocument(<App />);
return expect(component, 'to have rendered',
<div className="testing-is-fun">
<Text content="hello" />
<Text content="world" />
</div>
);
});
it('renders the spans with the full renderer', function () {
var component = TestUtils.renderIntoDocument(<App />);
return expect(component, 'to have rendered',
<div className="testing-is-fun">
<span>hello</span>
<span>world</span>
</div>
);
});The first test shows the full virtual DOM that gets rendered. The second test skips the <App> "wrapper" component,
and leaves out the <span> children of the <Text> components. The third tests skips both the <App> wrapper component,
and the <Text> wrapper component.
Notice that the result from expect is returned from the it block. The unexpected-react assertions are currently
asynchronous, and can therefore return a promise. When using mocha, you can return
the promise from the it block, and mocha will wait for the promise to be resolved.
All the assertions can be used with an instance of the shallow renderer, a shallow rendered component
(i.e. the return value from renderer.getRenderOutput()), or a normally rendered component (i.e. the return
value from ReactDOM.render() (React.render() in React <= 0.13.x), or TestUtils.renderIntoDocument()).
You can make the following assertions:
// Extra props and children from the render are ignored
expect(component, 'to have rendered', <div className="parent" />);
// The span "two" is missing here, but it is ignored.
expect(component, 'to have rendered',
<div id="main">
<span>one</span>
<span>three</span>
</div>
);
// The following assertion will fail, as 'four' does not exist
expect(renderer, 'to have rendered',
<div id="main">
<span>one</span>
<span>four</span>
</div>
);If you want to check for an exact render, use 'to have exactly rendered'.
Alternatively, if you don't care about extra props, but want to check that there are no extra child nodes, use 'to have rendered with all children'
Note that exactly implies with all children, so you using both options is not necessary.
Normally wrappers (elements that simply wrap other components) are ignored. This can be useful if you have higher order
components wrapping your components, you can simply ignore them in your tests (they will be shown greyed out
if there is a "real" error). If you want to test that there are no extra wrappers, simply add with all wrappers to the
assertion.
// The span "two" is missing here, as is `className="parent"`
// The missing span will cause an assertion error, but the extra prop will be ignored
// due to `to have rendered with all children` being used
expect(renderer, 'to have rendered with all children',
<div id="main">
<span>one</span>
<span>three</span>
</div>
);// The span "two" is missing here, as is `className="parent"`
// This will cause an assertion error,
// due to `to have exactly rendered` being used
expect(renderer, 'to have exactly rendered',
<div id="main">
<span>one</span>
<span>three</span>
</div>
);It's possible to check for a part of the subtree, without testing the entire returned tree. This allows you to test specific elements, without writing brittle tests that break when the structure changes.
// This will pass, as `<span className="middle">two</span>` can be found in the renderers output
expect(renderer, 'to contain', <span>two</span>);Notice that the extra className="middle" in the <span className="middle">two</span> is ignored,
in a similar way to the to have rendered assertion.
You can override this behaviour by using 'to contain exactly', and 'to contain with all children'
// This will fail, as `<span>two</span>` cannot be found in the renderers output, due to
// the missing `className="middle"` prop
expect(renderer, 'to contain exactly', <span>two</span>);The same thing applies to children for 'to contain' as for 'to have rendered'.
String content is split up by React when you have embedded variables.
For example:
{
render: function() {
return (
<div>
Click on {this.props.clickCount} times
</div>
);
}
}This actually produces 3 "child" elements of the div, Click on , the clickCount and the times
To make this simpler, unexpected-react-shallow concatenates these values so you can simply test the
previous example as follows:
expect(renderer, 'to have rendered',
<div>
Clicked on 3 times
</div>);If you use the exactly variants of the assertions, you will need to split up your assertion in the same way
e.g.
expect(renderer, 'to have exactly rendered',
<div>
Clicked on {3} times
</div>);When using the normal renderer, unexpected-react makes use of react-render-hook,
which utilises the code from the React devtools. As there is no way for react-render-hook
to know when a test is completed, it has to keep a reference to every rendered component. Whilst this shouldn't normally be an issue,
if you use a test runner that keeps the process alive (such as wallaby.js), it is a good idea to call
unexpectedReact.clearAll() in a global beforeEach() or afterEach() block. This clears the cache of rendered nodes.
- There are some performance optimisations to do. The performance suffers a bit due to the possible asynchronous nature of the inline assertions. Most of the time these will be synchronous, and hence we don't need to pay the price.
- Some helper functions, allowing directly calling functions passed to props may make working with events and the shallow renderer easier
We welcome pull requests, bug reports, and extra test cases. If you find something that doesn't work as you believe it should, or where the output isn't as good as it could be, raise an issue!
Huge thanks to @Munter for unexpected-dom, and along with @dmatteo from Podio for handing over the unexpected-react name.
Unexpected is a great library to work with, and I offer my sincere thanks to @sunesimonsen and @papandreou, who have created an assertion library that makes testing JavaScript a joy.
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