1 files changed, 125 insertions, 0 deletions
diff --git a/preact/compat/test/browser/PureComponent.test.js b/preact/compat/test/browser/PureComponent.test.js
new file mode 100644
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+++ b/preact/compat/test/browser/PureComponent.test.js
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+import React, { createElement } from 'preact/compat';
+import { setupRerender } from 'preact/test-utils';
+import { setupScratch, teardown } from '../../../test/_util/helpers';
+
+describe('PureComponent', () => {
+	/** @type {HTMLDivElement} */
+	let scratch;
+
+	/** @type {() => void} */
+	let rerender;
+
+	beforeEach(() => {
+		scratch = setupScratch();
+		rerender = setupRerender();
+	});
+
+	afterEach(() => {
+		teardown(scratch);
+	});
+
+	it('should be a class', () => {
+		expect(React)
+			.to.have.property('PureComponent')
+			.that.is.a('function');
+	});
+
+	it('should pass props in constructor', () => {
+		let spy = sinon.spy();
+		class Foo extends React.PureComponent {
+			constructor(props) {
+				super(props);
+				spy(this.props, props);
+			}
+		}
+
+		React.render(<Foo foo="bar" />, scratch);
+
+		let expected = { foo: 'bar' };
+		expect(spy).to.be.calledWithMatch(expected, expected);
+	});
+
+	it('should ignore the __source variable', () => {
+		const pureSpy = sinon.spy();
+		const appSpy = sinon.spy();
+		let set;
+		class Pure extends React.PureComponent {
+			render() {
+				pureSpy();
+				return <div>Static</div>;
+			}
+		}
+
+		const App = () => {
+			const [, setState] = React.useState(0);
+			appSpy();
+			set = setState;
+			return <Pure __source={{}} />;
+		};
+
+		React.render(<App />, scratch);
+		expect(appSpy).to.be.calledOnce;
+		expect(pureSpy).to.be.calledOnce;
+
+		set(1);
+		rerender();
+		expect(appSpy).to.be.calledTwice;
+		expect(pureSpy).to.be.calledOnce;
+	});
+
+	it('should only re-render when props or state change', () => {
+		class C extends React.PureComponent {
+			render() {
+				return <div />;
+			}
+		}
+		let spy = sinon.spy(C.prototype, 'render');
+
+		let inst = React.render(<C />, scratch);
+		expect(spy).to.have.been.calledOnce;
+		spy.resetHistory();
+
+		inst = React.render(<C />, scratch);
+		expect(spy).not.to.have.been.called;
+
+		let b = { foo: 'bar' };
+		inst = React.render(<C a="a" b={b} />, scratch);
+		expect(spy).to.have.been.calledOnce;
+		spy.resetHistory();
+
+		inst = React.render(<C a="a" b={b} />, scratch);
+		expect(spy).not.to.have.been.called;
+
+		inst.setState({});
+		rerender();
+		expect(spy).not.to.have.been.called;
+
+		inst.setState({ a: 'a', b });
+		rerender();
+		expect(spy).to.have.been.calledOnce;
+		spy.resetHistory();
+
+		inst.setState({ a: 'a', b });
+		rerender();
+		expect(spy).not.to.have.been.called;
+	});
+
+	it('should update when props are removed', () => {
+		let spy = sinon.spy();
+		class App extends React.PureComponent {
+			render() {
+				spy();
+				return <div>foo</div>;
+			}
+		}
+
+		React.render(<App a="foo" />, scratch);
+		React.render(<App />, scratch);
+		expect(spy).to.be.calledTwice;
+	});
+
+	it('should have "isPureReactComponent" property', () => {
+		let Pure = new React.PureComponent();
+		expect(Pure.isReactComponent).to.deep.equal({});
+	});
+});