I am testing my React component to verify a callback function behavior delayed by setTimeout but I am receiving the error below despite my fake timer is already triggered within an act block.
The error is as below:
C:\dev\node\node.exe --require "C:\dev\JetBrains\IntelliJ IDEA 2021.1.1\plugins\JavaScriptLanguage\helpers\jest-intellij\lib\jest-intellij-stdin-fix.js" C:\Users\Reph0\Desktop\my-app\node_modules\react-scripts\bin\react-scripts.js test --colors --reporters "C:\dev\JetBrains\IntelliJ IDEA 2021.1.1\plugins\JavaScriptLanguage\helpers\jest-intellij\lib\jest-intellij-reporter.js" --verbose "--testNamePattern=^Timeout component should randomize value until more than 0\.9$" --runTestsByPath C:/Users/Reph0/Desktop/my-app/src/TimeoutComponent.spec.tsx
console.error
Warning: An update to TimeoutComponent inside a test was not wrapped in act(...).
When testing, code that causes React state updates should be wrapped into act(...):
act(() => {
/* fire events that update state */
});
/* assert on the output */
This ensures that you're testing the behavior the user would see in the browser. Learn more at https://reactjs.org/link/wrap-tests-with-act
at TimeoutComponent (C:\Users\Reph0\Desktop\my-app\src\TimeoutComponent.tsx:8:35)
The component
import * as React from "react";
interface Props {
getValue: () => Promise<number>;
}
const TimeoutComponent: React.FC<Props> = (props) => {
const [value, setValue] = React.useState<number>(0);
React.useEffect(() => {
if (value < 0.9) {
const timeoutId = setTimeout(() => props.getValue().then(setValue), 300);
return () => {
clearTimeout(timeoutId);
};
}
}, [value]);
return (
<>
<p>
Value: <span id="value">{value}</span>
</p>
</>
);
};
export default TimeoutComponent;
The test
import { render } from "@testing-library/react";
import React from "react";
import { act } from "react-dom/test-utils";
import TimeoutComponent from "./TimeoutComponent";
const getValue = jest.fn();
describe("Timeout component", () => {
beforeEach(() => {
jest.resetAllMocks();
jest.useFakeTimers();
});
afterEach(() => {
jest.useRealTimers();
});
it("should randomize value until more than 0.9", () => {
getValue
.mockResolvedValueOnce(0.1)
.mockResolvedValueOnce(0.2)
.mockResolvedValueOnce(0.3)
.mockResolvedValueOnce(0.4)
.mockResolvedValueOnce(0.7)
.mockResolvedValueOnce(0.92)
.mockResolvedValueOnce(0.6);
render(<TimeoutComponent getValue={getValue} />);
act(() => {
jest.runAllTimers();
});
expect(getValue).toBeCalledTimes(6);
});
});
Here is my package.json
{
"name": "my-app",
"version": "0.1.0",
"private": true,
"dependencies": {
"@testing-library/jest-dom": "^5.11.4",
"@testing-library/react": "^11.1.0",
"@testing-library/user-event": "^12.1.10",
"@types/jest": "^26.0.15",
"@types/node": "^12.0.0",
"@types/react": "^17.0.0",
"@types/react-dom": "^17.0.0",
"react": "^17.0.2",
"react-dom": "^17.0.2",
"react-scripts": "4.0.3",
"typescript": "^4.1.2",
"web-vitals": "^1.0.1"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": [
"react-app",
"react-app/jest"
]
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
}
}
Here is the link to my codesandbox but seems like jest.runAllTimers() doesn't work well there.
Appreciate if someone can give a hand :)