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How do you test React components?

Q: How do you test React components?

**Core concept (TL;DR).** Use **React Testing Library** (RTL) with a runner like **Jest** or **Vitest**. RTL's philosophy is to test **behaviour the user sees**, not implementation details: render the component, query elements by role/text, simulate user interactions, and assert on the resulting output. Add **Playwright/Cypress** for end-to-end flows. Render → query → interact → assert render() <rect x="148" y="58" width="110"

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Discuss common testing methodologies and tools used for unit and integration testing of React components.

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A behaviour-focused RTL test

import { render, screen } from "@testing-library/react";
import userEvent from "@testing-library/user-event";
import { useState } from "react";

function Counter() {
  const [n, setN] = useState(0);
  return <button onClick={() => setN(n + 1)}>Count: {n}</button>;
}

// the test (runs under Jest/Vitest):
test("increments on click", async () => {
  render(<Counter />);
  const btn = screen.getByRole("button", { name: /count: 0/i });
  await userEvent.click(btn);
  expect(screen.getByRole("button")).toHaveTextContent("Count: 1");
});

export default Counter; // (component under test)

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