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JavaScript Testing

Jest​

  • Jest is one of the most popular testing library for JavaScript (https://jestjs.io/).
  • Jest is not fully supported by Vite but it is good to know some basics of Jest.
  • For example, if we have a simple function:
function multiply(x, y) {
  return x * y;
}
  • Test case for the multiply function looks like the following:
test("test 2 * 3", () => {
  expect(multiply(2, 3)).toBe(6);
});

  • test function takes two arguments: a unique name and a test case. You can also use the alias it.

  • expect function is used when you want to test some values. It is normally used with matchers.

  • toBe is a Jest matcher that checks the value that function returns.

  • Find more information about matchers in the Jest documentation.

  • You can use the describe to group together related test cases.

describe("App component tests", () => {
  test("component renders", () => {
    // 1st test case
  });

  test("header text is shown", () => {
    // 2nd test case
  });
});