Jest testing

https://jestjs.io/docs/getting-started

Test callback

• index.js

const test = (fetch) => {
	return fetch("test");
};

module.exports = test;

• index.test.js

const testFunction = require("./index");

test("test callback function", (done) => {

	function fetch(data) {

			try {

					expect(data).toBe("test_fake");

					done();

			} catch (error) {

					done(error);

			}

	}

	testFunction(fetch);

});

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Test string => toMatch(some_regex)

Test value => toBe(value_expect)

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Test promise:

• index.js

  const fetchData = (fetch) => {
    return new Promise((resolve, reject) => {
      resolve("hello");
    });
  };
  
  module.exports = fetchData;
  
  

• index.test.js

const fetchData = require("./index");

test("test promise", () => {
  return fetchData().then((data) => {
    expect(data).toBe("hello");
  });
});

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Test function with async/await

index.test.js

const fetchData = require("./index");

test("test async function", async () => {
  const data = await fetchData();
  expect(data).toBe("hello");
});

index.js