Test-Driven Development

Learn about test-driven development and how to write a test using the Jest framework.

Perhaps a brief explanation of that concept is in order. Test-driven development (TDD) comes from the Extreme Programming movement. Its core idea is to create a test that verifies the code’s behavior before actually writing that code. Let’s write a function that adds two numbers.

Writing test

Before writing code, we’ll create the following test using the Jest framework:

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describe('sum tests', () => {
test('should return two when given one and one', () => {
const result = sum(1, 1);
expect(result).toBe(2);
});
});

Obviously, this test fails because we lack a ...

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