What is TDD
Test Driven Development aka TDD is a software development practice that focuses on creating unit test before developing the actual code.
So you don’t write a single line of program until you have the test.
Examples
So if you want to write a program that adds number. You will need to write the test cases first.
Writing the unit test with jest first
sum.test.js
const sum = require("./sum");
test("properly adds two numbers", () => {
expect(sum(1, 2)).toBe(3);
expect(sum(0, 0)).toBe(0);
expect(sum(-4, 2).toBe(-2);
expect(sum(0.5, 0.1).toBe(0.6);
// other cases needed to
});
And write the program you wanted
sum.js
function sum(a, b) {
return a + b;
}
function helper() {
console.log("Helper");
}
module.exports = sum;