Unit testing
We already know that unit testing is the process of verifying the correctness of individual “units” of code: namely, functions and methods. The goal of unit testing is to ensure that each separate unit performs its task correctly, which, in turn, increases confidence in the reliability of the entire application.
export function sum(a: number, b: number): number {
return a + b;
}
test('adds 1 + 2 to equal 3', () => {
expect(sum(1, 2)).toBe(3);
});
The above represents the most basic and simplest test of a function that adds two values. The test code itself is a function that calls a special method, expect, which takes a value and then has a series of methods allowing for the checking and comparing of results.
Looking at this code, the first question that might come to mind is, is it really necessary to write another three lines of tests for such a simple three-line function? And why test such a function at all? I would answer...
