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vitest-plugin-set

Declarative JS tests with lazy evaluation for vitest.

Getting Started

Install vitest-plugin-set using yarn:

Motivation

RSpec took the ruby world by storm with its declarative method of TDD. Since moving to JavaScript, I've wanted a similar way of declaring the setup for my tests. Here's what you would normally do to declare a test:

Some notes:

1. Because of scoping in javascript, we have to declare our variables outside the beforeEach blocks in order to reference them. 2. Our beforeEach blocks contain _all_ of the setup code necessary which in this trivial example is at least 3 lines per test. 3. We can override variables in nested scopes, but following the chain is non-trivial because the actual variable declaration might be several layers up.

Here's what the same tests look like with using set from vitest-plugin-set:

Even in this trivial example, things are much easier to follow.

1. We can declare firstName and lastName as variables that we can then reference in our beforeEach blocks. 2. We can break up the large beforeEach blocks into several distinct set blocks. 3. We can easily set defaults in outer scopes (which may or may not be used within a particular test saving performance) and then overriding the values in nested blocks.

Why set?

In JavaScript, let is a keyword so the next closest word is...set (which still keeps the meaning of what we're doing

• settings variables (lazily)).

Usage

If you want, you can import set from vitest-plugin-set at the top of every test:

If you want to install set as a global, you can modify the test section of your vitest.config.js to include:

Example

Here's an example test that tests set itself:

Description from the npm listing.