A pattern of unit testing I like to do is “table-driven tests” (popularized by Go).

I like this style for doing tests where you want to assert a wide variety of inputs/output pairs with minimal boilerplate.

describe("is_a_cat", () => {
	const tests = [
		{ input: "", expected: false },
		{ input: "snoop dogg", expected: false },
		{ input: "kitty party", expected: true },
		{ input: "tons of cats!", expected: true },
	];

	for (const t of tests) {
		test(`${t.input} contains cats? ${t.expected}`, () => {
			expect(is_a_cat(t.input)).toEqual(t.expected);
		});
	}
});

In this test suite we construct an array of input/output pairs which we then iterate over and create a test case for each combination.

I like to create a dynamic test title to help debugging since table-driven tests can be hard to troubleshoot without a description.

---

Like this post?
Why don't you let me know on Twitter: @danawoodman