Tone.js/Tone/event/PatternGenerator.test.ts

import { expect } from "chai";
import { PatternGenerator } from "./PatternGenerator";

describe("PatternGenerator", () => {

	function getArrayValues(gen: Iterator<any>, length: number): any[] {
		const ret: any[] = [];
		for (let i = 0; i < length; i++) {
			ret.push(gen.next().value);
		}
		return ret;
	}

	context("API", () => {

		it("can be constructed with an array and type", () => {
			const pattern = PatternGenerator([0, 1, 2, 3], "down");
			expect(getArrayValues(pattern, 10)).to.deep.equal([3, 2, 1, 0, 3, 2, 1, 0, 3, 2]);
		});

		it("can be resized smaller when the index is after the previous length", () => {
			const values = [0, 1, 2, 3, 4];
			const pattern = PatternGenerator(values);
			expect(pattern.next().value).to.equal(0);
			values.shift();
			expect(pattern.next().value).to.equal(2);
		});

		it("throws an error with an empty array", () => {
			expect(() => {
				const pattern = PatternGenerator([]);
				pattern.next();
			}).to.throw(Error);
		});
	});

	context("Patterns", () => {

		it("does the up pattern", () => {
			const pattern = PatternGenerator([0, 1, 2, 3], "up");
			expect(getArrayValues(pattern, 6)).to.deep.equal([0, 1, 2, 3, 0, 1]);
		});

		it("does the down pattern", () => {
			const pattern = PatternGenerator([0, 1, 2, 3], "down");
			expect(getArrayValues(pattern, 6)).to.deep.equal([3, 2, 1, 0, 3, 2]);
		});

		it("does the upDown pattern", () => {
			const pattern = PatternGenerator([0, 1, 2, 3], "upDown");
			expect(getArrayValues(pattern, 10)).to.deep.equal([0, 1, 2, 3, 2, 1, 0, 1, 2, 3]);
		});

		it("does the downUp pattern", () => {
			const pattern = PatternGenerator([0, 1, 2, 3], "downUp");
			expect(getArrayValues(pattern, 10)).to.deep.equal([3, 2, 1, 0, 1, 2, 3, 2, 1, 0]);
		});

		it("does the alternateUp pattern", () => {
			const pattern = PatternGenerator([0, 1, 2, 3, 4], "alternateUp");
			expect(getArrayValues(pattern, 10)).to.deep.equal([0, 2, 1, 3, 2, 4, 3, 0, 2, 1]);
		});

		it("does the alternateDown pattern", () => {
			const pattern = PatternGenerator([0, 1, 2, 3, 4], "alternateDown");
			expect(getArrayValues(pattern, 10)).to.deep.equal([4, 2, 3, 1, 2, 0, 1, 4, 2, 3]);
		});

		it("outputs random elements from the values", () => {
			const values = [0, 1, 2, 3, 4];
			const pattern = PatternGenerator(values, "random");
			for (let i = 0; i < 10; i++) {
				expect(values.indexOf(pattern.next().value)).to.not.equal(-1);
			}
		});

		it("does randomOnce pattern", () => {
			const pattern = PatternGenerator([4, 5, 6, 7, 8], "randomOnce");
			expect(getArrayValues(pattern, 10).sort()).to.deep.equal([4, 4, 5, 5, 6, 6, 7, 7, 8, 8]);
		});
                
		it("randomly walks up or down 1 step without repeating", () => {
			const values = [0, 1, 2, 3, 4];
			const pattern = PatternGenerator(values, "randomWalk");
			let currentIndex = values.indexOf(pattern.next().value);
			for (let i = 0; i < 10; i++) {
				const nextIndex = values.indexOf(pattern.next().value);
				expect(currentIndex).to.not.equal(nextIndex);
				// change always equals 1
				expect(Math.abs(currentIndex - nextIndex)).to.equal(1);
				currentIndex = nextIndex;
			}
		});
	});
});