node-data-modeling/test/function-guards.js

"use strict";

const expect = require("chai").expect;

const dm = require("../src");

describe("function guards", () => {
	it("should accept a correctly-behaving function", () => {
		let guardedFunction = dm.guard([dm.string(), dm.number()], dm.boolean(), function (str, num) {
			expect(str).to.equal("hello world");
			expect(num).to.equal(42);
			return true;
		});

		guardedFunction("hello world", 42);
	});

	it("should throw on an invalid return value type", () => {
		let guardedFunction = dm.guard([dm.string(), dm.number()], dm.boolean(), function (str, num) {
			return "not a boolean";
		});

		expect(() => {
			guardedFunction("hello world", 42);
		}).to.throw("Expected a boolean, got a string instead");
	});

	it("should throw on an invalid argument type", () => {
		let guardedFunction = dm.guard([dm.string(), dm.number()], dm.boolean(), function (str, num) {
			return true;
		});

		expect(() => {
			guardedFunction(false, 42);
		}).to.throw("Expected a string, got a boolean instead");
	});

	it("should throw on a missing argument", () => {
		let guardedFunction = dm.guard([dm.string(), dm.number()], dm.boolean(), function (str, num) {
			return true;
		});

		expect(() => {
			guardedFunction("hello world");
		}).to.throw("Value is required for property '<unknown>'");
	});

	it(" ... but not when that argument is optional", () => {
		let guardedFunction = dm.guard([dm.string(), dm.number().optional()], dm.boolean(), function (str, num) {
			expect(str).to.equal("hello world");
			expect(num).to.equal(null);
			return true;
		});

		guardedFunction("hello world");
	});

	it("should correctly handle defaults", () => {
		let guardedFunction = dm.guard([dm.string(), dm.number().default(42)], dm.boolean(), function (str, num) {
			expect(str).to.equal("hello world");
			expect(num).to.equal(42);
			return true;
		});

		guardedFunction("hello world");
	});

	let SomeType = dm.createType("SomeType", {
		value: dm.string()
	});

	let guardedTypeFunction = dm.guard([SomeType], dm.nothing(), function (instance) {
		expect(instance.value).to.equal("foo");
	});

	it("should allow correct instances for a type rule", () => {
		guardedTypeFunction(SomeType({
			value: "foo"
		}));
	});

	it("should reject other values for that rule", () => {
		expect(() => {
			guardedTypeFunction("hello world");
		}).to.throw("Expected an instance of SomeType, got a string instead");
	});

	let SomeTraitType = dm.createType("SomeTraitType", {
		value: dm.string()
	});

	let SomeTrait = dm.createTrait("SomeTrait", {
		traitValue: dm.string()
	});

	SomeTraitType.implements(SomeTrait, {
		traitValue: "SomeTraitType"
	});

	let guardedTraitFunction = dm.guard([SomeTrait], dm.nothing(), function (instance) {
		expect(instance.value).to.equal("foo");
		expect(instance.traitValue).to.equal("SomeTraitType");
	});

	it("should allow correct instances for a trait rule", () => {
		guardedTraitFunction(SomeTraitType({
			value: "foo"
		}));
	});

	it ("should reject instances that do not have the trait", () => {
		expect(() => {
			guardedTraitFunction(SomeType({
				value: "foo"
			}));
		}).to.throw("Expected object of a type with the SomeTrait trait, got an instance of SomeType instead");
	});

	it("should reject other values for that rule", () => {
		expect(() => {
			guardedTraitFunction("hello world");
		}).to.throw("Expected object of a type with the SomeTrait trait, got a string instead");
	});
});