node-data-modeling/test/traits.js

"use strict";

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

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

/* FIXME: Slot rule testing */
/* FIXME: Function guard signature matching */

let GitSource = dm.createTrait("GitSource", {
	stringify: dm.function([], dm.string())
});

let GithubSource, CrytoGitSource, ExternalGitSource, sourceOne, sourceTwo, randomGitSource;

describe("traits", () => {
	it("should allow valid trait implementations", () => {
		GithubSource = dm.createType("GithubSource", {
			username: dm.string(),
			repository: dm.string()
		}).implements(GitSource, {
			stringify: dm.guard([], dm.string(), function () {
				return `https://github.com/${this.username}/${this.repository}.git`;
			})
		});

		CrytoGitSource = dm.createType("CrytoGitSource", {
			username: dm.string(),
			repository: dm.string()
		}).implements(GitSource, {
			stringify: dm.guard([], dm.string(), function () {
				return `http://git.cryto.net/${this.username}/${this.repository}.git`;
			})
		});
	});

	it("should produce working trait functionality", () => {
		sourceOne = GithubSource({
			username: "joepie91",
			repository: "node-bhttp"
		});

		expect(sourceOne.stringify()).to.equal("https://github.com/joepie91/node-bhttp.git");

		sourceTwo = CrytoGitSource({
			username: "joepie91",
			repository: "node-bhttp"
		});

		expect(sourceTwo.stringify()).to.equal("http://git.cryto.net/joepie91/node-bhttp.git");
	});

	let guardedFunc = dm.guard([GitSource], dm.nothing(), function (source) {
		expect(source.stringify()).to.be.a("string");
	});

	it("should allow an instance of any type with the correct trait to be passed into a trait-guarded function", () => {
		guardedFunc(sourceOne);
		guardedFunc(sourceTwo);
	});

	it("should reject an instance of a type that does not have the correct trait", () => {
		let SomeType = dm.createType("SomeType", {
			value: dm.string()
		});

		let instance = SomeType({
			value: "foo"
		});

		expect(() => {
			guardedFunc(instance);
		}).to.throw("Expected object of a type with the GitSource trait, got an instance of SomeType instead");
	});

	it(" ... even if that type has an otherwise compatible-looking method", () => {
		let SomeOtherType = dm.createType("SomeOtherType", {
			value: dm.string(),
			stringify: dm.function([], dm.string())
		});

		let instance = SomeOtherType({
			value: "foo",
			stringify: dm.guard([], dm.string(), function () {
				return "this is not a URL at all";
			})
		});

		expect(() => {
			guardedFunc(instance);
		}).to.throw("Expected object of a type with the GitSource trait, got an instance of SomeOtherType instead");
	});

	it("should reject a trait implementation that does not meet the trait definition", () => {
		expect(() => {
			let InvalidType = dm.createType("InvalidType", {
				value: dm.string()
			}).implements(GitSource, {
				stringify: "this is not a function"
			});
		}).to.throw("Expected a guarded function () → string, got a string instead");
	});

	it("should reject an empty trait implementation when the trait definition does not allow that", () => {
		expect(() => {
			let InvalidType = dm.createType("InvalidType", {
				value: dm.string()
			}).implements(GitSource, {

			});
		}).to.throw("Value is required for property 'stringify'");
	});

	it("should allow for specifying slot rules", () => {
		ExternalGitSource = dm.createType("ExternalGitSource", {
			sourceName: dm.string()
		}).implements(GitSource, {
			stringify: dm.slot()
		});
	});

	it("should allow specifying a value for that slot", () => {
		randomGitSource = ExternalGitSource({
			sourceName: "randomGit",
			stringify: dm.guard([], dm.string(), function () {
				return "https://randomgit.example.com/repo.git"
			})
		});
	});

	it("should have produced a working slot value", () => {
		expect(randomGitSource.stringify()).to.equal("https://randomgit.example.com/repo.git");
	});

	it("should reject an invalid slot value in the instance", () => {
		expect(() => {
			ExternalGitSource({
				sourceName: "randomGit",
				stringify: "foo"
			});
		}).to.throw("Expected a guarded function () → string, got a string instead");
	});
});