Add tests for the Handlebars helper equal

client/js/libs/handlebars/equal.js

@@ -1,8 +1,13 @@
 "use strict";
 
 module.exports = function(a, b, opt) {
+	if (arguments.length !== 3) {
+		throw new Error("Handlebars helper `equal` expects 3 arguments");
+	}
+
 	a = a.toString();
 	b = b.toString();
+
 	if (a === b) {
 		return opt.fn(this);
 	}

test/client/js/libs/handlebars/equalTest.js

@@ -0,0 +1,26 @@
+"use strict";
+
+const expect = require("chai").expect;
+const equal = require("../../../../../client/js/libs/handlebars/equal");
+
+describe("equal Handlebars helper", function() {
+	const block = {
+		fn: () => "fn",
+		inverse: () => "inverse",
+	};
+
+	it("should render the first block if both values are equal", function() {
+		expect(equal("foo", "foo", block)).to.equal("fn");
+	});
+
+	it("should render the inverse block if values are not equal", function() {
+		expect(equal("foo", "bar", block)).to.equal("inverse");
+	});
+
+	it("should throw if too few or too many arguments are given", function() {
+		expect(() => equal("foo", block)).to.throw(Error, /expects 3 arguments/);
+
+		expect(() => equal("foo", "bar", "baz", block))
+			.to.throw(Error, /expects 3 arguments/);
+	});
+});