test: add playground tests

Author: atheck

src/Testing/playground.spec.tsx

@@ -0,0 +1,86 @@
+import { render, type RenderResult } from "@testing-library/react";
+import type { JSX } from "react";
+import { errorHandler, errorMsg, type ErrorMessage } from "../ErrorHandling";
+import type { InitResult, UpdateMap } from "../Types";
+import { useElmish } from "../useElmish";
+import { getCreateUpdateArgs } from "./getCreateUpdateArgs";
+import { getUpdateFn } from "./getUpdateFn";
+import { renderWithModel } from "./renderWithModel";
+
+interface Model {
+	value1: string;
+	value2: string;
+	subPage: string;
+}
+
+interface Props {}
+
+type Message = { name: "doubleDefer" } | ErrorMessage;
+
+const Msg = {
+	doubleDefer: (): Message => ({ name: "doubleDefer" }),
+	...errorMsg,
+};
+
+function init(): InitResult<Model, Message> {
+	return [
+		{
+			value1: "",
+			value2: "",
+			subPage: "",
+		},
+	];
+}
+
+const update: UpdateMap<Props, Model, Message> = {
+	doubleDefer(_msg, _model, _props, { defer }) {
+		defer({ value2: "deferred" });
+		defer({ subPage: "subPage" });
+
+		return [{ value1: "computed" }];
+	},
+
+	...errorHandler(),
+};
+
+function Playground(props: Props): JSX.Element {
+	const [, dispatch] = useElmish({ name: "Playground", init, update, props });
+
+	return (
+		<div>
+			<button type={"button"} onClick={() => dispatch(Msg.doubleDefer())}>
+				{"Compute"}
+			</button>
+		</div>
+	);
+}
+
+function renderPlayground(modelTemplate?: Partial<Model>): RenderResult {
+	const model = {
+		...init()[0],
+		...modelTemplate,
+	};
+
+	return renderWithModel(() => render(<Playground />), model);
+}
+
+const getUpdateArgs = getCreateUpdateArgs(init, () => ({}));
+const updateFn = getUpdateFn(update);
+
+describe("Playground", () => {
+	it("renders without crashing", () => {
+		const { container } = renderPlayground();
+
+		expect(container).toBeTruthy();
+	});
+
+	describe("doubleDefer", () => {
+		it("computes the values", async () => {
+			const args = getUpdateArgs(Msg.doubleDefer());
+
+			const [model] = updateFn(...args);
+
+			expect(model).toStrictEqual({ value1: "computed", value2: "deferred", subPage: "subPage" });
+		});
+	});
+});