chore: fix codecov (#11)

.gitignore

@@ -1,3 +1,4 @@
 coverage/
 lib/
 node_modules/
+.DS_Store

src/extend/temporal.test.ts

@@ -18,6 +18,7 @@ const instant: TsonType<Temporal.Instant, string> = {
 };
 
 const tson = createTson({
+	nonce: () => "__tson",
 	types: [plainDate, instant],
 });
 test("PlainDate", () => {

src/handlers/tsonUnknownObjectGuard.ts

@@ -1,5 +1,5 @@
+import { isPlainObject } from "../isPlainObject.js";
 import { TsonType } from "../types.js";
-import { isPlainObject } from "../utils.js";
 
 export class UnknownObjectGuardError extends Error {
 	/**

src/isPlainObject.test.ts

@@ -0,0 +1,31 @@
+import { expect, test } from "vitest";
+
+import { isPlainObject } from "./isPlainObject.js";
+
+test("should return true for plain objects", () => {
+	expect(isPlainObject({})).toBe(true);
+	expect(isPlainObject({ a: 1 })).toBe(true);
+	expect(isPlainObject(Object.create(null))).toBe(true);
+});
+
+test("should return false for non-objects", () => {
+	expect(isPlainObject(null)).toBe(false);
+	expect(isPlainObject(undefined)).toBe(false);
+	expect(isPlainObject(42)).toBe(false);
+	expect(isPlainObject("foo")).toBe(false);
+	expect(isPlainObject(true)).toBe(false);
+	expect(isPlainObject(Symbol())).toBe(false);
+});
+
+test("should return false for non-plain objects", () => {
+	expect(isPlainObject([])).toBe(false);
+	expect(isPlainObject(new Date())).toBe(false);
+	expect(isPlainObject(/foo/)).toBe(false);
+	expect(
+		isPlainObject(() => {
+			// noop
+		}),
+	).toBe(false);
+
+	expect(isPlainObject(Object.prototype)).toBe(false);
+});

src/tson.test.ts

@@ -0,0 +1,33 @@
+import { expect, test } from "vitest";
+
+import { createTson } from "./tson.js";
+import { TsonType } from "./types.js";
+
+test("multiple handlers for primitive string found", () => {
+	const stringHandler: TsonType<string, never> = {
+		primitive: "string",
+	};
+	expect(() => {
+		createTson({
+			types: [stringHandler, stringHandler],
+		});
+	}).toThrowErrorMatchingInlineSnapshot(
+		'"Multiple handlers for primitive string found"',
+	);
+});
+
+test("duplicate keys", () => {
+	const stringHandler: TsonType<string, string> = {
+		deserialize: (v) => v,
+		key: "string",
+		serialize: (v) => v,
+		test: (v) => typeof v === "string",
+	};
+	expect(() => {
+		createTson({
+			types: [stringHandler, stringHandler],
+		});
+	}).toThrowErrorMatchingInlineSnapshot(
+		'"Multiple handlers for key string found"',
+	);
+});

src/tson.ts

@@ -1,5 +1,6 @@
-// eslint-disable-next-line eslint-comments/disable-enable-pair
+/* eslint-disable eslint-comments/disable-enable-pair */
 /* eslint-disable @typescript-eslint/no-explicit-any */
+import { isPlainObject } from "./isPlainObject.js";
 import {
 	TsonAllTypes,
 	TsonDeserializeFn,
@@ -16,7 +17,6 @@ import {
 	TsonTypeTesterCustom,
 	TsonTypeTesterPrimitive,
 } from "./types.js";
-import { isPlainObject } from "./utils.js";
 
 function isTsonTuple(v: unknown, nonce: string): v is TsonTuple {
 	return Array.isArray(v) && v.length === 3 && v[2] === nonce;