message: test isPlainObject util
diff: import { assertEquals as equals } from "../deps/assert.ts";
  -import { merge, searchByExtension } from "../core/utils.ts";
  +import { isPlainObject, merge, searchByExtension } from "../core/utils.ts";
  Deno.test("merge options", () => {
  interface Options {
  @@ -75,3 +75,12 @@ Deno.test("search by extension", () => {
  equals(searchByExtension(".ts", extensions), [".ts", "ts"]);
  equals(searchByExtension("foo", extensions), undefined);
  });
  +
  +Deno.test("isPlainObject", () => {
  + equals(isPlainObject({}), true);
  + equals(isPlainObject(new URL("http://localhost")), false);
  + equals(isPlainObject([]), false);
  + equals(isPlainObject(new Map()), false);
  + equals(isPlainObject(new Set()), false);
  + equals(isPlainObject(Symbol.for("foo")), false);
  +});
  