Upgrade to new major version 26 of Jest

package.json

@@ -30,13 +30,13 @@
     "@typescript-eslint/parser": "^2.34.0",
     "eslint": "^7.1.0",
     "husky": "^4.2.5",
-    "jest": "^25.5.4",
+    "jest": "^26.0.1",
     "lint-staged": "^10.2.6",
     "prettier": "2.0.5",
     "rdf-namespaces": "^1.8.0",
     "rollup": "^2.10.9",
     "rollup-plugin-typescript2": "^0.27.1",
-    "ts-jest": "^25.5.1",
+    "ts-jest": "^26.0.0",
     "typescript": "^3.9.3"
   },
   "dependencies": {

src/datatypes.test.ts

@@ -1,3 +1,4 @@
+import { describe, it, expect } from "@jest/globals";
 import { DataFactory } from "n3";
 import { LocalNode } from "./index";
 import {

src/fetcher.test.ts

@@ -1,9 +1,13 @@
+import { it, expect } from "@jest/globals";
 jest.mock("cross-fetch");
 
 import { fetch } from "./fetcher";
 
 it("should fallback to cross-fetch if no Solid-specific fetcher is available", async () => {
-  const crossFetch = jest.requireMock("cross-fetch");
+  const crossFetch = jest.requireMock("cross-fetch") as jest.Mock<
+    ReturnType<typeof window.fetch>,
+    [RequestInfo, RequestInit]
+  >;
 
   await fetch("https://some.url");