CHANGELOG.md

 # html-validate changelog
 
+### [4.13.1](https://gitlab.com/html-validate/html-validate/compare/v4.13.0...v4.13.1) (2021-05-28)
+
+### Bug Fixes
+
+- **jest:** fix `TypeError: diff is not a function` ([2afc2e8](https://gitlab.com/html-validate/html-validate/commit/2afc2e8796d9e2a8b9b79af91625f6d844860a53))
+
 ## [4.13.0](https://gitlab.com/html-validate/html-validate/compare/v4.12.0...v4.13.0) (2021-05-28)
 
 ### Features

package-lock.json

 {
   "name": "html-validate",
-  "version": "4.13.0",
+  "version": "4.13.1",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
-      "version": "4.13.0",
+      "version": "4.13.1",
       "license": "MIT",
       "dependencies": {
         "@babel/code-frame": "^7.10.0",

package.json

 {
   "name": "html-validate",
-  "version": "4.13.0",
+  "version": "4.13.1",
   "description": "html linter",
   "keywords": [
     "html",

src/matchers.ts

 /* eslint-disable @typescript-eslint/no-namespace, @typescript-eslint/ban-ts-comment, prefer-template, sonarjs/no-duplicate-string */
 
-import * as jestDiff from "jest-diff";
+import jestDiffDefault, * as jestDiff from "jest-diff";
 import deepmerge from "deepmerge";
 import { TokenType } from "./lexer";
 import { Message, Report, Result } from "./reporter";
@@ -14,7 +14,8 @@ interface TokenMatcher {
 }
 
 /* istanbul ignore next: covered by compatibility tests but not a single pass */
-const diff = jestDiff?.diff ?? jestDiff;
+/* @ts-ignore typing for compatibility so it will seem "impossible" but different version will yield different source */
+const diff: typeof jestDiff.diff = jestDiffDefault ?? jestDiff?.diff ?? jestDiff;
 
 declare global {
 	namespace jest {