add tests

package.json

@@ -16,6 +16,7 @@
     "license": "AGPL-3.0-only",
     "devDependencies": {
         "@types/cross-spawn": "^6.0.2",
+        "@types/jest": "^26.0.9",
         "@types/node": "^14.0.27",
         "@typescript-eslint/eslint-plugin": "^3.8.0",
         "@typescript-eslint/parser": "^3.8.0",
@@ -36,4 +37,4 @@
         "fs-extra": "^9.0.1",
         "yargs": "^15.4.1"
     }
-}
+}