Allow for and in script of test

Script is here a file that isn't a svelte component
Configuring tsconfig.js might not be compulsory

jest.config.js

@@ -2,6 +2,25 @@
 
 //https://kulshekhar.github.io/ts-jest/docs/getting-started/installation
 export default {
-  preset: "ts-jest",
+  globals: {
+    "ts-jest": {
+      useESM: true,
+    },
+  },
+  moduleNameMapper: {
+    //"\\$lib/(.+)$": "<rootDir>/src/lib/$1",
+    //"\\$app/(.+)$": "<rootDir>/.svelte-kit/dev/runtime/app/$1",
+    //"^\\$lib(.*)$": "<rootDir>/src/lib$1",
+    //"^\\$app(.*)$": "<rootDir>/.svelte-kit/dev/runtime/app$1",
+
+    "^\\$lib(.*)$": "<rootDir>/src/lib$1",
+    "^\\$app(.*)$": [
+      "<rootDir>/.svelte-kit/dev/runtime/app$1",
+      "<rootDir>/.svelte-kit/build/runtime/app$1",
+    ],
+  },
+  //https://kulshekhar.github.io/ts-jest/docs/guides/esm-support/
+  //preset: "ts-jest",
+  preset: "ts-jest/presets/default-esm",
   testEnvironment: "node",
 }

tsconfig.json

@@ -27,5 +27,19 @@
       "$lib/*": ["src/lib/*"]
     }
   },
-  "include": ["src/**/*.d.ts", "src/**/*.js", "src/**/*.ts", "src/**/*.svelte"]
+  "include": ["src/**/*.d.ts", "src/**/*.js", "src/**/*.ts", "src/**/*.svelte"],
+  /**
+    Setting a name mapper allow Jest tests written in TypeScript to know about $lib and $app.
+    */
+  "moduleNameMapper": {
+    //"\\$lib/(.+)$": "<rootDir>/src/lib/$1",
+    //"\\$app/(.+)$": "<rootDir>/.svelte-kit/dev/runtime/app/$1",
+    //"^\\$lib(.*)$": "<rootDir>/src/lib$1",
+    //"^\\$app(.*)$": "<rootDir>/.svelte-kit/dev/runtime/app$1",
+    "^\\$lib(.*)$": "<rootDir>/src/lib$1",
+    "^\\$app(.*)$": [
+      "<rootDir>/.svelte-kit/dev/runtime/app$1",
+      "<rootDir>/.svelte-kit/build/runtime/app$1",
+    ],
+  },
 }