Tests present errors about types, inconsistently about svelte-jester HOT 1 CLOSED

I'm a bit late but maybe it can help someone else who is struggling on this like me. I had the same issue (except that the errors for me were consistent) and tried following the steps TypeScript was writing, adding jest to types. However after adding it, I had another error regarding svelte and saw that the base tsconfig (the one that is extended from @tsconfig/svelte/tsconfig.json) had svelte to the types array, so I needed to specify both jest and svelte, like this:

{
  "extends": "@tsconfig/svelte/tsconfig.json",
  "compilerOptions": {
    "types": ["jest", "svelte"]
  },

  "include": ["src/**/*"],
  "exclude": ["node_modules/*", "__sapper__/*", "public/*"]
}

After looking at your tsconfig.json and saw that you didn't specify the types option. I would recommend trying adding this and see if this helps. I can't really explain the inconsistent errors but hopefully the errors will be consistently gone for you after adding this option.

from svelte-jester.