Using Istanbul With TypeScript & mocha

Thanks to @mohsen1's post the following is the minimum recommended configuration to get accurate TypeScript coverage with mocha. With this configuration, the all: true and cache: true options should work.

You will also need to npm install --save-dev source-map-support, which will also require that you have sourcemaps configured in your tsconfig.json. Inline, or not, as long as one is enabled.


  "scripts": {
    "test": "nyc mocha"
  "nyc": {
    "extension": [
    "exclude": [
    "reporter": [
    "all": true  


--require ts-node/register # replace with ts-node/register/transpile-only if you have custom types
--require source-map-support/register
<glob for your test files>

If you're having trouble, try looking at the existing TypeScript issues for troubleshooting steps.