travis does not generate coverage for a project node

I'm practicing data structures in typescript and in my place I get the coverage report without problems

but in travis-ci it does not appear to me.

Will there be any configuration problems with node or a travis own problem?

It's my third project with typescript, so I can not tell the difference.

Additional information:

• Project code
• Travis Complete Trace
• package.json

{
  "name": "datastructurestypescript",
  "version": "0.0.1",
  "private": false,
  "scripts": {
    "pretest": "nyc mocha -r ts-node/register public/tests/**/*.ts",
    "test": "nyc report --reporter=json",
    "posttest": "codecov -f coverage/*.json -t b8b6c1c6-4dda-4fd4-8298-443e08034f2c"
  },
  "repository": {
    "type": "git",
    "url": "https://github.com/javatlacati/datastructurestypescript.git"
  },
  "devDependencies": {
    "chai": "^4.1.2",
    "mocha": "^4.0.1",
    "ts-node": "^3.3.0",
    "@types/npm": "^2.0.29",
    "nyc": "^11.4.1",
    "codecov": "^1.0.1"
  },
  "main": "dist/index",
  "typings": "dist/index",
  "author": "RUSLAN LOPEZ",
  "license": "LGPL-3.0-or-later"
}

• travis-yml

dist: trusty
sudo: false
language: node_js

node_js:
  - node
#  - lts/* # safety net; don't remove
#  - node # safety net; don't remove
before_script:
  - npm install typescript
  - npm install @types/chai
  - npm install @types/mocha