How to write a config for travis ci?

Question

Node.js

How to correctly write a config for the following behavior:
Any commit or PR triggers tests npm run tests
If something with the tag tag is pushed to the master branch Run tests, build, deploy to production with a command , and deploy to npm run deployGitHub Releases
run twice with one different environment variable. BROWSER
That is, as I see it:
I commit to any branch - two parallel tests run
BROWSER=chrome npm run tests
BROWSER=firefox npm run tests
Someone makes a PR to any branch - two parallel tests run
BROWSER=chrome npm run tests
BROWSER=firefox npm run tests
I commit to the master with a tag - runs two parallel tests
BROWSER=chrome npm run tests
BROWSER=firefox npm run tests
If both tests pass, two commands are launched to deploy
BROWSER=chrome npm run deploy
BROWSER=firefox npm run deploy
AND the third command is to create a release on GitHub
I am not familiar with this tool at all. Wrote this config

language: node_js

node_js: 
  - "10"

env: 
  - BROWSER=chrome
  - BROWSER=firefox


script: npm run build

deploy:
  skip_cleanup: true
  provider: script
  script: npm run deploy
  on:
    branch: master

But it is not clear:
How to add a preliminary stage of testing here?
How to make deploy run only if there is a tag?
How will the task react to PR in the master branch?
How to add another task to deploy to GitHub?

Answer 1

Look at https://docs.travis-ci.com/user/build-stages/.
As far as I understand, you should have stages:
- test (with two browsers)
- build
- deploy (only if branch=master)