Ruby 3.1 was released about a month ago, but it doesn’t appear to be available in Travis.
Here is the run: Travis CI - Test and Deploy with Confidence
This is what .travis.yml looks like:
"language": "ruby",
"os": [
"linux"
],
"dist": "focal",
"cache": {
"bundler": true
},
"before_install": [
"gem install bundler"
],
"rvm": [
"2.5.8",
"2.6.6",
"2.7.2",
"3.0.0",
"3.1.0"
],
"branches": {
"only": [
"master"
]
}
}