You can check your code for Sylius coding standard by running the following command:
vendor/bin/ecschecksrctests
Some of the violations can be automatically fixed by running the same command with --fix suffix like:
vendor/bin/ecschecksrctests--fix
Most of Sylius coding standard checks are extracted to SyliusLabs/CodingStandard package so that reusing them in your own projects or Sylius plugins is effortless. To learn about details, take a look at its README.