· breml

Wieso env var

better compatibility with most ide, because in most cases support for build tags is not great and they can confuse auto suggestion, etc.
also other static code analysis tools like linters might have problems or not able to process the integration test files
better usage of build cache, no need to recompile packages
compatible with ./…
possible to have unit tests and integration tests in the same test file
simple concept already used in other places for configuration, nothing new to learn
better compatibility with other test wrappers like go-acc for measuring coverage.
through the usage of t.skip, the test might give a hint to the user in verbose mode, how to execute the integration tests.
maybe combine with -short flag