testpackage is a golang linter that makes you use a separate _test package.

According to blackbox testing approach, you should not use unexported functions and methods from source code in tests.

Go allows to place tests in a separate package with suffix _test. For example, tests for store package can be in the same package or in the package store_test. In the second case, you have to import the source code into tests so only exported things are available.

The linter reports if a test is in a package without suffix _test. If you really need to test unexported function, then put the test into file XXX_internal_test.go. The linter skips such files by default. It also skips the file export_test.go by default (see the last article below).

More detailed articles on this topic:

• Next level Go testing by Tit Petric
• 5 simple tips and tricks for writing unit tests in #golang by Mat Ryer
• 5 advanced testing techniques in Go by Alan Braithwaite
• Golang Trick: Export unexport method for test by lysu

The best way is to use golangci-lint. It includes testpackage linter started from v1.25.0 and higher.

See install section of readme.

testpackage is disabled by default. To enable it, add the following to your .golangci.yml:

linters:
  enable:
    testpackage

You can also change regexp that is used to ignore files by the linter. Here is the default value.

linters-settings:
  testpackage:
    skip-regexp: (export|internal)_test\.go

golangci-lint run

go get -u github.com/maratori/testpackage

testpackage ./...

or

testpackage -skip-regexp="^$" ./...

testpackage -help

testpackage: linter that makes you use a separate _test package

Usage: testpackage [-flag] [package]

Flags:  -V      print version and exit
  -skip-regexp string
        regexp pattern to skip file by name. To not skip files use -skip-regexp="^$" (default "(export|internal)_test\\.go")
  -json
        emit JSON output
  -c int
        display offending line with this many lines of context (default -1)
  -cpuprofile string
        write CPU profile to this file
  -memprofile string
        write memory profile to this file

• No changes in linter behavior
• Use latest go version on travis-ci
• Update Makefile
• Update golangci-lint

• Go Analyzer to check the name of test package
• main.go to run the analyzer
• MIT license