如何打包golang测试助手代码？

Question

I have some test helper code in my golang library that I want to use when testing in various subpackages. However, I've hit a snag:

outer
|
+- test_helpers_test.go
|
+- inner
   |
   +- something.go
   +- something_test.go

To use the code in test_helpers_test.go, I have to import the outer package. But when I import the outer package from something_test.go, it complains "import cycle not allowed in test"

So I tried making a package for the shared test helpers:

outer
|
+- test
|  |
|  +- test_helpers_test.go
|
+- inner
   |
   +- something.go
   +- something_test.go

And now it complains "no non-test Go files in /home/karl/Projects/outer/test"

I don't want to call it test_helpers.go because it's part of my testing code, not my library code. I don't want to ship that code in the library.

How do I solve this?

---

Update: I can work around the issue by creating a dummy.go file in the test directory, but now there's a new problem: Importing a package DOESN'T import its test code! So now I get: ./something_test.go:12:2: undefined: test.AssertDoesPanic

Answer 1

Following go issue 8279, I have seen dummy files added, as in tommie/acme-cli commit 479f8c7

outer/outer.go

// +build ignore+
package outer

See if that could help here, as a workaround.

---

As commented above, using a test helper code in an internal package (from Go 1.4+) is another option, since no client from this project would be able to access said helper. See design document.
You can see it used in a typical Go project layout.