Could not find module ‘Test.HUnit’

Question

I have a fresh installation of stack and ghci:

$ stack --version

Version 1.6.3, Git revision b27e629b8c4ce369e3b8273f04db193b060000db (5454 commits) x86_64 hpack-0.20.0

$ ghci --version

The Glorious Glasgow Haskell Compilation System, version 8.2.1

I make a new project:

$ stack new so-mve

Downloading template "new-template" to create project "so-mve" in so-mve/ 
... blah blah blah ...
Looking for .cabal or package.yaml files to use to init the project.
Using cabal packages:
- so-mve/
Selecting the best among 12 snapshots...
* Matches lts-10.3
Selected resolver: lts-10.3
Initialising configuration using resolver: lts-10.3
Total number of user packages considered: 1
Writing configuration to file: so-mve/stack.yaml
All done.

Looks pretty good:

$ tree so-mve

so-mve
├── ChangeLog.md
├── LICENSE
├── README.md
├── Setup.hs
├── app
│   └── Main.hs
├── package.yaml
├── so-mve.cabal
├── src
│   └── Lib.hs
├── stack.yaml
└── test
    └── Spec.hs

It builds and runs:

$ cd so-mve
$ stack build

so-mve-0.1.0.0: build (lib + exe)
Preprocessing library for so-mve-0.1.0.0..
Building library for so-mve-0.1.0.0..
Preprocessing executable 'so-mve-exe' for so-mve-0.1.0.0..
Building executable 'so-mve-exe' for so-mve-0.1.0.0..
so-mve-0.1.0.0: copy/register
Installing library in /...blah-blah.../so-mve/.stack-work/install/x86_64-osx/lts-10.3/8.2.2/lib/x86_64-osx-ghc-8.2.2/so-mve-0.1.0.0-5kG2WnHWwo99IiYYGoxrcC
Installing executable so-mve-exe in /...blah-blah.../so-mve/.stack-work/install/x86_64-osx/lts-10.3/8.2.2/bin
Registering library for so-mve-0.1.0.0..

$ stack exec so-mve-exe

someFunc

Tests run:

$ stack test

blah blah blah
[2 of 2] Compiling Main             ( test/Spec.hs, .stack-work/dist/x86_64-osx/Cabal-2.0.1.0/build/so-mve-test/so-mve-test-tmp/Main.o )
...blah-blah-blah...
Progress: 1/2Test suite not yet implemented
so-mve-0.1.0.0: Test suite so-mve-test passed
Completed 2 action(s).

I triple check that HUnit is installed

$ stack install HUnit

Populated index cache.

I add one line to test/Spec.hs

$ cat test/Spec.hs

import Test.HUnit
main :: IO ()
main = putStrLn "Test suite not yet implemented"

Doesn't work:

$ stack test

so-mve-0.1.0.0: unregistering (components added: test:so-mve-test)
so-mve-0.1.0.0: build (lib + exe + test)
Preprocessing library for so-mve-0.1.0.0..
Building library for so-mve-0.1.0.0..
Preprocessing executable 'so-mve-exe' for so-mve-0.1.0.0..
Building executable 'so-mve-exe' for so-mve-0.1.0.0..
Preprocessing test suite 'so-mve-test' for so-mve-0.1.0.0..
Building test suite 'so-mve-test' for so-mve-0.1.0.0..
[2 of 2] Compiling Main             ( test/Spec.hs, .stack-work/dist/x86_64-osx/Cabal-2.0.1.0/build/so-mve-test/so-mve-test-tmp/Main.o )

/...blah-blah.../so-mve/test/Spec.hs:1:1: error:
    Could not find module ‘Test.HUnit’
    Use -v to see a list of the files searched for.
  |          
1 | import Test.HUnit
  | ^^^^^^^^^^^^^^^^^

Progress: 1/2
--  While building custom Setup.hs for package so-mve-0.1.0.0 using:
      /Users/XXXXXXXX/.stack/setup-exe-cache/x86_64-osx/Cabal-simple_mPHDZzAJ_2.0.1.0_ghc-8.2.2 --builddir=.stack-work/dist/x86_64-osx/Cabal-2.0.1.0 build lib:so-mve exe:so-mve-exe test:so-mve-test --ghc-options " -ddump-hi -ddump-to-file -fdiagnostics-color=always"
    Process exited with code: ExitFailure 1

I don't have trouble importing other libraries, like Text.Read and Text.Printf. I googled around a bunch, but didn't find an answer. Any ideas for me?

Answer 1

You just need to add HUnit to the dependencies for your test project. When using stack, you should edit the package.yaml file to specify dependencies. In particular, your test configuration should look something like:

tests:
  so-mve-test:
    main:                Spec.hs
    source-dirs:         test
    ghc-options:
    - ...
    dependencies:
    - HUnit

This is documented in the latest Stack Guide, under the section Adding Dependencies.

Answer 2

You installed HUnit globally with stack, but that doesn't mean it is specified for your project.

Your cabal file for the project needs to specify a dependency on HUnit:

--so-mve.cabal
...
test-suite so-mve 
  type:                exitcode-stdio-1.0
  hs-source-dirs:      test
  main-is:             Spec.hs
  build-depends:       base
                     , HUnit
  ...

Text.Read and Text.Printf are both included in base, so you don't need to specify an additional dependency.

---

As pointed out in the comments, since you're using a package.yaml (as opposed to a stack.yaml) configuration with the newer version of stack, you'll need to specify the dependency there instead of the .cabal file:

tests:
  so-mve-test:
    main: Spec.hs
    source-dirs: test
    ghc-options:
    - -threaded
    dependencies:
    - HUnit