Create and run a minimal test suite in Haskell using Hunit only

Question

I'm relatively new to Haskell, so apologies in advance if my terminology is not quite correct.

I would like to implement some plain unit test for a very simple project, managed through cabal. I noticed this very similar question, but it didn't really help. This one didn't either (and it mentions tasty, see below).

I think I can accomplish this by using only HUnit - however, I admit I am a bit confused by all other "things" that guides on the net talk about:

• I don't quite appreciate the difference between the interfaces exitcode-stdio-1.0 and detailed-0.9
• I am not sure about the differences (or mid- and long-terms) implication of using HUnit or Quickcheck or others?
• What's the role of tasty that the HUnit guide mentions.

So, I tried to leave all "additional" packages out of the equation and everything else as "default" as much as I could aside and did the following:

$ mkdir example ; mkdir example/test
$ cd example
$ cabal init

Then edited example.cabal and added this section:

Test-Suite test-example
    type:             exitcode-stdio-1.0
    hs-source-dirs:   test, app
    main-is:          Main.hs
    build-depends:    base >=4.15.1.0,
                      HUnit
    default-language: Haskell2010

Then I created test/Main.hs with this content:

module Main where

import Test.HUnit

tests = TestList [
    TestLabel "test2"
        (TestCase $ assertBool "Why is this not running," False)
                 ]

main :: IO ()
main = do
    runTestTT tests
    return ()

Finally, I tried to run the whole lot:

$ cabal configure --enable-tests && cabal build && cabal test
Up to date
Build profile: -w ghc-9.2.4 -O1
In order, the following will be built (use -v for more details):
 - example-0.1.0.0 (test:test-example) (additional components to build)
Preprocessing test suite 'test-example' for example-0.1.0.0..
Building test suite 'test-example' for example-0.1.0.0..
Build profile: -w ghc-9.2.4 -O1
In order, the following will be built (use -v for more details):
 - example-0.1.0.0 (test:test-example) (ephemeral targets)
Preprocessing test suite 'test-example' for example-0.1.0.0..
Building test suite 'test-example' for example-0.1.0.0..
Running 1 test suites...
Test suite test-example: RUNNING...
Test suite test-example: PASS
Test suite logged to:
/home/jir/workinprogress/haskell/example/dist-newstyle/build/x86_64-linux/ghc-9.2.4/example-0.1.0.0/t/test-example/test/example-0.1.0.0-test-example.log
1 of 1 test suites (1 of 1 test cases) passed.

And the output is not what I expected. I'm clearly doing something fundamentally wrong, but I don't know what it is.

Answer 1

In order for the exitcode-stdio-1.0 test type to recognize a failed suite, you need to arrange for your test suite's main function to exit with failure in case there are any test failures. Fortunately, there's a runTestTTAndExit function to handle this, so if you replace your main with:

main = runTestTTAndExit tests

it should work fine.