Why does my HUnit test suite pass when my tests fail?

If I have test/Test.hs with

module Main where

import Test.HUnit

test1 :: Test
test1 = TestCase $ assertEqual "Should be one" 1 5

test2 :: Test
test2 = TestCase $ assertEqual "Shold both be zero" 0 0

main :: IO Counts
main = runTestTT $ TestList [test1, test2, test1]

and a .cabal with

test-suite my-test
    type:               exitcode-stdio-1.0
    hs-source-dirs:     test
    main-is:            Test.hs
    build-depends:      base >= 4.8.1.0 && <4.9,
                        HUnit >= 1.3
    default-language:   Haskell2010

and I run cabal test --show-details='always' then I get

Test suite my-test: RUNNING...
### Failure in: 0
test/Test.hs:6
Should be one
expected: 1
 but got: 5
### Failure in: 2
test/Test.hs:6
Should be one
expected: 1
 but got: 5
Cases: 3  Tried: 3  Errors: 0  Failures: 2
Test suite my-test: PASS

Why does my test suite pass when I've had failures? Likewise, if I cabal sdist I get no warning that my tests have failed.