Fizzbuzz in Haskell using guards

fizzbuzz.hs

import Test.HUnit

fizzbuzz :: Int -> String
fizzbuzz x
         | x `mod` 15 == 0 = "fizzbuzz"
         | x `mod` 3 == 0 = "fizz"
         | x `mod` 5 == 0 = "buzz"
         | True = show x


test1 = TestCase (do assertEqual "" "1" (fizzbuzz 1))
test2 = TestCase (do assertEqual "" "fizz" (fizzbuzz 3))
test3 = TestCase (do assertEqual "" "4" (fizzbuzz 4))
test4 = TestCase (do assertEqual "" "buzz" (fizzbuzz 5))
test5 = TestCase (do assertEqual "" "fizz" (fizzbuzz 6))
test6 = TestCase (do assertEqual "" "buzz" (fizzbuzz 10))
test7 = TestCase (do assertEqual "" "fizzbuzz" (fizzbuzz 15))

tests :: Test
tests = TestList [TestLabel "test1" test1,
                 TestLabel "test2" test2,
                 TestLabel "test3" test3,
                 TestLabel "test4" test4,
                 TestLabel "test5" test5,
                 TestLabel "test6" test6,
                 TestLabel "test7" test7]

main :: IO Counts
main = do runTestTT tests