cabal test does not tail standard output of the running test executable

[fushunpoon]

Problem:

cabal test does not tail standard output of the running test executable. Instead, any output from the executable is output right at the end of the test process in one batch.

Motivation:

It is incredibly useful to have cabal test tail the stdout of the test executable currently being executed such that CI tools such as TeamCity? can be made to record the time it takes to run individual tests.

Reproduction:

Run the following simple executable as a test executable with cabal test --show-details=always

module Main where

import Control.Concurrent

delay = 5000000

main = do
  putStrLn "First message"
  threadDelay delay
  putStrLn "Second message"
  threadDelay delay
  putStrLn "Third message"
  threadDelay delay

Instead of outputting each line ("First/Second/Third message") five seconds after another, all three lines are output along with test result reporting all at once at the end of the test suite.