Test.Main

Utilities for testing your main function

captureProcessResult :: IO () -> IO ProcessResult

Capture stdout, stderr, and exit code of the given IO action.

>>> let main = putStr "hello"
>>> captureProcessResult main
ProcessResult {prStdout = "hello", prStderr = "", prExitCode = ExitSuccess, prException = Nothing}

If the IO action exit with error message, the exit code of result is ExitFailure.

>>> import System.IO
>>> import System.Exit
>>> let main = hPutStr stderr "OMG!" >> exitWith (ExitFailure 1)
>>> captureProcessResult main
ProcessResult {prStdout = "", prStderr = "OMG!", prExitCode = ExitFailure 1, prException = Nothing}

Since v0.2.0.0, this function catches SomeException, not only ExitCode to prevent it from losing output when an exception other than ExitCode is thrown. To get the thrown error, use prException.

Note: prStderr doesn't contain the error message of the thrown exception. See the example below.

>>> import Control.Exception
>>> let main = ioError $ userError "OMG!"
>>> captureProcessResult main
ProcessResult {prStdout = "", prStderr = "", prExitCode = ExitFailure 1, prException = Just user error (OMG!)}

Since: 0.2.0.0

data ProcessResult

Used for the result of captureProcessResult.

Constructors

ProcessResult

Fields

• prStdout :: !ByteString
• prStderr :: !ByteString
• prExitCode :: !ExitCode
• prException :: !(Maybe SomeException)

Instances

Eq ProcessResult

Defined in Test.Main.Internal

Methods

(==) :: ProcessResult -> ProcessResult -> Bool

(/=) :: ProcessResult -> ProcessResult -> Bool

Show ProcessResult

Defined in Test.Main.Internal

Methods

showsPrec :: Int -> ProcessResult -> ShowS

show :: ProcessResult -> String

showList :: [ProcessResult] -> ShowS

Generic ProcessResult

Defined in Test.Main.Internal

Associated Types

type Rep ProcessResult :: Type -> Type

Methods

from :: ProcessResult -> Rep ProcessResult x

to :: Rep ProcessResult x -> ProcessResult

type Rep ProcessResult

Defined in Test.Main.Internal

type Rep ProcessResult = D1 (MetaData "ProcessResult" "Test.Main.Internal" "main-tester-0.2.0.1-ICm7aJKlueu6ZdSSOV6sNp" False) (C1 (MetaCons "ProcessResult" PrefixI True) ((S1 (MetaSel (Just "prStdout") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 ByteString) :*: S1 (MetaSel (Just "prStderr") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 ByteString)) :*: (S1 (MetaSel (Just "prExitCode") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 ExitCode) :*: S1 (MetaSel (Just "prException") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 (Maybe SomeException)))))

withStdin :: ByteString -> IO a -> IO a

Pass the ByteString to stdin of the given IO action.

>>> import Data.ByteString.Char8 ()
>>> :set -XOverloadedStrings
>>> let main = putStrLn . reverse =<< getLine
>>> withStdin "abcde" main
edcba

withEnv :: [(String, Maybe String)] -> IO a -> IO a

Run the given IO action with the specified environment variables set. The environment variables are specified as pairs of ENV_VAR_NAME and ENV_VAR_VALUE. If ENV_VAR_VALUE is Nothing, the ENV_VAR_NAME is unset with unsetEnv.

>>> import System.Environment
>>> setEnv "ENV_VAR_TO_UNSET"    "value_to_unset"
>>> setEnv "ENV_VAR_TO_OVERWRITE" "value_to_overwrite"
>>> let main = (print =<< lookupEnv "ENV_VAR_TO_UNSET") >> (print =<< lookupEnv "ENV_VAR_TO_OVERWRITE")
>>> withEnv [("ENV_VAR_TO_UNSET", Nothing), ("ENV_VAR_TO_OVERWRITE" , Just "new_value")] main
Nothing
Just "new_value"
>>> main
Just "value_to_unset"
Just "value_to_overwrite"

Re-export from System.Environment

withArgs :: [String] -> IO a -> IO a

withArgs args act - while executing action act, have getArgs return args.

Re-export from System.Exit

data ExitCode

Defines the exit codes that a program can return.

Constructors

ExitSuccess

indicates successful termination;

ExitFailure Int

indicates program failure with an exit code. The exact interpretation of the code is operating-system dependent. In particular, some values may be prohibited (e.g. 0 on a POSIX-compliant system).

Instances

Eq ExitCode

Defined in GHC.IO.Exception

Methods

(==) :: ExitCode -> ExitCode -> Bool

(/=) :: ExitCode -> ExitCode -> Bool

Ord ExitCode

Defined in GHC.IO.Exception

Methods

compare :: ExitCode -> ExitCode -> Ordering

(<) :: ExitCode -> ExitCode -> Bool

(<=) :: ExitCode -> ExitCode -> Bool

(>) :: ExitCode -> ExitCode -> Bool

(>=) :: ExitCode -> ExitCode -> Bool

max :: ExitCode -> ExitCode -> ExitCode

min :: ExitCode -> ExitCode -> ExitCode

Read ExitCode

Defined in GHC.IO.Exception

Methods

readsPrec :: Int -> ReadS ExitCode

readList :: ReadS [ExitCode]

readPrec :: ReadPrec ExitCode

readListPrec :: ReadPrec [ExitCode]

Show ExitCode

Defined in GHC.IO.Exception

Methods

showsPrec :: Int -> ExitCode -> ShowS

show :: ExitCode -> String

showList :: [ExitCode] -> ShowS

Generic ExitCode

Defined in GHC.IO.Exception

Associated Types

type Rep ExitCode :: Type -> Type

Methods

from :: ExitCode -> Rep ExitCode x

to :: Rep ExitCode x -> ExitCode

Exception ExitCode

Since: base-4.1.0.0

Defined in GHC.IO.Exception

Methods

toException :: ExitCode -> SomeException

fromException :: SomeException -> Maybe ExitCode

displayException :: ExitCode -> String

type Rep ExitCode

Defined in GHC.IO.Exception

type Rep ExitCode = D1 (MetaData "ExitCode" "GHC.IO.Exception" "base" False) (C1 (MetaCons "ExitSuccess" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "ExitFailure" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Int)))