Use custom Prelude based on relude.relude

The Prelude now longer exports partial functions, so
a large number of uses of these functions in the
code base have been rewritten.

A .ghci file has been added; this is necessary for
ghci to work properly with the custom Prelude.

Currently there are lots of compiler warnings.
We should either fix these or go to using a custom
Prelude that changes less than relude.

42 files changed, 237 insertions, 226 deletions

diff --git a/test/Tests/Command.hs b/test/Tests/Command.hs
index 59b04eac1..e3d9b636a 100644
--- a/test/Tests/Command.hs
+++ b/test/Tests/Command.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE TupleSections #-}
+{-# LANGUAGE OverloadedStrings #-}
 {- |
    Module      : Tests.Command
    Copyright   : © 2006-2021 John MacFarlane
@@ -35,8 +36,8 @@ import qualified Text.Pandoc.UTF8 as UTF8
 -- | Run a test with and return output.
 execTest :: String    -- ^ Path to test executable
          -> String    -- ^ Shell command
-         -> String    -- ^ Input text
-         -> IO (ExitCode, String)  -- ^ Exit code and actual output
+         -> Text    -- ^ Input text
+         -> IO (ExitCode, Text)  -- ^ Exit code and actual output
 execTest testExePath cmd inp = do
   mldpath   <- Env.lookupEnv "LD_LIBRARY_PATH"
   mdyldpath <- Env.lookupEnv "DYLD_LIBRARY_PATH"
@@ -48,9 +49,9 @@ execTest testExePath cmd inp = do
              maybe [] ((:[]) . ("LD_LIBRARY_PATH",)) mldpath ++
              maybe [] ((:[]) . ("DYLD_LIBRARY_PATH",)) mdyldpath
   let pr = (shell (pandocToEmulate True cmd)){ env = Just env' }
-  (ec, out', err') <- readCreateProcessWithExitCode pr inp
+  (ec, out', err') <- readCreateProcessWithExitCode pr (T.unpack inp)
   -- filter \r so the tests will work on Windows machines
-  let out = filter (/= '\r') $ err' ++ out'
+  let out = T.pack $ filter (/= '\r') $ err' ++ out'
   case ec of
     ExitFailure _ -> hPutStr stderr err'
     ExitSuccess   -> return ()
@@ -68,8 +69,8 @@ pandocToEmulate _ [] = []
 runTest :: String    -- ^ Path to test executable
         -> String    -- ^ Title of test
         -> String    -- ^ Shell command
-        -> String    -- ^ Input text
-        -> String    -- ^ Expected output
+        -> Text      -- ^ Input text
+        -> Text      -- ^ Expected output
         -> TestTree
 runTest testExePath testname cmd inp norm = testCase testname $ do
   (ec, out) <- execTest testExePath cmd inp
@@ -96,22 +97,23 @@ isCodeBlock :: Block -> Bool
 isCodeBlock (CodeBlock _ _) = True
 isCodeBlock _               = False
 
-extractCode :: Block -> String
-extractCode (CodeBlock _ code) = T.unpack code
+extractCode :: Block -> Text
+extractCode (CodeBlock _ code) = code
 extractCode _                  = ""
 
 dropPercent :: String -> String
 dropPercent ('%':xs) = dropWhile (== ' ') xs
 dropPercent xs       = xs
 
-runCommandTest :: FilePath -> FilePath -> Int -> String -> TestTree
+runCommandTest :: FilePath -> FilePath -> Int -> Text -> TestTree
 runCommandTest testExePath fp num code =
   goldenTest testname getExpected getActual compareValues updateGolden
  where
   testname = "#" <> show num
   codelines = lines code
-  (continuations, r1) = span ("\\" `isSuffixOf`) codelines
-  cmd = dropPercent (unwords (map init continuations ++ take 1 r1))
+  (continuations, r1) = span ("\\" `T.isSuffixOf`) codelines
+  cmd = dropPercent $ T.unpack $ T.unwords $
+          map (T.dropEnd 1) continuations ++ take 1 r1
   r2 = drop 1 r1
   (inplines, r3) = break (=="^D") r2
   normlines = takeWhile (/=".") (drop 1 r3)
@@ -123,14 +125,16 @@ runCommandTest testExePath fp num code =
     | actual == expected = return Nothing
     | otherwise = return $ Just $ "--- test/command/" ++ fp ++ "\n+++ " ++
                                 cmd ++ "\n" ++ showDiff (1,1)
-                                   (getDiff (lines actual) (lines expected))
+                                   (getDiff
+                                     (lines actual)
+                                     (lines expected))
   updateGolden newnorm = do
     let fp' = "command" </> fp
     raw <- UTF8.readFile fp'
-    let cmdline = "% " <> cmd
+    let cmdline = "% " <> T.pack cmd
     let x = cmdline <> "\n" <> input <> "^D\n" <> norm
     let y = cmdline <> "\n" <> input <> "^D\n" <> newnorm
-    let updated = T.replace (T.pack x) (T.pack y) raw
+    let updated = T.replace x y raw
     UTF8.writeFile fp' updated
 
 extractCommandTest :: FilePath -> FilePath -> TestTree
diff --git a/test/Tests/Helpers.hs b/test/Tests/Helpers.hs
index 64c2785ed..c8957a050 100644
--- a/test/Tests/Helpers.hs
+++ b/test/Tests/Helpers.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE OverloadedStrings    #-}
 {- |
    Module      : Tests.Helpers
    Copyright   : © 2006-2021 John MacFarlane
@@ -17,73 +18,77 @@ module Tests.Helpers ( test
                      , (=?>)
                      , purely
                      , ToString(..)
+                     , ToText(..)
                      , ToPandoc(..)
                      )
                      where
 
 import Data.Algorithm.Diff
 import qualified Data.Map as M
-import Data.Text (Text, unpack)
+import qualified Data.Text as T
 import System.Exit
 import Test.Tasty
 import Test.Tasty.HUnit
-import Text.Pandoc.Builder (Blocks, Inlines, doc, plain)
+import Text.Pandoc.Builder (Blocks, Inlines, doc, plain, nullMeta)
 import Text.Pandoc.Class
 import Text.Pandoc.Definition
 import Text.Pandoc.Options
 import Text.Pandoc.Shared (trimr)
 import Text.Pandoc.Writers.Native (writeNative)
 import Text.Printf
+import qualified GHC.Show
+import Prelude hiding (First)
 
-test :: (ToString a, ToString b, ToString c, HasCallStack)
+test :: (ToText a, ToText b, ToText c, HasCallStack)
      => (a -> b)  -- ^ function to test
      -> String    -- ^ name of test case
      -> (a, c)    -- ^ (input, expected value)
      -> TestTree
 test fn name (input, expected) =
-  testCase name' $ assertBool msg (actual' == expected')
-     where msg = nl ++ dashes "input" ++ nl ++ input' ++ nl ++
-                 dashes "result" ++ nl ++
-                 unlines (map vividize diff) ++
+  testCase name' $ assertBool (T.unpack msg) (actual' == expected')
+     where msg = nl <> dashes "input" <> nl <> input' <> nl <>
+                 dashes "result" <> nl <>
+                 T.unlines (map vividize diff) <>
                  dashes ""
            nl = "\n"
            name'   = if length name > 54
-                        then take 52 name ++ "..."  -- avoid wide output
+                        then Prelude.take 52 name ++ "..."  -- avoid wide output
                         else name
-           input'  = toString input
-           actual' = lines $ toString $ fn input
-           expected' = lines $ toString expected
+           input'  = toText input
+           actual' = T.lines $ toText $ fn input
+           expected' = T.lines $ toText expected
            diff = getDiff expected' actual'
-           dashes "" = replicate 72 '-'
-           dashes x  = replicate (72 - length x - 5) '-' ++ " " ++ x ++ " ---"
+           dashes "" = T.replicate 72 "-"
+           dashes x  = T.replicate (72 - T.length x - 5) "-" <>
+                        " " <> x <> " ---"
 
 data TestResult = TestPassed
                 | TestError ExitCode
-                | TestFailed String FilePath [Diff String]
+                | TestFailed String FilePath [Diff Text]
      deriving (Eq)
 
 instance Show TestResult where
   show TestPassed     = "PASSED"
-  show (TestError ec) = "ERROR " ++ show ec
-  show (TestFailed cmd file d) = '\n' : dash ++
-                                 "\n--- " ++ file ++
-                                 "\n+++ " ++ cmd ++ "\n" ++ showDiff (1,1) d ++
-                                 dash
+  show (TestError ec) = "ERROR " <> show ec
+  show (TestFailed cmd file d) = "\n" <> dash <>
+                                 "\n--- " <> file <>
+                                 "\n+++ " <> cmd <> "\n" <>
+                                 showDiff (1,1) d <> dash
     where dash = replicate 72 '-'
 
-showDiff :: (Int,Int) -> [Diff String] -> String
+showDiff :: ToString a => (Int,Int) -> [Diff a] -> String
 showDiff _ []             = ""
 showDiff (l,r) (First ln : ds) =
-  printf "+%4d " l ++ ln ++ "\n" ++ showDiff (l+1,r) ds
+  printf "+%4d " l <> toString ln <> "\n" <> showDiff (l+1,r) ds
 showDiff (l,r) (Second ln : ds) =
-  printf "-%4d " r ++ ln ++ "\n" ++ showDiff (l,r+1) ds
+  printf "-%4d " r <> toString ln <> "\n" <> showDiff (l,r+1) ds
 showDiff (l,r) (Both _ _ : ds) =
   showDiff (l+1,r+1) ds
 
-vividize :: Diff String -> String
-vividize (Both s _) = "  " ++ s
-vividize (First s)  = "- " ++ s
-vividize (Second s) = "+ " ++ s
+vividize :: Diff Text -> Text
+vividize (Both s _) = "  " <> s
+vividize (First s)  = "- " <> s
+vividize (Second s) = "+ " <> s
 
 purely :: (b -> PandocPure a) -> b -> a
 purely f = either (error . show) id . runPure . f
@@ -92,28 +97,28 @@ infix 5 =?>
 (=?>) :: a -> b -> (a,b)
 x =?> y = (x, y)
 
-class ToString a where
-  toString :: a -> String
-
 instance ToString Pandoc where
-  toString d = unpack $
-     purely (writeNative def{ writerTemplate = s }) $ toPandoc d
-   where s = case d of
-                  (Pandoc (Meta m) _)
-                    | M.null m  -> Nothing
-                    | otherwise -> Just mempty -- need this to get meta output
+  toString = T.unpack . toText
 
 instance ToString Blocks where
-  toString = unpack . purely (writeNative def) . toPandoc
+  toString = T.unpack . toText
 
 instance ToString Inlines where
-  toString = unpack . trimr . purely (writeNative def) . toPandoc
+  toString = T.unpack . toText
+
+instance ToText Pandoc where
+  toText d@(Pandoc (Meta m) _)
+    | M.null m
+    = purely (writeNative def) $ toPandoc d
+  toText d@(Pandoc m _)
+   = purely (writeNative def{ writerTemplate = Just mempty }) $ toPandoc d
+                              -- need this to get meta output
 
-instance ToString String where
-  toString = id
+instance ToText Blocks where
+  toText = purely (writeNative def) . toPandoc
 
-instance ToString Text where
-  toString = unpack
+instance ToText Inlines where
+  toText = T.stripEnd . purely (writeNative def) . toPandoc
 
 class ToPandoc a where
   toPandoc :: a -> Pandoc
diff --git a/test/Tests/Lua.hs b/test/Tests/Lua.hs
index 31c011900..35be57da7 100644
--- a/test/Tests/Lua.hs
+++ b/test/Tests/Lua.hs
@@ -230,7 +230,7 @@ roundtripEqual x = (x ==) <$> roundtripped
     Lua.push x
     size <- Lua.gettop
     when (size - oldSize /= 1) $
-      error ("not exactly one additional element on the stack: " ++ show size)
+      error ("not exactly one additional element on the stack: " <> show size)
     Lua.peek (-1)
 
 runLuaTest :: Lua.Lua a -> IO a
diff --git a/test/Tests/Old.hs b/test/Tests/Old.hs
index 160086be2..fefe36795 100644
--- a/test/Tests/Old.hs
+++ b/test/Tests/Old.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE TupleSections #-}
+{-# LANGUAGE OverloadedStrings #-}
 {- |
    Module      : Tests.Old
    Copyright   : © 2006-2021 John MacFarlane
@@ -229,10 +230,6 @@ tests pandocPath =
     lhsReaderTest'  = lhsReaderTest pandocPath
     extWriterTests' = extendedWriterTests pandocPath
 
--- makes sure file is fully closed after reading
-readFile' :: FilePath -> IO String
-readFile' f = do s <- UTF8.readFile f
-                 return $! (T.length s `seq` T.unpack s)
 
 lhsWriterTests :: FilePath -> String -> [TestTree]
 lhsWriterTests pandocPath format
@@ -289,13 +286,9 @@ fb2WriterTest pandocPath title opts inputfile normfile =
   testWithNormalize (ignoreBinary . formatXML) pandocPath
                     title (["-t", "fb2"]++opts) inputfile normfile
   where
-    formatXML xml = splitTags $ zip xml (drop 1 xml)
-    splitTags []               = []
-    splitTags [end]            = [fst end, snd end]
-    splitTags (('>','<'):rest) = ">\n" ++ splitTags rest
-    splitTags ((c,_):rest)     = c : splitTags rest
+    formatXML = T.replace "><" ">\n<"
     ignoreBinary = unlines . filter (not . startsWith "<binary ") . lines
-    startsWith tag str = all (uncurry (==)) $ zip tag str
+    startsWith tag str = tag `T.isPrefixOf` str
 
 -- | Run a test without normalize function, return True if test passed.
 test :: FilePath  -- ^ Path of pandoc executable
@@ -307,7 +300,7 @@ test :: FilePath  -- ^ Path of pandoc executable
 test = testWithNormalize id
 
 -- | Run a test with normalize function, return True if test passed.
-testWithNormalize  :: (String -> String) -- ^ Normalize function for output
+testWithNormalize  :: (Text -> Text) -- ^ Normalize function for output
                    -> FilePath  -- ^ Path to pandoc executable
                    -> String    -- ^ Title of test
                    -> [String]  -- ^ Options to pass to pandoc
@@ -317,7 +310,7 @@ testWithNormalize  :: (String -> String) -- ^ Normalize function for output
 testWithNormalize normalizer pandocPath testname opts inp norm =
   goldenTest testname getExpected getActual
     (compareValues norm options) updateGolden
-  where getExpected = normalizer <$> readFile' norm
+  where getExpected = normalizer <$> UTF8.readFile norm
         getActual   = do
               mldpath   <- Env.lookupEnv "LD_LIBRARY_PATH"
               mdyldpath <- Env.lookupEnv "DYLD_LIBRARY_PATH"
@@ -330,23 +323,23 @@ testWithNormalize normalizer pandocPath testname opts inp norm =
               (ec, out) <- pipeProcess (Just env) pandocPath
                              ("--emulate":options) mempty
               if ec == ExitSuccess
-                 then return $ filter (/='\r') . normalizer
+                 then return $ normalizer $ T.pack $ filter (/='\r')
                              $ UTF8.toStringLazy out
                    -- filter \r so the tests will work on Windows machines
                  else fail $ "Pandoc failed with error code " ++ show ec
-        updateGolden = UTF8.writeFile norm . T.pack
+        updateGolden = UTF8.writeFile norm
         options = ["--data-dir=../data","--quiet"] ++ [inp] ++ opts
 
-compareValues :: FilePath -> [String] -> String -> String -> IO (Maybe String)
+compareValues :: FilePath -> [String] -> Text -> Text -> IO (Maybe String)
 compareValues norm options expected actual = do
   testExePath <- getExecutablePath
-  let cmd  = testExePath ++ " --emulate " ++ unwords options
+  let cmd  = testExePath ++ " --emulate " ++ intercalate " " options
   let dash = replicate 72 '-'
   let diff = getDiff (lines actual) (lines expected)
   if expected == actual
      then return Nothing
      else return $ Just $
-        '\n' : dash ++
-        "\n--- " ++ norm ++
-        "\n+++ " ++ cmd ++ "\n" ++
-        showDiff (1,1) diff ++ dash
+        "\n" <> dash <>
+        "\n--- " <> norm <>
+        "\n<>+ " <> cmd <> "\n" <>
+        showDiff (1,1) diff <> dash
diff --git a/test/Tests/Readers/Creole.hs b/test/Tests/Readers/Creole.hs
index 3320b78e8..582df693b 100644
--- a/test/Tests/Readers/Creole.hs
+++ b/test/Tests/Readers/Creole.hs
@@ -25,7 +25,7 @@ creole :: Text -> Pandoc
 creole = purely $ readCreole def{ readerStandalone = True }
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test creole
 
diff --git a/test/Tests/Readers/Docx.hs b/test/Tests/Readers/Docx.hs
index 263e04173..59bac0213 100644
--- a/test/Tests/Readers/Docx.hs
+++ b/test/Tests/Readers/Docx.hs
@@ -40,8 +40,8 @@ noNorm = NoNormPandoc
 defopts :: ReaderOptions
 defopts = def{ readerExtensions = getDefaultExtensions "docx" }
 
-instance ToString NoNormPandoc where
-  toString d = T.unpack $ purely (writeNative def{ writerTemplate = s }) $ toPandoc d
+instance ToText NoNormPandoc where
+  toText d = purely (writeNative def{ writerTemplate = s }) $ toPandoc d
    where s = case d of
                   NoNormPandoc (Pandoc (Meta m) _)
                     | M.null m  -> Nothing
@@ -73,14 +73,14 @@ testCompareWithOpts opts name docxFile nativeFile =
 testCompare :: String -> FilePath -> FilePath -> TestTree
 testCompare = testCompareWithOpts defopts
 
-testForWarningsWithOptsIO :: ReaderOptions -> String -> FilePath -> [String] -> IO TestTree
+testForWarningsWithOptsIO :: ReaderOptions -> String -> FilePath -> [Text] -> IO TestTree
 testForWarningsWithOptsIO opts name docxFile expected = do
   df <- B.readFile docxFile
   logs <-  runIOorExplode $ setVerbosity ERROR >> readDocx opts df >> P.getLog
   let warns = [m | DocxParserWarning m <- logs]
-  return $ test id name (T.unlines warns, unlines expected)
+  return $ test id name (T.unlines warns, T.unlines expected)
 
-testForWarningsWithOpts :: ReaderOptions -> String -> FilePath -> [String] -> TestTree
+testForWarningsWithOpts :: ReaderOptions -> String -> FilePath -> [Text] -> TestTree
 testForWarningsWithOpts opts name docxFile expected =
   unsafePerformIO $ testForWarningsWithOptsIO opts name docxFile expected
 
@@ -96,10 +96,10 @@ compareMediaPathIO mediaPath mediaBag docxPath = do
   docxMedia <- getMedia docxPath mediaPath
   let mbBS   = case lookupMedia mediaPath mediaBag of
                  Just (_, bs) -> bs
-                 Nothing      -> error ("couldn't find " ++
+                 Nothing      -> error $ T.pack ("couldn't find " ++
                                         mediaPath ++
                                         " in media bag")
-      docxBS = fromMaybe (error ("couldn't find " ++
+      docxBS = fromMaybe (error $ T.pack ("couldn't find " ++
                         mediaPath ++
                         " in media bag")) docxMedia
   return $ mbBS == docxBS
diff --git a/test/Tests/Readers/DokuWiki.hs b/test/Tests/Readers/DokuWiki.hs
index 84ba86d46..fa344b910 100644
--- a/test/Tests/Readers/DokuWiki.hs
+++ b/test/Tests/Readers/DokuWiki.hs
@@ -19,13 +19,13 @@ import Test.Tasty
 import Tests.Helpers
 import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 
 dokuwiki :: Text -> Pandoc
 dokuwiki = purely $ readDokuWiki def{ readerStandalone = True }
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test dokuwiki
 
diff --git a/test/Tests/Readers/FB2.hs b/test/Tests/Readers/FB2.hs
index 42054a235..ac7db9be1 100644
--- a/test/Tests/Readers/FB2.hs
+++ b/test/Tests/Readers/FB2.hs
@@ -16,7 +16,7 @@ import Tests.Helpers
 import Test.Tasty.Golden (goldenVsString)
 import qualified Data.ByteString as BS
 import Text.Pandoc
-import Text.Pandoc.UTF8 (toText, fromStringLazy)
+import Text.Pandoc.UTF8 as UTF8
 import Data.Text (Text, unpack)
 import System.FilePath (replaceExtension)
 
@@ -25,7 +25,7 @@ fb2ToNative = purely (writeNative def{ writerTemplate = Just mempty }) . purely
 
 fb2Test :: TestName -> FilePath -> TestTree
 fb2Test name path = goldenVsString name native
-  (fromStringLazy . filter (/='\r') . unpack . fb2ToNative . toText
+  (UTF8.fromStringLazy . filter (/='\r') . unpack . fb2ToNative . UTF8.toText
     <$> BS.readFile path)
   where native = replaceExtension path ".native"
 
diff --git a/test/Tests/Readers/HTML.hs b/test/Tests/Readers/HTML.hs
index f23af2cb1..6a8a10cef 100644
--- a/test/Tests/Readers/HTML.hs
+++ b/test/Tests/Readers/HTML.hs
@@ -21,7 +21,7 @@ import Tests.Helpers
 import Text.Pandoc
 import Text.Pandoc.Shared (isHeaderBlock)
 import Text.Pandoc.Arbitrary ()
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 import Text.Pandoc.Walk (walk)
 
 html :: Text -> Pandoc
@@ -47,7 +47,7 @@ removeRawInlines x           = x
 roundTrip :: Blocks -> Bool
 roundTrip b = d'' == d'''
   where d = walk removeRawInlines $
-            walk makeRoundTrip $ Pandoc nullMeta $ toList b
+            walk makeRoundTrip $ Pandoc nullMeta $ B.toList b
         d' = rewrite d
         d'' = rewrite d'
         d''' = rewrite d''
diff --git a/test/Tests/Readers/Jira.hs b/test/Tests/Readers/Jira.hs
index cb7dde4ea..2881a83e5 100644
--- a/test/Tests/Readers/Jira.hs
+++ b/test/Tests/Readers/Jira.hs
@@ -25,7 +25,7 @@ jira :: Text -> Pandoc
 jira = purely $ readJira def
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test jira
 
diff --git a/test/Tests/Readers/LaTeX.hs b/test/Tests/Readers/LaTeX.hs
index 4bda15140..a631e55af 100644
--- a/test/Tests/Readers/LaTeX.hs
+++ b/test/Tests/Readers/LaTeX.hs
@@ -18,14 +18,14 @@ import Test.Tasty
 import Tests.Helpers
 import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 
 latex :: Text -> Pandoc
 latex = purely $ readLaTeX def{
                    readerExtensions = getDefaultExtensions "latex" }
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test latex
 
@@ -338,10 +338,10 @@ natbibCitations = testGroup "natbib"
     =?> para (cite [baseCitation] (rt "\\citet{item1}"))
   , "suffix" =: "\\citet[p.~30]{item1}"
     =?> para
-        (cite [baseCitation{ citationSuffix = toList $ text "p.\160\&30" }] (rt "\\citet[p.~30]{item1}"))
+        (cite [baseCitation{ citationSuffix = B.toList $ text "p.\160\&30" }] (rt "\\citet[p.~30]{item1}"))
   , "suffix long" =: "\\citet[p.~30, with suffix]{item1}"
     =?> para (cite [baseCitation{ citationSuffix =
-                       toList $ text "p.\160\&30, with suffix" }] (rt "\\citet[p.~30, with suffix]{item1}"))
+                       B.toList $ text "p.\160\&30, with suffix" }] (rt "\\citet[p.~30, with suffix]{item1}"))
   , "multiple" =: "\\citeauthor{item1} \\citetext{\\citeyear{item1}; \\citeyear[p.~30]{item2}; \\citealp[see also][]{item3}}"
     =?> para (cite [baseCitation{ citationMode = AuthorInText }
                    ,baseCitation{ citationMode = SuppressAuthor
@@ -365,7 +365,7 @@ natbibCitations = testGroup "natbib"
                                 , citationSuffix = [Str "pp.\160\&33,",Space,Str "35\8211\&37,",Space,Str "and",Space,Str "nowhere",Space, Str "else"] }] (rt "\\citep[pp.~33, 35--37, and nowhere else]{item1}"))
   , "suffix only" =: "\\citep[and nowhere else]{item1}"
     =?> para (cite [baseCitation{ citationMode = NormalCitation
-                                , citationSuffix = toList $ text "and nowhere else" }] (rt "\\citep[and nowhere else]{item1}"))
+                                , citationSuffix = B.toList $ text "and nowhere else" }] (rt "\\citep[and nowhere else]{item1}"))
   , "no author" =: "\\citeyearpar{item1}, and now Doe with a locator \\citeyearpar[p.~44]{item2}"
     =?> para (cite [baseCitation{ citationMode = SuppressAuthor }] (rt "\\citeyearpar{item1}") <>
               text ", and now Doe with a locator " <>
@@ -385,10 +385,10 @@ biblatexCitations = testGroup "biblatex"
     =?> para (cite [baseCitation] (rt "\\textcite{item1}"))
   , "suffix" =: "\\textcite[p.~30]{item1}"
     =?> para
-        (cite [baseCitation{ citationSuffix = toList $ text "p.\160\&30" }] (rt "\\textcite[p.~30]{item1}"))
+        (cite [baseCitation{ citationSuffix = B.toList $ text "p.\160\&30" }] (rt "\\textcite[p.~30]{item1}"))
   , "suffix long" =: "\\textcite[p.~30, with suffix]{item1}"
     =?> para (cite [baseCitation{ citationSuffix =
-                       toList $ text "p.\160\&30, with suffix" }] (rt "\\textcite[p.~30, with suffix]{item1}"))
+                       B.toList $ text "p.\160\&30, with suffix" }] (rt "\\textcite[p.~30, with suffix]{item1}"))
   , "multiple" =: "\\textcites{item1}[p.~30]{item2}[see also][]{item3}"
     =?> para (cite [baseCitation{ citationMode = AuthorInText }
                    ,baseCitation{ citationMode = NormalCitation
@@ -412,7 +412,7 @@ biblatexCitations = testGroup "biblatex"
                                 , citationSuffix = [Str "pp.\160\&33,",Space,Str "35\8211\&37,",Space,Str "and",Space,Str "nowhere",Space, Str "else"] }] (rt "\\autocite[pp.~33, 35--37, and nowhere else]{item1}"))
   , "suffix only" =: "\\autocite[and nowhere else]{item1}"
     =?> para (cite [baseCitation{ citationMode = NormalCitation
-                                , citationSuffix = toList $ text "and nowhere else" }] (rt "\\autocite[and nowhere else]{item1}"))
+                                , citationSuffix = B.toList $ text "and nowhere else" }] (rt "\\autocite[and nowhere else]{item1}"))
   , "no author" =: "\\autocite*{item1}, and now Doe with a locator \\autocite*[p.~44]{item2}"
     =?> para (cite [baseCitation{ citationMode = SuppressAuthor }] (rt "\\autocite*{item1}") <>
               text ", and now Doe with a locator " <>
diff --git a/test/Tests/Readers/Man.hs b/test/Tests/Readers/Man.hs
index d36151d58..ff1f14a29 100644
--- a/test/Tests/Readers/Man.hs
+++ b/test/Tests/Readers/Man.hs
@@ -18,14 +18,14 @@ import Test.Tasty
 import Tests.Helpers
 import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 import Text.Pandoc.Readers.Man
 
 man :: Text -> Pandoc
 man = purely $ readMan def
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test man
 
diff --git a/test/Tests/Readers/Markdown.hs b/test/Tests/Readers/Markdown.hs
index 0930deae6..8e6700639 100644
--- a/test/Tests/Readers/Markdown.hs
+++ b/test/Tests/Readers/Markdown.hs
@@ -19,6 +19,7 @@ import Tests.Helpers
 import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
 import Text.Pandoc.Builder
+import qualified Relude.Unsafe as Unsafe
 
 markdown :: Text -> Pandoc
 markdown = purely $ readMarkdown def { readerExtensions =
@@ -37,7 +38,7 @@ markdownGH = purely $ readMarkdown def {
                 readerExtensions = githubMarkdownExtensions }
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test markdown
 
@@ -205,15 +206,15 @@ tests = [ testGroup "inline code"
              ]
           <> [ "lists with newlines and indent in backticks" =:
                T.intercalate ("\n" <> T.replicate 4 " ") (zipWith (\i (_, lt, _) -> lt <> i) lis lsts)
-               =?> let (_, _, f) = head lsts
-                   in f [plain $ code $ T.intercalate (T.replicate 5 " ") $ head lis' : zipWith (\i (_, lt, _) -> lt <> i) (tail lis') (tail lsts)]
+               =?> let (_, _, f) = Unsafe.head lsts
+                   in f [plain $ code $ T.intercalate (T.replicate 5 " ") $ Unsafe.head lis' : zipWith (\i (_, lt, _) -> lt <> i) (Unsafe.tail lis') (Unsafe.tail lsts)]
              | lsts <- [ [i, j, k] | i <- lists, j <- lists, k <- lists]
              ]
           <> [ "lists with blank lines and indent in backticks" =:
                T.intercalate ("\n\n" <> T.replicate 4 " ") (zipWith (\i (_, lt, _) -> lt <> i) lis lsts)
                <> "\n"
-               =?> let (_, _, f) = head lsts
-                   in f . pure $ (para . text $ head lis) <> bldLsts para (tail lsts) (tail lis)
+               =?> let (_, _, f) = Unsafe.head lsts
+                   in f . pure $ (para . text $ Unsafe.head lis) <> bldLsts para (Unsafe.tail lsts) (Unsafe.tail lis)
              | lsts <- [ [i, j, k] | i <- lists, j <- lists, k <- lists]
              ]
         , testGroup "emph and strong"
diff --git a/test/Tests/Readers/Muse.hs b/test/Tests/Readers/Muse.hs
index 68bdc87b4..6304a0dd8 100644
--- a/test/Tests/Readers/Muse.hs
+++ b/test/Tests/Readers/Muse.hs
@@ -22,7 +22,7 @@ import Test.Tasty.Options (IsOption(defaultValue))
 import Tests.Helpers
 import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 import Text.Pandoc.Writers.Shared (toLegacyTable)
 import Text.Pandoc.Walk
 
@@ -33,7 +33,7 @@ emacsMuse :: Text -> Pandoc
 emacsMuse = purely $ readMuse def { readerExtensions = emptyExtensions }
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test amuse
 
@@ -59,7 +59,8 @@ makeRoundTrip t@(Table tattr blkCapt specs thead tbody tfoot) =
     then t
     else Para [Str "table was here"]
   where (_, aligns, widths, headers, rows) = toLegacyTable blkCapt specs thead tbody tfoot
-        numcols = maximum (length aligns : length widths : map length (headers:rows))
+        numcols = maximum1
+                  (length aligns :| length widths : map length (headers:rows))
         isLineBreak LineBreak = Any True
         isLineBreak _         = Any False
         hasLineBreak = getAny . query isLineBreak
@@ -107,7 +108,7 @@ makeRoundTrip x = x
 -- Currently we remove tables and compare first rewrite to the second.
 roundTrip :: Blocks -> Bool
 roundTrip b = d' == d''
-  where d = walk makeRoundTrip $ Pandoc nullMeta $ toList b
+  where d = walk makeRoundTrip $ Pandoc nullMeta $ B.toList b
         d' = rewrite d
         d'' = rewrite d'
         rewrite = amuse . T.pack . (++ "\n") . T.unpack .
@@ -801,7 +802,7 @@ tests =
       , testGroup "Directives"
         [ "Title" =:
           "#title Document title" =?>
-          let titleInline = toList "Document title"
+          let titleInline = B.toList "Document title"
               meta = setMeta "title" (MetaInlines titleInline) nullMeta
           in Pandoc meta mempty
         -- Emacs Muse documentation says that "You can use any combination
@@ -809,25 +810,25 @@ tests =
         -- but also allows '-', which is not documented, but used for disable-tables.
         , test emacsMuse "Disable tables"
           ("#disable-tables t" =?>
-          Pandoc (setMeta "disable-tables" (MetaInlines $ toList "t") nullMeta) mempty)
+          Pandoc (setMeta "disable-tables" (MetaInlines $ B.toList "t") nullMeta) mempty)
         , "Multiple directives" =:
           T.unlines [ "#title Document title"
                     , "#subtitle Document subtitle"
                     ] =?>
-          Pandoc (setMeta "title" (MetaInlines $ toList "Document title") $
-                  setMeta "subtitle" (MetaInlines $ toList "Document subtitle") nullMeta) mempty
+          Pandoc (setMeta "title" (MetaInlines $ B.toList "Document title") $
+                  setMeta "subtitle" (MetaInlines $ B.toList "Document subtitle") nullMeta) mempty
         , "Multiline directive" =:
           T.unlines [ "#title Document title"
                     , "#notes First line"
                     , "and second line"
                     , "#author Name"
                     ] =?>
-          Pandoc (setMeta "title" (MetaInlines $ toList "Document title") $
-                  setMeta "notes" (MetaInlines $ toList "First line\nand second line") $
-                  setMeta "author" (MetaInlines $ toList "Name") nullMeta) mempty
+          Pandoc (setMeta "title" (MetaInlines $ B.toList "Document title") $
+                  setMeta "notes" (MetaInlines $ B.toList "First line\nand second line") $
+                  setMeta "author" (MetaInlines $ B.toList "Name") nullMeta) mempty
         , "Amusewiki's #cover is translated to pandoc's #cover-image" =:
           "#cover cover.png" =?>
-          let titleInline = toList "cover.png"
+          let titleInline = B.toList "cover.png"
               meta = setMeta "cover-image" (MetaInlines titleInline) nullMeta
           in Pandoc meta mempty
         ]
diff --git a/test/Tests/Readers/Odt.hs b/test/Tests/Readers/Odt.hs
index 9b5ec6b9e..f1155d23e 100644
--- a/test/Tests/Readers/Odt.hs
+++ b/test/Tests/Readers/Odt.hs
@@ -17,7 +17,7 @@ import Control.Monad (liftM)
 import qualified Data.ByteString as BS
 import qualified Data.ByteString.Lazy as B
 import qualified Data.Map as M
-import Data.Text (unpack)
+import qualified Data.Text as T
 import System.IO.Unsafe (unsafePerformIO)
 import Test.Tasty
 import Tests.Helpers
@@ -54,9 +54,8 @@ testsComparingToNative      = map nameToTest namesOfTestsComparingToNative
 newtype NoNormPandoc = NoNormPandoc {unNoNorm :: Pandoc}
   deriving ( Show )
 
-instance ToString NoNormPandoc where
-  toString d = unpack $
-               purely (writeNative def{ writerTemplate = s }) $ toPandoc d
+instance ToText NoNormPandoc where
+  toText d = purely (writeNative def{ writerTemplate = s }) $ toPandoc d
    where s = case d of
                   NoNormPandoc (Pandoc (Meta m) _)
                     | M.null m  -> Nothing
@@ -66,7 +65,8 @@ instance ToPandoc NoNormPandoc where
   toPandoc = unNoNorm
 
 getNoNormVia :: (a -> Pandoc) -> String -> Either PandocError a -> NoNormPandoc
-getNoNormVia _ readerName (Left  _) = error (readerName ++ " reader failed")
+getNoNormVia _ readerName (Left  _) =
+  error $ T.pack (readerName ++ " reader failed")
 getNoNormVia f _          (Right a) = NoNormPandoc (f a)
 
 type TestCreator =  ReaderOptions
diff --git a/test/Tests/Readers/Org/Directive.hs b/test/Tests/Readers/Org/Directive.hs
index 85d1bc088..c2409ce80 100644
--- a/test/Tests/Readers/Org/Directive.hs
+++ b/test/Tests/Readers/Org/Directive.hs
@@ -15,14 +15,14 @@ module Tests.Readers.Org.Directive (tests) where
 import Data.Time (UTCTime (UTCTime), secondsToDiffTime)
 import Data.Time.Calendar (Day (ModifiedJulianDay))
 import Test.Tasty (TestTree, testGroup)
-import Tests.Helpers ((=?>), ToString, purely, test)
+import Tests.Helpers ((=?>), ToString, ToText, purely, test)
 import Tests.Readers.Org.Shared ((=:), tagSpan)
 import Text.Pandoc
 import Text.Pandoc.Builder
 import qualified Data.ByteString as BS
 import qualified Data.Text as T
 
-testWithFiles :: (ToString c)
+testWithFiles :: (ToText c)
               => [(FilePath, BS.ByteString)]
               -> String         -- ^ name of test case
               -> (T.Text, c)    -- ^ (input, expected value)
diff --git a/test/Tests/Readers/Org/Inline/Citation.hs b/test/Tests/Readers/Org/Inline/Citation.hs
index a11804983..fa1560772 100644
--- a/test/Tests/Readers/Org/Inline/Citation.hs
+++ b/test/Tests/Readers/Org/Inline/Citation.hs
@@ -15,7 +15,7 @@ module Tests.Readers.Org.Inline.Citation (tests) where
 import Test.Tasty (TestTree, testGroup)
 import Tests.Helpers ((=?>))
 import Tests.Readers.Org.Shared ((=:))
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 
 tests :: [TestTree]
 tests =
@@ -160,8 +160,8 @@ tests =
       "[[citep:Dominik201408][See page 20::, for example]]" =?>
       let citation = Citation
                      { citationId = "Dominik201408"
-                     , citationPrefix = toList "See page 20"
-                     , citationSuffix = toList ", for example"
+                     , citationPrefix = B.toList "See page 20"
+                     , citationSuffix = B.toList ", for example"
                      , citationMode = NormalCitation
                      , citationNoteNum = 0
                      , citationHash = 0
@@ -198,17 +198,17 @@ tests =
       , "Berkeley-style parenthetical citation list" =:
         "[(cite): see; @Dominik201408;also @Pandoc; and others]" =?>
         let pandocCite'  = pandocCite {
-                             citationPrefix = toList "also"
-                           , citationSuffix = toList "and others"
+                             citationPrefix = B.toList "also"
+                           , citationSuffix = B.toList "and others"
                            }
             dominikCite' = dominikCite {
-                             citationPrefix = toList "see"
+                             citationPrefix = B.toList "see"
                            }
         in (para $ cite [dominikCite', pandocCite'] "")
 
       , "Berkeley-style plain citation list" =:
         "[cite: See; @Dominik201408; and @Pandoc; and others]" =?>
-        let pandocCite' = pandocInText { citationPrefix = toList "and" }
+        let pandocCite' = pandocInText { citationPrefix = B.toList "and" }
         in (para $ "See "
              <> cite [dominikInText] ""
              <> "," <> space
diff --git a/test/Tests/Readers/Org/Meta.hs b/test/Tests/Readers/Org/Meta.hs
index 6363d84b0..f38ee7194 100644
--- a/test/Tests/Readers/Org/Meta.hs
+++ b/test/Tests/Readers/Org/Meta.hs
@@ -16,7 +16,7 @@ import Test.Tasty (TestTree, testGroup)
 import Tests.Helpers ((=?>))
 import Tests.Readers.Org.Shared ((=:), spcSep)
 import Text.Pandoc
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 import qualified Data.Text as T
 
 tests :: [TestTree]
@@ -43,14 +43,14 @@ tests =
   , testGroup "Export settings"
     [ "Title" =:
       "#+title: Hello, World" =?>
-      let titleInline = toList $ "Hello," <> space <> "World"
+      let titleInline = B.toList $ "Hello," <> space <> "World"
           meta = setMeta "title" (MetaInlines titleInline) nullMeta
       in Pandoc meta mempty
 
     , testGroup "Author"
       [ "sets 'author' field" =:
         "#+author: John /Emacs-Fanboy/ Doe" =?>
-        let author = toList . spcSep $ [ "John", emph "Emacs-Fanboy", "Doe" ]
+        let author = B.toList . spcSep $ [ "John", emph "Emacs-Fanboy", "Doe" ]
             meta = setMeta "author" (MetaInlines author) nullMeta
         in Pandoc meta mempty
 
@@ -58,8 +58,8 @@ tests =
         T.unlines [ "#+author: James Dewey Watson,"
                   , "#+author: Francis Harry Compton Crick"
                   ] =?>
-        let watson = toList "James Dewey Watson,"
-            crick = toList "Francis Harry Compton Crick"
+        let watson = B.toList "James Dewey Watson,"
+            crick = B.toList "Francis Harry Compton Crick"
             meta = setMeta "author"
                            (MetaInlines (watson ++ SoftBreak : crick))
                            nullMeta
@@ -68,7 +68,7 @@ tests =
 
     , "Date" =:
       "#+date: Feb. *28*, 2014" =?>
-      let date = toList . spcSep $ [ "Feb.", strong "28" <> ",", "2014" ]
+      let date = B.toList . spcSep $ [ "Feb.", strong "28" <> ",", "2014" ]
           meta = setMeta "date" (MetaInlines date) nullMeta
       in Pandoc meta mempty
 
@@ -102,7 +102,7 @@ tests =
       T.unlines [ "#+keywords: pandoc, testing,"
                 , "#+keywords: Org"
                 ] =?>
-      let keywords = toList $ "pandoc, testing," <> softbreak <> "Org"
+      let keywords = B.toList $ "pandoc, testing," <> softbreak <> "Org"
           meta = setMeta "keywords" (MetaInlines keywords) nullMeta
       in Pandoc meta mempty
 
@@ -128,7 +128,7 @@ tests =
       [ "LATEX_HEADER" =:
         "#+latex_header: \\usepackage{tikz}" =?>
         let latexInlines = rawInline "latex" "\\usepackage{tikz}"
-            inclList = MetaList [MetaInlines (toList latexInlines)]
+            inclList = MetaList [MetaInlines (B.toList latexInlines)]
             meta = setMeta "header-includes" inclList nullMeta
         in Pandoc meta mempty
 
@@ -162,7 +162,7 @@ tests =
       [ "HTML_HEAD values are added to header-includes" =:
         "#+html_head: <meta/>" =?>
         let html = rawInline "html" "<meta/>"
-            inclList = MetaList [MetaInlines (toList html)]
+            inclList = MetaList [MetaInlines (B.toList html)]
             meta = setMeta "header-includes" inclList nullMeta
         in Pandoc meta mempty
 
diff --git a/test/Tests/Readers/Org/Shared.hs b/test/Tests/Readers/Org/Shared.hs
index c584eff19..a1baaf75e 100644
--- a/test/Tests/Readers/Org/Shared.hs
+++ b/test/Tests/Readers/Org/Shared.hs
@@ -29,7 +29,7 @@ org :: Text -> Pandoc
 org = purely $ readOrg def{ readerExtensions = getDefaultExtensions "org" }
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test org
 
diff --git a/test/Tests/Readers/RST.hs b/test/Tests/Readers/RST.hs
index a12b59fc2..95e64c489 100644
--- a/test/Tests/Readers/RST.hs
+++ b/test/Tests/Readers/RST.hs
@@ -25,7 +25,7 @@ rst :: Text -> Pandoc
 rst = purely $ readRST def{ readerStandalone = True }
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test rst
 
diff --git a/test/Tests/Readers/Txt2Tags.hs b/test/Tests/Readers/Txt2Tags.hs
index 013f29d68..eb96b20ee 100644
--- a/test/Tests/Readers/Txt2Tags.hs
+++ b/test/Tests/Readers/Txt2Tags.hs
@@ -30,7 +30,7 @@ t2t = purely $ \s -> do
   readTxt2Tags def s
 
 infix 4 =:
-(=:) :: ToString c
+(=:) :: ToText c
      => String -> (Text, c) -> TestTree
 (=:) = test t2t
 
diff --git a/test/Tests/Shared.hs b/test/Tests/Shared.hs
index e415ea153..287c3a61b 100644
--- a/test/Tests/Shared.hs
+++ b/test/Tests/Shared.hs
@@ -16,7 +16,7 @@ import System.FilePath.Posix (joinPath)
 import Test.Tasty
 import Test.Tasty.HUnit (assertBool, testCase, (@?=))
 import Text.Pandoc.Arbitrary ()
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 import Text.Pandoc.Shared
 import Text.Pandoc.Writers.Shared (toLegacyTable)
 
@@ -58,7 +58,7 @@ testLegacyTable =
   , testCase "decomposes a table without head" $ gen2 @?= expect2
   ]
   where
-    pln = toList . plain . str
+    pln = B.toList . plain . str
     cl a h w = Cell ("", [], []) AlignDefault h w $ pln a
     rws = map $ Row nullAttr
     th = TableHead nullAttr . rws
diff --git a/test/Tests/Writers/AnnotatedTable.hs b/test/Tests/Writers/AnnotatedTable.hs
index 53cca80a6..8e8ce9d3e 100644
--- a/test/Tests/Writers/AnnotatedTable.hs
+++ b/test/Tests/Writers/AnnotatedTable.hs
@@ -35,7 +35,7 @@ import           Test.Tasty.QuickCheck          ( QuickCheckTests(..)
                                                 , elements
                                                 )
 import           Text.Pandoc.Arbitrary          ( )
-import           Text.Pandoc.Builder
+import           Text.Pandoc.Builder           as B
 import qualified Text.Pandoc.Writers.AnnotatedTable
                                                as Ann
 
@@ -150,7 +150,7 @@ propBuilderAnnTable th tbs tf = withColSpec $ \cs ->
   convertTable (table emptyCaption cs th tbs tf)
     === convertAnnTable (Ann.toTable nullAttr emptyCaption cs th tbs tf)
  where
-  convertTable blks = case toList blks of
+  convertTable blks = case B.toList blks of
     [Table _ _ colspec a b c] -> Right (colspec, a, b, c)
     x                         -> Left x
   convertAnnTable x = case Ann.fromTable x of
diff --git a/test/Tests/Writers/AsciiDoc.hs b/test/Tests/Writers/AsciiDoc.hs
index 04655635f..6ab2bdb0d 100644
--- a/test/Tests/Writers/AsciiDoc.hs
+++ b/test/Tests/Writers/AsciiDoc.hs
@@ -11,9 +11,9 @@ import Text.Pandoc.Builder
 asciidoc :: (ToPandoc a) => a -> String
 asciidoc = unpack . purely (writeAsciiDoc def{ writerWrapText = WrapNone }) . toPandoc
 
-testAsciidoc :: (ToString a, ToPandoc a)
+testAsciidoc :: (ToText a, ToPandoc a)
              => String
-             -> (a, String)
+             -> (a, Text)
              -> TestTree
 testAsciidoc = test asciidoc
 
diff --git a/test/Tests/Writers/ConTeXt.hs b/test/Tests/Writers/ConTeXt.hs
index 5c1c98d4e..6aea41c85 100644
--- a/test/Tests/Writers/ConTeXt.hs
+++ b/test/Tests/Writers/ConTeXt.hs
@@ -34,8 +34,8 @@ which is in turn shorthand for
 -}
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test context
 
 tests :: [TestTree]
diff --git a/test/Tests/Writers/Docbook.hs b/test/Tests/Writers/Docbook.hs
index 842aed7ae..657461366 100644
--- a/test/Tests/Writers/Docbook.hs
+++ b/test/Tests/Writers/Docbook.hs
@@ -8,11 +8,11 @@ import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
 import Text.Pandoc.Builder
 
-docbook :: (ToPandoc a) => a -> String
+docbook :: (ToPandoc a) => a -> Text
 docbook = docbookWithOpts def{ writerWrapText = WrapNone }
 
-docbookWithOpts :: ToPandoc a => WriterOptions -> a -> String
-docbookWithOpts opts = unpack . purely (writeDocbook4 opts) . toPandoc
+docbookWithOpts :: ToPandoc a => WriterOptions -> a -> Text
+docbookWithOpts opts = purely (writeDocbook4 opts) . toPandoc
 
 {-
   "my test" =: X =?> Y
@@ -27,15 +27,16 @@ which is in turn shorthand for
 -}
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test docbook
 
 lineblock :: Blocks
 lineblock = para ("some text" <> linebreak <>
                   "and more lines" <> linebreak <>
                   "and again")
-lineblock_out :: [String]
+
+lineblock_out :: [Text]
 lineblock_out = [ "<literallayout>some text"
                 , "and more lines"
                 , "and again</literallayout>"
@@ -304,7 +305,7 @@ tests = [ testGroup "line blocks"
                       <> header 3 (text "header3")
 
               docbookTopLevelDiv :: (ToPandoc a)
-                                 => TopLevelDivision -> a -> String
+                                 => TopLevelDivision -> a -> Text
               docbookTopLevelDiv division =
                 docbookWithOpts def{ writerTopLevelDivision = division }
             in
diff --git a/test/Tests/Writers/FB2.hs b/test/Tests/Writers/FB2.hs
index 2e10636fa..e4ff4d5cc 100644
--- a/test/Tests/Writers/FB2.hs
+++ b/test/Tests/Writers/FB2.hs
@@ -7,13 +7,13 @@ import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
 import Text.Pandoc.Builder
 
-fb2 :: String -> String
-fb2 x = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" ++
-        "<FictionBook xmlns=\"http://www.gribuser.ru/xml/fictionbook/2.0\" xmlns:l=\"http://www.w3.org/1999/xlink\"><description><title-info><genre>unrecognised</genre></title-info><document-info><program-used>pandoc</program-used></document-info></description><body><title><p /></title><section>" ++ x ++ "</section></body></FictionBook>"
+fb2 :: Text -> Text
+fb2 x = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" <>
+        "<FictionBook xmlns=\"http://www.gribuser.ru/xml/fictionbook/2.0\" xmlns:l=\"http://www.w3.org/1999/xlink\"><description><title-info><genre>unrecognised</genre></title-info><document-info><program-used>pandoc</program-used></document-info></description><body><title><p /></title><section>" <> x <> "</section></body></FictionBook>"
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test (purely (writeFB2 def) . toPandoc)
 
 tests :: [TestTree]
diff --git a/test/Tests/Writers/HTML.hs b/test/Tests/Writers/HTML.hs
index 328801e31..5d59fd79b 100644
--- a/test/Tests/Writers/HTML.hs
+++ b/test/Tests/Writers/HTML.hs
@@ -29,8 +29,8 @@ which is in turn shorthand for
 -}
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test html
 
 tests :: [TestTree]
@@ -72,17 +72,17 @@ tests = [ testGroup "inline code"
         , testGroup "sample with style"
           [ "samp should wrap highlighted code" =:
             codeWith ("",["sample","haskell"],[]) ">>="
-            =?> ("<samp><code class=\"sourceCode haskell\">" ++
+            =?> ("<samp><code class=\"sourceCode haskell\">" <>
                 "<span class=\"op\">&gt;&gt;=</span></code></samp>")
           ]
         , testGroup "variable with style"
           [ "var should wrap highlighted code" =:
             codeWith ("",["haskell","variable"],[]) ">>="
-            =?> ("<var><code class=\"sourceCode haskell\">" ++
+            =?> ("<var><code class=\"sourceCode haskell\">" <>
                 "<span class=\"op\">&gt;&gt;=</span></code></var>")
           ]
         ]
         where
-          tQ :: (ToString a, ToPandoc a)
-               => String -> (a, String) -> TestTree
+          tQ :: (ToText a, ToPandoc a)
+               => String -> (a, Text) -> TestTree
           tQ = test htmlQTags
diff --git a/test/Tests/Writers/JATS.hs b/test/Tests/Writers/JATS.hs
index 2f501c890..55a277c6a 100644
--- a/test/Tests/Writers/JATS.hs
+++ b/test/Tests/Writers/JATS.hs
@@ -31,8 +31,8 @@ which is in turn shorthand for
 -}
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test jats
 
 tests :: [TestTree]
diff --git a/test/Tests/Writers/Jira.hs b/test/Tests/Writers/Jira.hs
index 0c6f48853..58abf8bc8 100644
--- a/test/Tests/Writers/Jira.hs
+++ b/test/Tests/Writers/Jira.hs
@@ -13,7 +13,7 @@ jira :: (ToPandoc a) => a -> String
 jira = unpack . purely (writeJira def) . toPandoc
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a, HasCallStack)
+(=:) :: (ToText a, ToPandoc a, HasCallStack)
      => String -> (a, String) -> TestTree
 (=:) = test jira
 
diff --git a/test/Tests/Writers/LaTeX.hs b/test/Tests/Writers/LaTeX.hs
index ae5879099..1ce62487e 100644
--- a/test/Tests/Writers/LaTeX.hs
+++ b/test/Tests/Writers/LaTeX.hs
@@ -33,8 +33,8 @@ which is in turn shorthand for
 -}
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test latex
 
 tests :: [TestTree]
diff --git a/test/Tests/Writers/Markdown.hs b/test/Tests/Writers/Markdown.hs
index d4f927ebe..aea920b9d 100644
--- a/test/Tests/Writers/Markdown.hs
+++ b/test/Tests/Writers/Markdown.hs
@@ -14,11 +14,11 @@ defopts = def
   { writerExtensions = pandocExtensions
   , writerSetextHeaders = True }
 
-markdown :: (ToPandoc a) => a -> String
-markdown = unpack . purely (writeMarkdown defopts) . toPandoc
+markdown :: (ToPandoc a) => a -> Text
+markdown = purely (writeMarkdown defopts) . toPandoc
 
-markdownWithOpts :: (ToPandoc a) => WriterOptions -> a -> String
-markdownWithOpts opts x = unpack . purely (writeMarkdown opts) $ toPandoc x
+markdownWithOpts :: (ToPandoc a) => WriterOptions -> a -> Text
+markdownWithOpts opts x = purely (writeMarkdown opts) $ toPandoc x
 
 {-
   "my test" =: X =?> Y
@@ -33,8 +33,8 @@ which is in turn shorthand for
 -}
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test markdown
 
 tests :: [TestTree]
@@ -182,9 +182,9 @@ noteTests = testGroup "note and reference location"
 shortcutLinkRefsTests :: TestTree
 shortcutLinkRefsTests =
   let infix 4 =:
-      (=:) :: (ToString a, ToPandoc a)
+      (=:) :: (ToText a, ToPandoc a)
 
-        => String -> (a, String) -> TestTree
+        => String -> (a, Text) -> TestTree
       (=:) = test (purely (writeMarkdown defopts{writerReferenceLinks = True}) . toPandoc)
   in testGroup "Shortcut reference links"
      [ "Simple link (shortcutable)"
diff --git a/test/Tests/Writers/Ms.hs b/test/Tests/Writers/Ms.hs
index ad6849633..ce8c712ac 100644
--- a/test/Tests/Writers/Ms.hs
+++ b/test/Tests/Writers/Ms.hs
@@ -7,8 +7,8 @@ import Text.Pandoc
 import Text.Pandoc.Builder
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test (purely (writeMs def . toPandoc))
 
 tests :: [TestTree]
diff --git a/test/Tests/Writers/Muse.hs b/test/Tests/Writers/Muse.hs
index 5bddca3af..c76574682 100644
--- a/test/Tests/Writers/Muse.hs
+++ b/test/Tests/Writers/Muse.hs
@@ -7,7 +7,7 @@ import Test.Tasty
 import Tests.Helpers
 import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
-import Text.Pandoc.Builder
+import Text.Pandoc.Builder as B
 
 defopts :: WriterOptions
 defopts = def{ writerWrapText = WrapPreserve,
@@ -21,7 +21,7 @@ museWithOpts :: (ToPandoc a) => WriterOptions -> a -> Text
 museWithOpts opts = purely (writeMuse opts) . toPandoc
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
+(=:) :: (ToText a, ToPandoc a)
      => String -> (a, Text) -> TestTree
 (=:) = test muse
 
@@ -446,7 +446,7 @@ tests = [ testGroup "block elements"
             , "escape hash to avoid accidental anchors" =: text "#foo bar"
               =?> "<verbatim>#foo</verbatim> bar"
             , "escape definition list markers" =: str "::" =?> "<verbatim>::</verbatim>"
-            , "normalize strings before escaping" =: fromList [Str ":", Str ":"] =?> "<verbatim>::</verbatim>"
+            , "normalize strings before escaping" =: B.fromList [Str ":", Str ":"] =?> "<verbatim>::</verbatim>"
             -- We don't want colons to be escaped if they can't be confused
             -- with definition list item markers.
             , "do not escape colon" =: str ":" =?> ":"
diff --git a/test/Tests/Writers/Native.hs b/test/Tests/Writers/Native.hs
index d7771ca19..b1a8882f1 100644
--- a/test/Tests/Writers/Native.hs
+++ b/test/Tests/Writers/Native.hs
@@ -6,14 +6,15 @@ import Test.Tasty.QuickCheck
 import Tests.Helpers
 import Text.Pandoc
 import Text.Pandoc.Arbitrary ()
+import Text.Pandoc.Shared (safeRead)
 
 p_write_rt :: Pandoc -> Bool
 p_write_rt d =
-  read (unpack $ purely (writeNative def{ writerTemplate = Just mempty }) d) == d
+  safeRead (purely (writeNative def{ writerTemplate = Just mempty }) d) == Just d
 
 p_write_blocks_rt :: [Block] -> Bool
 p_write_blocks_rt bs =
-  read (unpack $ purely (writeNative def) (Pandoc nullMeta bs)) == bs
+  safeRead (purely (writeNative def) (Pandoc nullMeta bs)) == Just bs
 
 tests :: [TestTree]
 tests = [ testProperty "p_write_rt" p_write_rt
diff --git a/test/Tests/Writers/OOXML.hs b/test/Tests/Writers/OOXML.hs
index c1e47622d..ac74a9652 100644
--- a/test/Tests/Writers/OOXML.hs
+++ b/test/Tests/Writers/OOXML.hs
@@ -16,6 +16,7 @@ import Data.Maybe (catMaybes, mapMaybe)
 import Tests.Helpers
 import Data.Algorithm.Diff
 import System.FilePath.Glob (compile, match)
+import qualified Data.Text as T
 
 compareXMLBool :: Content -> Content -> Bool
 -- We make a special exception for times at the moment, and just pass
@@ -41,10 +42,11 @@ compareXMLBool (CRef myStr) (CRef goodStr) =
   myStr == goodStr
 compareXMLBool _ _ = False
 
-displayDiff :: Content -> Content -> String
+displayDiff :: Content -> Content -> Text
 displayDiff elemA elemB =
-  showDiff (1,1)
-    (getDiff (lines $ showContent elemA) (lines $ showContent elemB))
+  T.pack $ showDiff (1,1)
+    (getDiff (lines $ T.pack $ showContent elemA)
+             (lines $ T.pack $ showContent elemB))
 
 goldenArchive :: FilePath -> IO Archive
 goldenArchive fp = toArchive . BL.fromStrict <$> BS.readFile fp
@@ -58,7 +60,7 @@ testArchive writerFn opts fp = do
   bs <- runIOorExplode $ readNative def txt >>= writerFn opts
   return $ toArchive bs
 
-compareFileList :: FilePath -> Archive -> Archive -> Maybe String
+compareFileList :: FilePath -> Archive -> Archive -> Maybe Text
 compareFileList goldenFP goldenArch testArch =
   let testFiles = filesInArchive testArch
       goldenFiles = filesInArchive goldenArch
@@ -69,54 +71,58 @@ compareFileList goldenFP goldenArch testArch =
         [ if null diffGoldenTest
           then Nothing
           else Just $
-               "Files in " ++ goldenFP ++ " but not in generated archive:\n" ++
-               intercalate ", " diffGoldenTest
+               "Files in " <> T.pack goldenFP <>
+               " but not in generated archive:\n" <>
+               T.pack (intercalate ", " diffGoldenTest)
         , if null diffTestGolden
           then Nothing
           else Just $
-               "Files in generated archive but not in " ++ goldenFP ++ ":\n" ++
-               intercalate ", " diffTestGolden
+               "Files in generated archive but not in " <> T.pack goldenFP <>
+               ":\n" <> T.pack (intercalate ", " diffTestGolden)
         ]
   in
     if null $ catMaybes results
     then Nothing
-    else Just $ intercalate "\n" $ catMaybes results
+    else Just $ T.intercalate "\n" $ catMaybes results
 
-compareXMLFile' :: FilePath -> Archive -> Archive -> Either String ()
+compareXMLFile' :: FilePath -> Archive -> Archive -> Either Text ()
 compareXMLFile' fp goldenArch testArch = do
   testEntry <- case findEntryByPath fp testArch of
                  Just entry -> Right entry
                  Nothing -> Left $
-                   "Can't extract " ++ fp ++ " from generated archive"
+                   "Can't extract " <> T.pack fp <> " from generated archive"
   testXMLDoc <- case parseXMLDoc $ fromEntry testEntry of
                   Just doc -> Right doc
                   Nothing -> Left $
-                    "Can't parse xml in  " ++ fp ++ " from generated archive"
+                    "Can't parse xml in  " <> T.pack fp <>
+                    " from generated archive"
 
   goldenEntry <- case findEntryByPath fp goldenArch of
                  Just entry -> Right entry
                  Nothing -> Left $
-                   "Can't extract " ++ fp ++ " from archive in stored file"
+                   "Can't extract " <> T.pack fp <>
+                   " from archive in stored file"
   goldenXMLDoc <- case parseXMLDoc $ fromEntry goldenEntry of
                   Just doc -> Right doc
                   Nothing -> Left $
-                    "Can't parse xml in  " ++ fp ++ " from archive in stored file"
+                    "Can't parse xml in  " <> T.pack fp <>
+                    " from archive in stored file"
 
   let testContent = Elem testXMLDoc
       goldenContent = Elem goldenXMLDoc
 
   if compareXMLBool goldenContent testContent
     then Right ()
-    else Left $
-    "Non-matching xml in " ++ fp ++ ":\n" ++ displayDiff testContent goldenContent
+    else Left $ "Non-matching xml in " <> T.pack fp <> ":\n" <>
+                displayDiff testContent goldenContent
 
-compareXMLFile :: FilePath -> Archive -> Archive -> Maybe String
+compareXMLFile :: FilePath -> Archive -> Archive -> Maybe Text
 compareXMLFile fp goldenArch testArch =
   case compareXMLFile' fp goldenArch testArch of
     Right _ -> Nothing
     Left s -> Just s
 
-compareAllXMLFiles :: Archive -> Archive -> Maybe String
+compareAllXMLFiles :: Archive -> Archive -> Maybe Text
 compareAllXMLFiles goldenArch testArch =
   let allFiles = filesInArchive goldenArch `union` filesInArchive testArch
       allXMLFiles = sort $
@@ -130,29 +136,30 @@ compareAllXMLFiles goldenArch testArch =
     then Nothing
     else Just $ unlines results
 
-compareMediaFile' :: FilePath -> Archive -> Archive -> Either String ()
+compareMediaFile' :: FilePath -> Archive -> Archive -> Either Text ()
 compareMediaFile' fp goldenArch testArch = do
   testEntry <- case findEntryByPath fp testArch of
                  Just entry -> Right entry
                  Nothing -> Left $
-                   "Can't extract " ++ fp ++ " from generated archive"
+                   "Can't extract " <> T.pack fp <> " from generated archive"
   goldenEntry <- case findEntryByPath fp goldenArch of
                  Just entry -> Right entry
                  Nothing -> Left $
-                   "Can't extract " ++ fp ++ " from archive in stored file"
+                   "Can't extract " <> T.pack fp <>
+                   " from archive in stored file"
 
   if fromEntry testEntry == fromEntry goldenEntry
     then Right ()
     else Left $
-    "Non-matching binary file: " ++ fp
+    "Non-matching binary file: " <> T.pack fp
 
-compareMediaFile :: FilePath -> Archive -> Archive -> Maybe String
+compareMediaFile :: FilePath -> Archive -> Archive -> Maybe Text
 compareMediaFile fp goldenArch testArch =
   case compareMediaFile' fp goldenArch testArch of
     Right _ -> Nothing
     Left s -> Just s
 
-compareAllMediaFiles :: Archive -> Archive -> Maybe String
+compareAllMediaFiles :: Archive -> Archive -> Maybe Text
 compareAllMediaFiles goldenArch testArch =
   let allFiles = filesInArchive goldenArch `union` filesInArchive testArch
       mediaPattern = compile "*/media/*"
@@ -181,5 +188,5 @@ ooxmlTest writerFn testName opts nativeFP goldenFP =
                          , compareAllXMLFiles goldenArch testArch
                          , compareAllMediaFiles goldenArch testArch
                          ]
-     in return $ if null res then Nothing else Just $ unlines res)
+     in return $ if null res then Nothing else Just $ T.unpack $ unlines res)
   (\a -> BL.writeFile goldenFP $ fromArchive a)
diff --git a/test/Tests/Writers/Org.hs b/test/Tests/Writers/Org.hs
index bd6c9b7ab..1935861ab 100644
--- a/test/Tests/Writers/Org.hs
+++ b/test/Tests/Writers/Org.hs
@@ -9,7 +9,7 @@ import Text.Pandoc.Arbitrary ()
 import Text.Pandoc.Builder
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
+(=:) :: (ToText a, ToPandoc a)
      => String -> (a, Text) -> TestTree
 (=:) = test org
 
diff --git a/test/Tests/Writers/Plain.hs b/test/Tests/Writers/Plain.hs
index 17edc9dbd..f4c539805 100644
--- a/test/Tests/Writers/Plain.hs
+++ b/test/Tests/Writers/Plain.hs
@@ -9,8 +9,8 @@ import Text.Pandoc.Builder
 
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test (purely (writePlain def{ writerExtensions =
                           enableExtension Ext_gutenberg plainExtensions }) .
                       toPandoc)
diff --git a/test/Tests/Writers/RST.hs b/test/Tests/Writers/RST.hs
index 94745e9a2..64df785a8 100644
--- a/test/Tests/Writers/RST.hs
+++ b/test/Tests/Writers/RST.hs
@@ -12,19 +12,19 @@ import Text.Pandoc.Writers.RST
 import qualified Data.Text as T
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
-     => String -> (a, String) -> TestTree
+(=:) :: (ToText a, ToPandoc a)
+     => String -> (a, Text) -> TestTree
 (=:) = test (purely (writeRST def . toPandoc))
 
-testTemplate :: (ToString a, ToString c, ToPandoc a) =>
+testTemplate :: (ToText a, ToText c, ToPandoc a) =>
                 String -> String -> (a, c) -> TestTree
 testTemplate t = case runIdentity (compileTemplate [] (T.pack t)) of
-    Left e -> error $ "Could not compile RST template: " ++ e
+    Left e -> error $ T.pack $ "Could not compile RST template: " ++ e
     Right templ -> test (purely (writeRST def{ writerTemplate = Just templ }) . toPandoc)
 
 bodyTemplate :: Template T.Text
 bodyTemplate = case runIdentity (compileTemplate [] "$body$\n") of
-                    Left e      -> error $
+                    Left e      -> error $ T.pack $
                       "Could not compile RST bodyTemplate" ++ e
                     Right templ -> templ
 
diff --git a/test/Tests/Writers/TEI.hs b/test/Tests/Writers/TEI.hs
index fa372909f..562b27187 100644
--- a/test/Tests/Writers/TEI.hs
+++ b/test/Tests/Writers/TEI.hs
@@ -20,7 +20,7 @@ which is in turn shorthand for
 -}
 
 infix 4 =:
-(=:) :: (ToString a, ToPandoc a)
+(=:) :: (ToText a, ToPandoc a)
      => String -> (a, String) -> TestTree
 (=:) = test (purely (writeTEI def) . toPandoc)
 
diff --git a/test/fb2/meta.fb2 b/test/fb2/meta.fb2
index 1db48c068..1385949f8 100644
--- a/test/fb2/meta.fb2
+++ b/test/fb2/meta.fb2
@@ -1,3 +1,2 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <FictionBook xmlns="http://www.gribuser.ru/xml/fictionbook/2.0" xmlns:l="http://www.w3.org/1999/xlink"><description><title-info><genre>unrecognised</genre><book-title>Book title</book-title><annotation><p>This is the abstract.</p><p>It consists of two paragraphs.</p></annotation></title-info><document-info><program-used>pandoc</program-used></document-info></description><body><title><p>Book title</p></title></body></FictionBook>
-
diff --git a/test/fb2/titles.fb2 b/test/fb2/titles.fb2
index d7e585902..426cfe892 100644
--- a/test/fb2/titles.fb2
+++ b/test/fb2/titles.fb2
@@ -1,3 +1,2 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <FictionBook xmlns="http://www.gribuser.ru/xml/fictionbook/2.0" xmlns:l="http://www.w3.org/1999/xlink"><description><title-info><genre>unrecognised</genre></title-info><document-info><program-used>pandoc</program-used></document-info></description><body><title><p /></title><section id="simple-title"><title><p>Simple title</p></title><p>This example tests FictionBook titles.</p></section><section id="emphasized-strong-title"><title><p><emphasis>Emphasized</emphasis> <strong>Strong</strong> Title</p></title></section></body></FictionBook>
-