Improve tests for fillMediaBag/extractMedia.

Ensure that the current directory is not changed up if a test fails,
and fix messages for the assertion failures.

test/Tests/MediaBag.hs

@@ -7,16 +7,15 @@ import Test.Tasty.HUnit
 import Text.Pandoc.Class.IO (extractMedia)
 import Text.Pandoc.Class (fillMediaBag, runIOorExplode)
 import System.IO.Temp (withTempDirectory)
+import Text.Pandoc.Shared (inDirectory)
 import System.FilePath
 import Text.Pandoc.Builder as B
-import System.Directory (doesFileExist, copyFile, setCurrentDirectory, getCurrentDirectory)
+import System.Directory (doesFileExist, copyFile)
 
 tests :: [TestTree]
 tests = [
   testCase "test fillMediaBag & extractMedia" $
-      withTempDirectory "." "extractMediaTest" $ \tmpdir -> do
-        olddir <- getCurrentDirectory
-        setCurrentDirectory tmpdir
+      withTempDirectory "." "extractMediaTest" $ \tmpdir -> inDirectory tmpdir $ do
         copyFile "../../test/lalune.jpg" "moon.jpg"
         let d = B.doc $
                   B.para (B.image "../../test/lalune.jpg" "" mempty) <>
@@ -27,14 +26,13 @@ tests = [
           fillMediaBag d
           extractMedia "foo" d
         exists1 <- doesFileExist ("foo" </> "moon.jpg")
-        assertBool "file in directory extract with original name" exists1
+        assertBool "file in directory is not extracted with original name" exists1
         exists2 <- doesFileExist ("foo" </> "f9d88c3dbe18f6a7f5670e994a947d51216cdf0e.jpg")
-        assertBool "file above directory extracted with hashed name" exists2
+        assertBool "file above directory is not extracted with hashed name" exists2
         exists3 <- doesFileExist ("foo" </> "2a0eaa89f43fada3e6c577beea4f2f8f53ab6a1d.lua")
         exists4 <- doesFileExist "a.lua"
-        assertBool "data uri with malicious payload does not get written to arbitrary location"
+        assertBool "data uri with malicious payload gets written outside of destination dir"
           (exists3 && not exists4)
         exists5 <- doesFileExist ("foo" </> "d5fceb6532643d0d84ffe09c40c481ecdf59e15a.gif")
-        assertBool "data uri with gif is properly decoded" exists5
-        setCurrentDirectory olddir
+        assertBool "data uri with gif is not properly decoded" exists5
   ]