diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,10 @@
 # ChangeLog for yesod-test
 
+## 1.6.10
+
+* `statusIs` assertion failures now print a preview of the response body, if the response body is UTF-8 or ASCII. [#1680](https://github.com/yesodweb/yesod/pull/1680/files)
+* Adds an `Yesod.Test.Internal`, which exposes functions that yesod-test uses. These functions do _not_ constitute a stable API.
+
 ## 1.6.9.1
 
 * Improve documentation [#1676](https://github.com/yesodweb/yesod/pull/1676)
diff --git a/Yesod/Test.hs b/Yesod/Test.hs
--- a/Yesod/Test.hs
+++ b/Yesod/Test.hs
@@ -249,7 +249,6 @@
 import Yesod.Core.Unsafe (runFakeHandler)
 import Yesod.Test.TransversingCSS
 import Yesod.Core
-import Yesod.Core.Json (contentTypeHeaderIsJson)
 import qualified Data.Text.Lazy as TL
 import Data.Text.Lazy.Encoding (encodeUtf8, decodeUtf8, decodeUtf8With)
 import Text.XML.Cursor hiding (element)
@@ -279,6 +278,8 @@
 import Data.Aeson (FromJSON, eitherDecode')
 import Control.Monad (unless)
 
+import Yesod.Test.Internal (getBodyTextPreview, contentTypeHeaderIsUtf8)
+
 {-# DEPRECATED byLabel "This function seems to have multiple bugs (ref: https://github.com/yesodweb/yesod/pull/1459). Use byLabelExact, byLabelContain, byLabelPrefix or byLabelSuffix instead" #-}
 {-# DEPRECATED fileByLabel "This function seems to have multiple bugs (ref: https://github.com/yesodweb/yesod/pull/1459). Use fileByLabelExact, fileByLabelContain, fileByLabelPrefix or fileByLabelSuffix instead" #-}
 
@@ -569,18 +570,26 @@
 assertEqualNoShow msg a b = liftIO $ HUnit.assertBool msg (a == b)
 
 -- | Assert the last response status is as expected.
+-- If the status code doesn't match, a portion of the body is also printed to aid in debugging.
 --
 -- ==== __Examples__
 --
 -- > get HomeR
 -- > statusIs 200
 statusIs :: HasCallStack => Int -> YesodExample site ()
-statusIs number = withResponse $ \ SResponse { simpleStatus = s } ->
-  liftIO $ flip HUnit.assertBool (H.statusCode s == number) $ concat
-    [ "Expected status was ", show number
-    , " but received status was ", show $ H.statusCode s
-    ]
+statusIs number = do
+  withResponse $ \(SResponse status headers body) -> do
+    let mContentType = lookup hContentType headers
+        isUTF8ContentType = maybe False contentTypeHeaderIsUtf8 mContentType
 
+    liftIO $ flip HUnit.assertBool (H.statusCode status == number) $ concat
+      [ "Expected status was ", show number
+      , " but received status was ", show $ H.statusCode status
+      , if isUTF8ContentType
+          then ". For debugging, the body was: " <> (T.unpack $ getBodyTextPreview body)
+          else ""
+      ]
+
 -- | Assert the given header key/value pair was returned.
 --
 -- ==== __Examples__
@@ -774,13 +783,7 @@
         isJSONContentType
         (failure $ T.pack $ "Expected `Content-Type: application/json` in the headers, got: " ++ show headers)
     case eitherDecode' body of
-        Left err -> do
-          let characterLimit = 1024
-              textBody = TL.toStrict $ decodeUtf8 body
-              bodyPreview = if T.length textBody < characterLimit
-                then textBody
-                else T.take characterLimit textBody <> "... (use `printBody` to see complete response body)"
-          failure $ T.concat ["Failed to parse JSON response; error: ", T.pack err, "JSON: ", bodyPreview]
+        Left err -> failure $ T.concat ["Failed to parse JSON response; error: ", T.pack err, "JSON: ", getBodyTextPreview body]
         Right v -> return v
 
 -- | Outputs the last response body to stderr (So it doesn't get captured by HSpec). Useful for debugging.
diff --git a/Yesod/Test/Internal.hs b/Yesod/Test/Internal.hs
new file mode 100644
--- /dev/null
+++ b/Yesod/Test/Internal.hs
@@ -0,0 +1,65 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+-- | This module exposes functions that are used internally by yesod-test.
+-- The functions exposed here are _not_ a stable API—they may be changed or removed without any major version bump.
+--
+-- That said, you may find them useful if your application can accept API breakage.
+module Yesod.Test.Internal
+  ( getBodyTextPreview
+  , contentTypeHeaderIsUtf8
+  , assumedUTF8ContentTypes
+  ) where
+
+import qualified Data.ByteString.Char8 as BS8
+import qualified Data.ByteString.Lazy as LBS
+import qualified Data.Set as Set
+import qualified Data.Text as T
+import qualified Data.Text.Encoding as TE
+import qualified Data.Text.Lazy as TL
+import qualified Data.Text.Lazy.Encoding as DTLE
+import qualified Yesod.Core.Content as Content
+import Data.Semigroup (Semigroup(..))
+
+-- | Helper function to get the first 1024 characters of the body, assuming it is UTF-8.
+-- This function is used to preview the body in case of an assertion failure.
+--
+-- @since 1.6.10
+getBodyTextPreview :: LBS.ByteString -> T.Text
+getBodyTextPreview body =
+  let characterLimit = 1024
+      textBody = TL.toStrict $ DTLE.decodeUtf8 body
+  in if T.length textBody < characterLimit
+        then textBody
+        else T.take characterLimit textBody <> "... (use `printBody` to see complete response body)"
+
+-- | Helper function to determine if we can print a body as plain text, for debugging purposes.
+--
+-- @since 1.6.10
+contentTypeHeaderIsUtf8 :: BS8.ByteString -> Bool
+contentTypeHeaderIsUtf8 contentTypeBS =
+      -- Convert to Text, so we can use T.splitOn
+  let contentTypeText = T.toLower $ TE.decodeUtf8 contentTypeBS
+      isUTF8FromCharset = case T.splitOn "charset=" contentTypeText of
+        -- Either a specific designation as UTF-8, or ASCII (which is a subset of UTF-8)
+        [_, charSet] -> any (`T.isInfixOf` charSet) ["utf-8", "us-ascii"]
+        _ -> False
+
+      isInferredUTF8FromContentType = BS8.takeWhile (/= ';') contentTypeBS `Set.member` assumedUTF8ContentTypes
+
+  in isUTF8FromCharset || isInferredUTF8FromContentType
+
+-- | List of Content-Types that are assumed to be UTF-8 (e.g. JSON).
+--
+-- @since 1.6.10
+assumedUTF8ContentTypes :: Set.Set BS8.ByteString
+assumedUTF8ContentTypes = Set.fromList $ map Content.simpleContentType
+  [ Content.typeHtml
+  , Content.typePlain
+  , Content.typeJson
+  , Content.typeXml
+  , Content.typeAtom
+  , Content.typeRss
+  , Content.typeSvg
+  , Content.typeJavascript
+  , Content.typeCss
+  ]
diff --git a/test/main.hs b/test/main.hs
--- a/test/main.hs
+++ b/test/main.hs
@@ -45,6 +45,7 @@
 import qualified Web.Cookie as Cookie
 import Data.Maybe (isNothing)
 import qualified Data.Text as T
+import Yesod.Test.Internal (contentTypeHeaderIsUtf8)
 
 parseQuery_ :: Text -> [[SelectorGroup]]
 parseQuery_ = either error id . parseQuery
@@ -125,6 +126,19 @@
                         ]
                     ]
              in HD.parseLBS html @?= doc
+    describe "identifying text-based bodies" $ do
+        it "matches content-types with an explicit UTF-8 charset" $ do
+            contentTypeHeaderIsUtf8 "application/custom; charset=UTF-8" @?= True
+            contentTypeHeaderIsUtf8 "application/custom; charset=utf-8" @?= True
+        it "matches content-types with an ASCII charset" $ do
+            contentTypeHeaderIsUtf8 "application/custom; charset=us-ascii" @?= True
+        it "matches content-types that we assume are UTF-8" $ do
+            contentTypeHeaderIsUtf8 "text/html" @?= True
+            contentTypeHeaderIsUtf8 "application/json" @?= True
+        it "doesn't match content-type headers that are binary data" $ do
+            contentTypeHeaderIsUtf8 "image/gif" @?= False
+            contentTypeHeaderIsUtf8 "application/pdf" @?= False
+
     describe "basic usage" $ yesodSpec app $ do
         ydescribe "tests1" $ do
             yit "tests1a" $ do
diff --git a/yesod-test.cabal b/yesod-test.cabal
--- a/yesod-test.cabal
+++ b/yesod-test.cabal
@@ -1,5 +1,5 @@
 name:               yesod-test
-version:            1.6.9.1
+version:            1.6.10
 license:            MIT
 license-file:       LICENSE
 author:             Nubis <nubis@woobiz.com.ar>
@@ -45,6 +45,7 @@
     exposed-modules: Yesod.Test
                      Yesod.Test.CssQuery
                      Yesod.Test.TransversingCSS
+                     Yesod.Test.Internal
     ghc-options:  -Wall
 
 test-suite test