diff --git a/docs/Examples/Image/Main.purs b/docs/Examples/Image/Main.purs
index f48882b..2b96fe9 100644
--- a/docs/Examples/Image/Main.purs
+++ b/docs/Examples/Image/Main.purs
@@ -20,8 +20,7 @@ filePath = "./docs/Examples/Image/circle.png"
 
 -- | Respond with image data when run
 image :: HTTPure.Request -> HTTPure.ResponseM
-image _ =
-  FS.readFile filePath >>= HTTPure.binaryResponse' 200 headers
+image _ = FS.readFile filePath >>= HTTPure.ok' headers
   where
     headers = HTTPure.header "Content-Type" "image/png"
 
diff --git a/src/HTTPure.purs b/src/HTTPure.purs
index 51464da..e9699c8 100644
--- a/src/HTTPure.purs
+++ b/src/HTTPure.purs
@@ -20,7 +20,6 @@ import HTTPure.Response
   ( Response
   , ResponseM
   , response, response'
-  , binaryResponse, binaryResponse'
   , emptyResponse, emptyResponse'
 
   -- 1xx
diff --git a/src/HTTPure/Body.purs b/src/HTTPure/Body.purs
index 73413e1..5e68dc6 100644
--- a/src/HTTPure/Body.purs
+++ b/src/HTTPure/Body.purs
@@ -1,13 +1,14 @@
 module HTTPure.Body
-  ( Body(..)
+  ( class Body
   , read
-  , write
   , size
+  , write
   ) where
 
 import Prelude
 
 import Data.Either as Either
+import Data.Maybe as Maybe
 import Effect as Effect
 import Effect.Aff as Aff
 import Effect.Ref as Ref
@@ -16,11 +17,44 @@ import Node.Encoding as Encoding
 import Node.HTTP as HTTP
 import Node.Stream as Stream
 
--- | The `Body` type is just sugar for a `String`, that will be sent or received
--- | in the HTTP body.
-data Body
-  = StringBody String
-  | BinaryBody Buffer.Buffer
+-- | Types that implement the `Body` class can be used as a body to an HTTPure
+-- | response, and can be used with all the response helpers.
+class Body b where
+
+  -- | Given a body value, return an effect that maybe calculates a size.
+  -- | TODO: This is a `Maybe` to support chunked transfer encoding.  We still
+  -- | need to add code to send the body using chunking if the effect resolves a
+  -- | `Maybe.Nothing`.
+  size :: b -> Effect.Effect (Maybe.Maybe Int)
+
+  -- | Given a body value and a Node HTTP `Response` value, write the body value
+  -- | to the Node response.
+  write :: b -> HTTP.Response -> Aff.Aff Unit
+
+-- | The instance for `String` will convert the string to a buffer first in
+-- | order to determine it's size.  This is to properly handle UTF-8 characters
+-- | in the string.  Writing is simply implemented by writing the string to the
+-- | response stream and closing the response stream.
+instance bodyString :: Body String where
+  size body = Buffer.fromString body Encoding.UTF8 >>= size
+  write body response = Aff.makeAff \done -> do
+    let stream = HTTP.responseAsStream response
+    _ <- Stream.writeString stream Encoding.UTF8 body $ pure unit
+    _ <- Stream.end stream $ pure unit
+    done $ Either.Right unit
+    pure Aff.nonCanceler
+
+-- | The instance for `Buffer` is trivial--to calculate size, we use
+-- | `Buffer.size`, and to send the response, we just write the buffer to the
+-- | stream and end the stream.
+instance bodyBuffer :: Body Buffer.Buffer where
+  size = Buffer.size >>> map Maybe.Just
+  write body response = Aff.makeAff \done -> do
+    let stream = HTTP.responseAsStream response
+    _ <- Stream.write stream body $ pure unit
+    _ <- Stream.end stream $ pure unit
+    done $ Either.Right unit
+    pure Aff.nonCanceler
 
 -- | Extract the contents of the body of the HTTP `Request`.
 read :: HTTP.Request -> Aff.Aff String
@@ -30,21 +64,4 @@ read request = Aff.makeAff \done -> do
   Stream.onDataString stream Encoding.UTF8 \str ->
     void $ Ref.modify ((<>) str) buf
   Stream.onEnd stream $ Ref.read buf >>= Either.Right >>> done
-  pure $ Aff.nonCanceler
-
--- | Write a `Body` to the given HTTP `Response` and close it.
-write :: HTTP.Response -> Body -> Effect.Effect Unit
-write response body = void do
-  _ <- writeToStream $ pure unit
-  Stream.end stream $ pure unit
-  where
-    stream = HTTP.responseAsStream response
-    writeToStream =
-      case body of
-        StringBody str -> Stream.writeString stream Encoding.UTF8 str
-        BinaryBody buf -> Stream.write stream buf
-
--- | Get the size of the body in bytes
-size :: Body -> Effect.Effect Int
-size (StringBody body) = Buffer.fromString body Encoding.UTF8 >>= Buffer.size
-size (BinaryBody body) = Buffer.size body
+  pure Aff.nonCanceler
diff --git a/src/HTTPure/Headers.purs b/src/HTTPure/Headers.purs
index 9e48bed..d2dcd13 100644
--- a/src/HTTPure/Headers.purs
+++ b/src/HTTPure/Headers.purs
@@ -1,5 +1,5 @@
 module HTTPure.Headers
-  ( Headers
+  ( Headers(..)
   , empty
   , headers
   , header
@@ -11,6 +11,7 @@ import Prelude
 
 import Effect as Effect
 import Foreign.Object as Object
+import Data.Newtype as Newtype
 import Data.String as String
 import Data.TraversableWithIndex as TraversableWithIndex
 import Data.Tuple as Tuple
@@ -22,6 +23,7 @@ import HTTPure.Lookup ((!!))
 -- | The `Headers` type is just sugar for a `Object` of `Strings`
 -- | that represents the set of headers in an HTTP request or response.
 newtype Headers = Headers (Object.Object String)
+derive instance newtypeHeaders :: Newtype.Newtype Headers _
 
 -- | Given a string, return a `Maybe` containing the value of the matching
 -- | header, if there is any.
@@ -50,9 +52,7 @@ read = HTTP.requestHeaders >>> Headers
 
 -- | Given an HTTP `Response` and a `Headers` object, return an effect that will
 -- | write the `Headers` to the `Response`.
-write :: HTTP.Response ->
-         Headers ->
-         Effect.Effect Unit
+write :: HTTP.Response -> Headers -> Effect.Effect Unit
 write response (Headers headers') = void $
   TraversableWithIndex.traverseWithIndex (HTTP.setHeader response) headers'
 
diff --git a/src/HTTPure/Lookup.purs b/src/HTTPure/Lookup.purs
index a9ac71e..d765f5d 100644
--- a/src/HTTPure/Lookup.purs
+++ b/src/HTTPure/Lookup.purs
@@ -16,7 +16,7 @@ import Foreign.Object as Object
 -- | retrieve some value. For instance, you could have an implementation for
 -- | `String Int String` where `lookup s i` returns `Just` a `String` containing
 -- | the character in `s` at `i`, or `Nothing` if `i` is out of bounds.
-class Lookup c k r where
+class Lookup c k r | c -> r where
 
   -- | Given some type and a key on that type, extract some value that
   -- | corresponds to that key.
diff --git a/src/HTTPure/Response.purs b/src/HTTPure/Response.purs
index f72ee19..79ed777 100644
--- a/src/HTTPure/Response.purs
+++ b/src/HTTPure/Response.purs
@@ -3,7 +3,6 @@ module HTTPure.Response
   , ResponseM
   , send
   , response, response'
-  , binaryResponse, binaryResponse'
   , emptyResponse, emptyResponse'
 
   -- 1xx
@@ -79,9 +78,9 @@ module HTTPure.Response
 
 import Prelude
 
-import Effect as Effect
+import Data.Maybe as Maybe
 import Effect.Aff as Aff
-import Node.Buffer as Buffer
+import Effect.Class as EffectClass
 import Node.HTTP as HTTP
 
 import HTTPure.Body as Body
@@ -97,45 +96,37 @@ type ResponseM = Aff.Aff Response
 type Response =
   { status :: Status.Status
   , headers :: Headers.Headers
-  , body :: Body.Body
+  , writeBody :: HTTP.Response -> Aff.Aff Unit
+  , size :: Maybe.Maybe Int
   }
 
 -- | Given an HTTP `Response` and a HTTPure `Response`, this method will return
 -- | a monad encapsulating writing the HTTPure `Response` to the HTTP `Response`
 -- | and closing the HTTP `Response`.
-send :: HTTP.Response -> Response -> Effect.Effect Unit
-send httpresponse { status, headers, body } = do
-  Status.write httpresponse $ status
-  size <- Body.size body
-  Headers.write httpresponse $ headers <> contentLength size
-  Body.write httpresponse $ body
+send :: HTTP.Response -> Response -> Aff.Aff Unit
+send httpresponse { status, headers, writeBody, size } = do
+  EffectClass.liftEffect $ Status.write httpresponse status
+  EffectClass.liftEffect $ Headers.write httpresponse finalHeaders
+  writeBody httpresponse
   where
-    contentLength size = Headers.header "Content-Length" $ show size
+    finalHeaders = headers <> contentLength size
+    contentLength (Maybe.Just s) = Headers.header "Content-Length" $ show s
+    contentLength Maybe.Nothing = Headers.empty
 
 -- | For custom response statuses or providing a body for response codes that
 -- | don't typically send one.
-response :: Status.Status -> String -> ResponseM
+response :: forall b. Body.Body b => Status.Status -> b -> ResponseM
 response status = response' status Headers.empty
 
 -- | The same as `response` but with headers.
-response' :: Status.Status ->
+response' :: forall b. Body.Body b =>
+             Status.Status ->
              Headers.Headers ->
-             String ->
+             b ->
              ResponseM
-response' status headers body =
-  pure $ { status, headers, body: Body.StringBody body }
-
--- | Like `response`, but the response body is binary data.
-binaryResponse :: Status.Status -> Buffer.Buffer -> Aff.Aff Response
-binaryResponse status = binaryResponse' status Headers.empty
-
--- | The same as `binaryResponse` but with headers.
-binaryResponse' :: Status.Status ->
-                   Headers.Headers ->
-                   Buffer.Buffer ->
-                   Aff.Aff Response
-binaryResponse' status headers body
-  = pure $ { status, headers, body: Body.BinaryBody body }
+response' status headers body = do
+  size <- EffectClass.liftEffect $ Body.size body
+  pure $ { status, headers, size, writeBody: Body.write body }
 
 -- | The same as `response` but without a body.
 emptyResponse :: Status.Status -> ResponseM
@@ -178,11 +169,11 @@ processing' = emptyResponse' Status.processing
 ---------
 
 -- | 200
-ok :: String -> ResponseM
+ok :: forall b. Body.Body b => b -> ResponseM
 ok = ok' Headers.empty
 
 -- | 200 with headers
-ok' :: Headers.Headers -> String -> ResponseM
+ok' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 ok' = response' Status.ok
 
 -- | 201
@@ -202,12 +193,13 @@ accepted' :: Headers.Headers -> ResponseM
 accepted' = emptyResponse' Status.accepted
 
 -- | 203
-nonAuthoritativeInformation :: String -> ResponseM
+nonAuthoritativeInformation :: forall b. Body.Body b => b -> ResponseM
 nonAuthoritativeInformation = nonAuthoritativeInformation' Headers.empty
 
 -- | 203 with headers
-nonAuthoritativeInformation' :: Headers.Headers ->
-                                String ->
+nonAuthoritativeInformation' :: forall b. Body.Body b =>
+                                Headers.Headers ->
+                                b ->
                                 ResponseM
 nonAuthoritativeInformation' = response' Status.nonAuthoritativeInformation
 
@@ -228,19 +220,19 @@ resetContent' :: Headers.Headers -> ResponseM
 resetContent' = emptyResponse' Status.resetContent
 
 -- | 206
-partialContent :: String -> ResponseM
+partialContent :: forall b. Body.Body b => b -> ResponseM
 partialContent = partialContent' Headers.empty
 
 -- | 206 with headers
-partialContent' :: Headers.Headers -> String -> ResponseM
+partialContent' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 partialContent' = response' Status.partialContent
 
 -- | 207
-multiStatus :: String -> ResponseM
+multiStatus :: forall b. Body.Body b => b -> ResponseM
 multiStatus = multiStatus' Headers.empty
 
 -- | 207 with headers
-multiStatus' :: Headers.Headers -> String -> ResponseM
+multiStatus' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 multiStatus' = response' Status.multiStatus
 
 -- | 208
@@ -252,11 +244,11 @@ alreadyReported' :: Headers.Headers -> ResponseM
 alreadyReported' = emptyResponse' Status.alreadyReported
 
 -- | 226
-iMUsed :: String -> ResponseM
+iMUsed :: forall b. Body.Body b => b -> ResponseM
 iMUsed = iMUsed' Headers.empty
 
 -- | 226 with headers
-iMUsed' :: Headers.Headers -> String -> ResponseM
+iMUsed' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 iMUsed' = response' Status.iMUsed
 
 ---------
@@ -264,35 +256,35 @@ iMUsed' = response' Status.iMUsed
 ---------
 
 -- | 300
-multipleChoices :: String -> ResponseM
+multipleChoices :: forall b. Body.Body b => b -> ResponseM
 multipleChoices = multipleChoices' Headers.empty
 
 -- | 300 with headers
-multipleChoices' :: Headers.Headers -> String -> ResponseM
+multipleChoices' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 multipleChoices' = response' Status.multipleChoices
 
 -- | 301
-movedPermanently :: String -> ResponseM
+movedPermanently :: forall b. Body.Body b => b -> ResponseM
 movedPermanently = movedPermanently' Headers.empty
 
 -- | 301 with headers
-movedPermanently' :: Headers.Headers -> String -> ResponseM
+movedPermanently' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 movedPermanently' = response' Status.movedPermanently
 
 -- | 302
-found :: String -> ResponseM
+found :: forall b. Body.Body b => b -> ResponseM
 found = found' Headers.empty
 
 -- | 302 with headers
-found' :: Headers.Headers -> String -> ResponseM
+found' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 found' = response' Status.found
 
 -- | 303
-seeOther :: String -> ResponseM
+seeOther :: forall b. Body.Body b => b -> ResponseM
 seeOther = seeOther' Headers.empty
 
 -- | 303 with headers
-seeOther' :: Headers.Headers -> String -> ResponseM
+seeOther' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 seeOther' = response' Status.seeOther
 
 -- | 304
@@ -304,27 +296,27 @@ notModified' :: Headers.Headers -> ResponseM
 notModified' = emptyResponse' Status.notModified
 
 -- | 305
-useProxy :: String -> ResponseM
+useProxy :: forall b. Body.Body b => b -> ResponseM
 useProxy = useProxy' Headers.empty
 
 -- | 305 with headers
-useProxy' :: Headers.Headers -> String -> ResponseM
+useProxy' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 useProxy' = response' Status.useProxy
 
 -- | 307
-temporaryRedirect :: String -> ResponseM
+temporaryRedirect :: forall b. Body.Body b => b -> ResponseM
 temporaryRedirect = temporaryRedirect' Headers.empty
 
 -- | 307 with headers
-temporaryRedirect' :: Headers.Headers -> String -> ResponseM
+temporaryRedirect' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 temporaryRedirect' = response' Status.temporaryRedirect
 
 -- | 308
-permanentRedirect :: String -> ResponseM
+permanentRedirect :: forall b. Body.Body b => b -> ResponseM
 permanentRedirect = permanentRedirect' Headers.empty
 
 -- | 308 with headers
-permanentRedirect' :: Headers.Headers -> String -> ResponseM
+permanentRedirect' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 permanentRedirect' = response' Status.permanentRedirect
 
 
@@ -333,11 +325,11 @@ permanentRedirect' = response' Status.permanentRedirect
 ---------
 
 -- | 400
-badRequest :: String -> ResponseM
+badRequest :: forall b. Body.Body b => b -> ResponseM
 badRequest = badRequest' Headers.empty
 
 -- | 400 with headers
-badRequest' :: Headers.Headers -> String -> ResponseM
+badRequest' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 badRequest' = response' Status.badRequest
 
 -- | 401
@@ -405,11 +397,11 @@ requestTimeout' :: Headers.Headers -> ResponseM
 requestTimeout' = emptyResponse' Status.requestTimeout
 
 -- | 409
-conflict :: String -> ResponseM
+conflict :: forall b. Body.Body b => b -> ResponseM
 conflict = conflict' Headers.empty
 
 -- | 409 with headers
-conflict' :: Headers.Headers -> String -> ResponseM
+conflict' :: forall b. Body.Body b => Headers.Headers -> b -> ResponseM
 conflict' = response' Status.conflict
 
 -- | 410
@@ -561,11 +553,14 @@ unavailableForLegalReasons' = emptyResponse' Status.unavailableForLegalReasons
 ---------
 
 -- | 500
-internalServerError :: String -> ResponseM
+internalServerError :: forall b. Body.Body b => b -> ResponseM
 internalServerError = internalServerError' Headers.empty
 
 -- | 500 with headers
-internalServerError' :: Headers.Headers -> String -> ResponseM
+internalServerError' :: forall b. Body.Body b =>
+                        Headers.Headers ->
+                        b ->
+                        ResponseM
 internalServerError' = response' Status.internalServerError
 
 -- | 501
diff --git a/src/HTTPure/Server.purs b/src/HTTPure/Server.purs
index a75334e..48261b1 100644
--- a/src/HTTPure/Server.purs
+++ b/src/HTTPure/Server.purs
@@ -10,7 +10,6 @@ import Prelude
 
 import Effect as Effect
 import Effect.Aff as Aff
-import Effect.Class as EffectClass
 import Data.Maybe as Maybe
 import Data.Options ((:=), Options)
 import Node.Encoding as Encoding
@@ -37,7 +36,7 @@ handleRequest :: (Request.Request -> Response.ResponseM) ->
 handleRequest router request response =
   void $ Aff.runAff (\_ -> pure unit) do
     req <- Request.fromHTTPRequest request
-    router req >>= Response.send response >>> EffectClass.liftEffect
+    router req >>= Response.send response
 
 -- | Given a `ListenOptions` object, a function mapping `Request` to
 -- | `ResponseM`, and a `ServerM` containing effects to run on boot, creates and
diff --git a/test/Test/HTTPure/BodySpec.purs b/test/Test/HTTPure/BodySpec.purs
index a54dcab..3e5cf9e 100644
--- a/test/Test/HTTPure/BodySpec.purs
+++ b/test/Test/HTTPure/BodySpec.purs
@@ -2,6 +2,7 @@ module Test.HTTPure.BodySpec where
 
 import Prelude
 
+import Data.Maybe as Maybe
 import Effect.Class as EffectClass
 import Node.Buffer as Buffer
 import Node.Encoding as Encoding
@@ -21,28 +22,37 @@ readSpec = Spec.describe "read" do
 
 sizeSpec :: TestHelpers.Test
 sizeSpec = Spec.describe "size" do
-  Spec.it "returns the correct size for ASCII string body" do
-    size <- EffectClass.liftEffect $ Body.size $ Body.StringBody "ascii"
-    size ?= 5
-
-  Spec.it "returns the correct size for UTF-8 string body" do
-    size <- EffectClass.liftEffect $ Body.size $ Body.StringBody "\x2603"  -- snowman
-    size ?= 3
-
-  Spec.it "returns the correct size for binary body" do
-    size <- EffectClass.liftEffect do
-      buf <- Buffer.fromString "foobar" Encoding.UTF8
-      Body.size $ Body.BinaryBody buf
-    size ?= 6
+  Spec.describe "String" do
+    Spec.it "returns the correct size for ASCII string body" do
+      size <- EffectClass.liftEffect $ Body.size "ascii"
+      size ?= Maybe.Just 5
+    Spec.it "returns the correct size for UTF-8 string body" do
+      size <- EffectClass.liftEffect $ Body.size "\x2603"  -- snowman
+      size ?= Maybe.Just 3
+  Spec.describe "Buffer" do
+    Spec.it "returns the correct size for binary body" do
+      size <- EffectClass.liftEffect do
+        buf <- Buffer.fromString "foobar" Encoding.UTF8
+        Body.size buf
+      size ?= Maybe.Just 6
 
 writeSpec :: TestHelpers.Test
 writeSpec = Spec.describe "write" do
-  Spec.it "writes the string to the Response body" do
-    body <- EffectClass.liftEffect do
-      resp <- TestHelpers.mockResponse
-      Body.write resp $ Body.StringBody "test"
-      pure $ TestHelpers.getResponseBody resp
-    body ?= "test"
+  Spec.describe "String" do
+    Spec.it "writes the String to the Response body" do
+      body <- do
+        resp <- EffectClass.liftEffect TestHelpers.mockResponse
+        Body.write "test" resp
+        pure $ TestHelpers.getResponseBody resp
+      body ?= "test"
+  Spec.describe "Buffer" do
+    Spec.it "writes the Buffer to the Response body" do
+      body <- do
+        resp <- EffectClass.liftEffect TestHelpers.mockResponse
+        buf <- EffectClass.liftEffect $ Buffer.fromString "test" Encoding.UTF8
+        Body.write buf resp
+        pure $ TestHelpers.getResponseBody resp
+      body ?= "test"
 
 bodySpec :: TestHelpers.Test
 bodySpec = Spec.describe "Body" do
diff --git a/test/Test/HTTPure/HTTPureEffectsSpec.purs b/test/Test/HTTPure/HTTPureEffectsSpec.purs
deleted file mode 100644
index 73f9acc..0000000
--- a/test/Test/HTTPure/HTTPureEffectsSpec.purs
+++ /dev/null
@@ -1,11 +0,0 @@
-module Test.HTTPure.HTTPureEffectsSpec where
-
-import Prelude
-
-import Test.Spec as Spec
-
-import Test.HTTPure.TestHelpers as TestHelpers
-
-httpureEffectsSpec :: TestHelpers.Test
-httpureEffectsSpec = Spec.describe "HTTPureEffects" do
-  pure unit
diff --git a/test/Test/HTTPure/LookupSpec.purs b/test/Test/HTTPure/LookupSpec.purs
index 1cdb157..302e3eb 100644
--- a/test/Test/HTTPure/LookupSpec.purs
+++ b/test/Test/HTTPure/LookupSpec.purs
@@ -30,23 +30,22 @@ hasSpec = Spec.describe "has" do
     Spec.it "is false" do
       [ "one", "two", "three" ] !? 4 ?= false
 
-lookupArraySpec :: TestHelpers.Test
-lookupArraySpec = Spec.describe "lookupArray" do
-  Spec.describe "when the index is in bounds" do
-    Spec.it "is Just the value at the index" do
-      [ "one", "two", "three" ] !! 1 ?= Maybe.Just "two"
-  Spec.describe "when the index is out of bounds" do
-    Spec.it "is Nothing" do
-      (([ "one", "two", "three" ] !! 4) :: Maybe.Maybe String) ?= Maybe.Nothing
-
-lookupMapSpec :: TestHelpers.Test
-lookupMapSpec = Spec.describe "lookupMap" do
-  Spec.describe "when the key is in the Map" do
-    Spec.it "is Just the value at the given key" do
-      mockMap !! "foo" ?= Maybe.Just "bar"
-  Spec.describe "when the key is not in the Map" do
-    Spec.it "is Nothing" do
-      ((mockMap !! "baz") :: Maybe.Maybe String) ?= Maybe.Nothing
+lookupFunctionSpec :: TestHelpers.Test
+lookupFunctionSpec = Spec.describe "lookup" do
+  Spec.describe "Array" do
+    Spec.describe "when the index is in bounds" do
+      Spec.it "is Just the value at the index" do
+        [ "one", "two", "three" ] !! 1 ?= Maybe.Just "two"
+    Spec.describe "when the index is out of bounds" do
+      Spec.it "is Nothing" do
+        (([ "one", "two", "three" ] !! 4) :: Maybe.Maybe String) ?= Maybe.Nothing
+  Spec.describe "Map" do
+    Spec.describe "when the key is in the Map" do
+      Spec.it "is Just the value at the given key" do
+        mockMap !! "foo" ?= Maybe.Just "bar"
+    Spec.describe "when the key is not in the Map" do
+      Spec.it "is Nothing" do
+        ((mockMap !! "baz") :: Maybe.Maybe String) ?= Maybe.Nothing
   where
     mockMap = Object.singleton "foo" "bar"
 
@@ -54,5 +53,4 @@ lookupSpec :: TestHelpers.Test
 lookupSpec = Spec.describe "Lookup" do
   atSpec
   hasSpec
-  lookupArraySpec
-  lookupMapSpec
+  lookupFunctionSpec
diff --git a/test/Test/HTTPure/ResponseSpec.purs b/test/Test/HTTPure/ResponseSpec.purs
index 2ff5e6f..d02e08e 100644
--- a/test/Test/HTTPure/ResponseSpec.purs
+++ b/test/Test/HTTPure/ResponseSpec.purs
@@ -2,13 +2,15 @@ module Test.HTTPure.ResponseSpec where
 
 import Prelude
 
+import Data.Either as Either
+import Data.Maybe as Maybe
+import Effect.Aff as Aff
 import Effect.Class as EffectClass
-import Node.Buffer as Buffer
 import Node.Encoding as Encoding
+import Node.HTTP as HTTP
+import Node.Stream as Stream
 import Test.Spec as Spec
-import Test.Spec.Assertions as Assertions
 
-import HTTPure.Body as Body
 import HTTPure.Headers as Headers
 import HTTPure.Response as Response
 
@@ -18,35 +20,41 @@ import Test.HTTPure.TestHelpers ((?=))
 sendSpec :: TestHelpers.Test
 sendSpec = Spec.describe "send" do
   Spec.it "writes the headers" do
-    header <- EffectClass.liftEffect do
-      httpResponse <- TestHelpers.mockResponse
-      Response.send httpResponse mockResponse
+    header <- do
+      httpResponse <- EffectClass.liftEffect $ TestHelpers.mockResponse
+      Response.send httpResponse $ mockResponse unit
       pure $ TestHelpers.getResponseHeader "Test" httpResponse
     header ?= "test"
   Spec.it "sets the Content-Length header" do
-    header <- EffectClass.liftEffect do
-      httpResponse <- TestHelpers.mockResponse
-      Response.send httpResponse mockResponse
+    header <- do
+      httpResponse <- EffectClass.liftEffect $ TestHelpers.mockResponse
+      Response.send httpResponse $ mockResponse unit
       pure $ TestHelpers.getResponseHeader "Content-Length" httpResponse
     header ?= "4"
   Spec.it "writes the status" do
-    status <- EffectClass.liftEffect do
-      httpResponse <- TestHelpers.mockResponse
-      Response.send httpResponse mockResponse
+    status <- do
+      httpResponse <- EffectClass.liftEffect $ TestHelpers.mockResponse
+      Response.send httpResponse $ mockResponse unit
       pure $ TestHelpers.getResponseStatus httpResponse
     status ?= 123
   Spec.it "writes the body" do
-    body <- EffectClass.liftEffect do
-      httpResponse <- TestHelpers.mockResponse
-      Response.send httpResponse mockResponse
+    body <- do
+      httpResponse <- EffectClass.liftEffect $ TestHelpers.mockResponse
+      Response.send httpResponse $ mockResponse unit
       pure $ TestHelpers.getResponseBody httpResponse
     body ?= "test"
   where
     mockHeaders = Headers.header "Test" "test"
-    mockResponse =
+    mockResponse _ =
       { status: 123
       , headers: mockHeaders
-      , body: Body.StringBody "test"
+      , writeBody: \response -> Aff.makeAff \done -> do
+          stream <- pure $ HTTP.responseAsStream response
+          _ <- Stream.writeString stream Encoding.UTF8 "test" $ pure unit
+          _ <- Stream.end stream $ pure unit
+          done $ Either.Right unit
+          pure Aff.nonCanceler
+      , size: Maybe.Just 4
       }
 
 responseFunctionSpec :: TestHelpers.Test
@@ -57,11 +65,16 @@ responseFunctionSpec = Spec.describe "response" do
   Spec.it "has empty headers" do
     resp <- Response.response 123 "test"
     resp.headers ?= Headers.empty
-  Spec.it "has the right body" do
+  Spec.it "has the right size" do
     resp <- Response.response 123 "test"
-    case resp.body of
-      Body.StringBody str -> str ?= "test"
-      _ -> Assertions.fail "String body expected"
+    resp.size ?= Maybe.Just 4
+  Spec.it "has the right writeBody function" do
+    body <- do
+      resp <- Response.response 123 "test"
+      httpResponse <- EffectClass.liftEffect $ TestHelpers.mockResponse
+      resp.writeBody httpResponse
+      pure $ TestHelpers.getResponseBody httpResponse
+    body ?= "test"
 
 response'Spec :: TestHelpers.Test
 response'Spec = Spec.describe "response'" do
@@ -71,56 +84,20 @@ response'Spec = Spec.describe "response'" do
   Spec.it "has the right headers" do
     resp <- mockResponse
     resp.headers ?= mockHeaders
-  Spec.it "has the right body" do
+  Spec.it "has the right size" do
     resp <- mockResponse
-    case resp.body of
-      Body.StringBody str -> str ?= "test"
-      _ -> Assertions.fail "String body expected"
+    resp.size ?= Maybe.Just 4
+  Spec.it "has the right writeBody function" do
+    body <- do
+      resp <- mockResponse
+      httpResponse <- EffectClass.liftEffect $ TestHelpers.mockResponse
+      resp.writeBody httpResponse
+      pure $ TestHelpers.getResponseBody httpResponse
+    body ?= "test"
   where
     mockHeaders = Headers.header "Test" "test"
     mockResponse = Response.response' 123 mockHeaders "test"
 
-binaryResponseSpec :: TestHelpers.Test
-binaryResponseSpec = Spec.describe "binaryResponse" do
-  Spec.it "has the right status" do
-    body <- EffectClass.liftEffect $ Buffer.fromString "test" Encoding.UTF8
-    resp <- Response.binaryResponse 123 body
-    resp.status ?= 123
-  Spec.it "has empty headers" do
-    body <- EffectClass.liftEffect $ Buffer.fromString "test" Encoding.UTF8
-    resp <- Response.binaryResponse 123 body
-    resp.headers ?= Headers.empty
-  Spec.it "has the right body" do
-    body <- EffectClass.liftEffect $ Buffer.fromString "test" Encoding.UTF8
-    resp <- Response.binaryResponse 123 body
-    case resp.body of
-      Body.BinaryBody bin -> do
-        str <- EffectClass.liftEffect $ Buffer.toString Encoding.UTF8 bin
-        str ?= "test"
-      _ -> Assertions.fail "Binary body expected"
-
-binaryResponse'Spec :: TestHelpers.Test
-binaryResponse'Spec = Spec.describe "binaryResponse'" do
-  Spec.it "has the right status" do
-    body <- EffectClass.liftEffect $ Buffer.fromString "test" Encoding.UTF8
-    resp <- mockResponse body
-    resp.status ?= 123
-  Spec.it "has the right headers" do
-    body <- EffectClass.liftEffect $ Buffer.fromString "test" Encoding.UTF8
-    resp <- mockResponse body
-    resp.headers ?= mockHeaders
-  Spec.it "has the right body" do
-    body <- EffectClass.liftEffect $ Buffer.fromString "test" Encoding.UTF8
-    resp <- mockResponse body
-    case resp.body of
-      Body.BinaryBody bin -> do
-        str <- EffectClass.liftEffect $ Buffer.toString Encoding.UTF8 bin
-        str ?= "test"
-      _ -> Assertions.fail "Binary body expected"
-  where
-    mockHeaders = Headers.header "Test" "test"
-    mockResponse = Response.binaryResponse' 123 mockHeaders
-
 emptyResponseSpec :: TestHelpers.Test
 emptyResponseSpec = Spec.describe "emptyResponse" do
   Spec.it "has the right status" do
@@ -129,11 +106,16 @@ emptyResponseSpec = Spec.describe "emptyResponse" do
   Spec.it "has empty headers" do
     resp <- Response.emptyResponse 123
     resp.headers ?= Headers.empty
-  Spec.it "has an empty body" do
+  Spec.it "has the right size" do
     resp <- Response.emptyResponse 123
-    case resp.body of
-      Body.StringBody str -> str ?= ""
-      _ -> Assertions.fail "String body expected"
+    resp.size ?= Maybe.Just 0
+  Spec.it "has the right writeBody function" do
+    body <- do
+      resp <- Response.emptyResponse 123
+      httpResponse <- EffectClass.liftEffect $ TestHelpers.mockResponse
+      resp.writeBody httpResponse
+      pure $ TestHelpers.getResponseBody httpResponse
+    body ?= ""
 
 emptyResponse'Spec :: TestHelpers.Test
 emptyResponse'Spec = Spec.describe "emptyResponse'" do
@@ -143,11 +125,16 @@ emptyResponse'Spec = Spec.describe "emptyResponse'" do
   Spec.it "has the right headers" do
     resp <- mockResponse
     resp.headers ?= mockHeaders
-  Spec.it "has an empty body" do
+  Spec.it "has the right size" do
     resp <- mockResponse
-    case resp.body of
-      Body.StringBody str -> str ?= ""
-      _ -> Assertions.fail "String body expected"
+    resp.size ?= Maybe.Just 0
+  Spec.it "has the right writeBody function" do
+    body <- do
+      resp <- mockResponse
+      httpResponse <- EffectClass.liftEffect $ TestHelpers.mockResponse
+      resp.writeBody httpResponse
+      pure $ TestHelpers.getResponseBody httpResponse
+    body ?= ""
   where
     mockHeaders = Headers.header "Test" "test"
     mockResponse = Response.emptyResponse' 123 mockHeaders
@@ -157,7 +144,5 @@ responseSpec = Spec.describe "Response" do
   sendSpec
   responseFunctionSpec
   response'Spec
-  binaryResponseSpec
-  binaryResponse'Spec
   emptyResponseSpec
   emptyResponse'Spec
diff --git a/test/Test/HTTPure/TestHelpers.purs b/test/Test/HTTPure/TestHelpers.purs
index 66035fc..a52bbc3 100644
--- a/test/Test/HTTPure/TestHelpers.purs
+++ b/test/Test/HTTPure/TestHelpers.purs
@@ -66,7 +66,7 @@ toBuffer response = Aff.makeAff \done -> do
     Ref.read chunks
     >>= List.reverse >>> Array.fromFoldable >>> Buffer.concat
     >>= Either.Right >>> done
-  pure $ Aff.nonCanceler
+  pure Aff.nonCanceler
 
 -- | Convert a request to an Aff containing the string with the response body.
 toString :: HTTPClient.Response -> Aff.Aff String
@@ -143,8 +143,7 @@ mockRequest method url body =
   EffectClass.liftEffect <<< mockRequestImpl method url body <<< Object.fromFoldable
 
 -- | Mock an HTTP Response object
-foreign import mockResponse ::
-  Effect.Effect HTTP.Response
+foreign import mockResponse :: Effect.Effect HTTP.Response
 
 -- | Get the current body from an HTTP Response object (note this will only work
 -- | with an object returned from mockResponse).
diff --git a/test/Test/Main.purs b/test/Test/Main.purs
index 205a606..71b68b1 100644
--- a/test/Test/Main.purs
+++ b/test/Test/Main.purs
@@ -8,7 +8,6 @@ import Test.Spec.Runner as Runner
 
 import Test.HTTPure.BodySpec as BodySpec
 import Test.HTTPure.HeadersSpec as HeadersSpec
-import Test.HTTPure.HTTPureEffectsSpec as HTTPureEffectsSpec
 import Test.HTTPure.LookupSpec as LookupSpec
 import Test.HTTPure.MethodSpec as MethodSpec
 import Test.HTTPure.PathSpec as PathSpec
@@ -25,7 +24,6 @@ main :: TestHelpers.TestSuite
 main = Runner.run [ Reporter.specReporter ] $ Spec.describe "HTTPure" do
   BodySpec.bodySpec
   HeadersSpec.headersSpec
-  HTTPureEffectsSpec.httpureEffectsSpec
   LookupSpec.lookupSpec
   MethodSpec.methodSpec
   PathSpec.pathSpec