diff --git a/nimPNG.nimble b/nimPNG.nimble
index 4a2354c..42fe99e 100644
--- a/nimPNG.nimble
+++ b/nimPNG.nimble
@@ -13,3 +13,7 @@ task tests, "Run tests":
     exec "nim c -r test.nim"
     exec "nim c -r testCodec.nim"
     exec "nim c -r testSuite.nim"
+    
+    exec "nim c -r -d:release test.nim"
+    exec "nim c -r -d:release testCodec.nim"
+    exec "nim c -r -d:release testSuite.nim"
diff --git a/tester/testSuite.nim b/tester/testSuite.nim
index d85af31..c89954b 100644
--- a/tester/testSuite.nim
+++ b/tester/testSuite.nim
@@ -1,6 +1,6 @@
 import streams, os, strutils, nimPNG, minibmp
 
-proc loadPNG(fileName: string): BMP =
+proc loadPNG2BMP(fileName: string): BMP =
   var settings = makePNGDecoder()
   settings.readTextChunks = true
   var png = loadPNG24(fileName, settings)
@@ -13,7 +13,7 @@ proc loadPNG(fileName: string): BMP =
     result.data[px + 1] = png.data[px + 1]
     result.data[px + 2] = png.data[px + 2]
 
-proc write(bmp: BMP): string =
+proc toString(bmp: BMP): string =
   var s = newStringStream()
   s.writeBMP(bmp)
   result = s.data
@@ -30,9 +30,9 @@ proc convert(dir: string) =
     let bmpName = path.dir & DirSep & path.name & ExtSep & "bmp"
 
     echo fileName, " vs. ", bmpName
-    var bmp = loadPNG(fileName)
+    var bmp = loadPNG2BMP(fileName)
     if bmp != nil:
-      let data1 = bmp.write()
+      let data1 = bmp.toString()
       let data2 = readFile(bmpName)
       assert data1 == data2