corrupted file tests

tests/pngsuite.nim

@@ -1,4 +1,7 @@
-const pngSuiteFiles* = [
+# http://www.schaik.com/pngsuite/
+
+const
+  pngSuiteFiles* = [
     # Basic
     "basn0g01", # black & white
     "basn0g02", # 2 bit (4 level) grayscale
@@ -70,4 +73,21 @@ const pngSuiteFiles* = [
     "s39n3p04", # 39x39 paletted file, no interlacing
     # "s40i3p04", # 40x40 paletted file, interlaced
     "s40n3p04", # 40x40 paletted file, no interlacing
-]
+  ]
+
+  pngSuiteCorruptedFiles* = [
+    "xs1n0g01", # signature byte 1 MSBit reset to zero
+    "xs2n0g01", # signature byte 2 is a 'Q'
+    "xs4n0g01", # signature byte 4 lowercase
+    "xs7n0g01", # 7th byte a space instead of control-Z
+    "xcrn0g04", # added cr bytes
+    "xlfn0g04", # added lf bytes
+    # "xhdn0g08", # incorrect IHDR checksum
+    "xc1n0g08", # color type 1
+    "xc9n2c08", # color type 9
+    "xd0n2c08", # bit-depth 0
+    "xd3n2c08", # bit-depth 3
+    "xd9n2c08", # bit-depth 99
+    "xdtn0g01", # missing IDAT chunk
+    # "xcsn0g01" # incorrect IDAT checksum
+  ]

tests/test_png.nim

@@ -1,4 +1,4 @@
-import pixie/fileformats/png, strformat, pngsuite
+import pixie/fileformats/png, strformat, pngsuite, pixie/common
 
 for file in pngSuiteFiles:
   let
@@ -20,3 +20,10 @@ for channels in 1 .. 4:
           components[i] = (x * 16).uint8
         data.add(components)
   let encoded = encodePng(16, 16, channels, data[0].addr, data.len)
+
+for file in pngSuiteCorruptedFiles:
+  try:
+    discard decodePng(readFile(&"tests/data/pngsuite/{file}.png"))
+    doAssert false
+  except PixieError:
+    discard