Added a number of tests from JSON_checker's test suite here: http://json.org/JSON_checker/

test/fails/1.json

@@ -0,0 +1 @@
+"A JSON payload should be an object or array, not a string."

test/fails/10.json

@@ -0,0 +1 @@
+{"Extra value after close": true} "misplaced quoted value"

test/fails/11.json

@@ -0,0 +1 @@
+{"Illegal expression": 1 + 2}

test/fails/12.json

@@ -0,0 +1 @@
+{"Illegal invocation": alert()}

test/fails/13.json

@@ -0,0 +1 @@
+{"Numbers cannot have leading zeroes": 013}

test/fails/14.json

@@ -0,0 +1 @@
+{"Numbers cannot be hex": 0x14}

test/fails/15.json

@@ -0,0 +1 @@
+["Illegal backslash escape: \x15"]

test/fails/16.json

@@ -0,0 +1 @@
+[\naked]

test/fails/17.json

@@ -0,0 +1 @@
+["Illegal backslash escape: \017"]

test/fails/18.json

@@ -0,0 +1 @@
+[[[[[[[[[[[[[[[[[[[["Too deep"]]]]]]]]]]]]]]]]]]]]

test/fails/19.json

@@ -0,0 +1 @@
+{"Missing colon" null}

test/fails/2.json

@@ -0,0 +1 @@
+["Unclosed array"

test/fails/20.json

@@ -0,0 +1 @@
+{"Double colon":: null}

test/fails/21.json

@@ -0,0 +1 @@
+{"Comma instead of colon", null}

test/fails/22.json

@@ -0,0 +1 @@
+["Colon instead of comma": false]

test/fails/23.json

@@ -0,0 +1 @@
+["Bad value", truth]

test/fails/24.json

@@ -0,0 +1 @@
+['single quote']

test/fails/25.json

@@ -0,0 +1 @@
+["	tab	character	in	string	"]

test/fails/26.json

@@ -0,0 +1 @@
+["tab\   character\   in\  string\  "]

test/fails/27.json

@@ -0,0 +1,2 @@
+["line
+break"]

test/fails/28.json

@@ -0,0 +1,2 @@
+["line\
+break"]

test/fails/29.json

@@ -0,0 +1 @@
+[0e]

test/fails/3.json

@@ -0,0 +1 @@
+{unquoted_key: "keys must be quoted"}

test/fails/30.json

@@ -0,0 +1 @@
+[0e+]

test/fails/31.json

@@ -0,0 +1 @@
+[0e+-1]

test/fails/32.json

@@ -0,0 +1 @@
+{"Comma instead if closing brace": true,

test/fails/33.json

@@ -0,0 +1 @@
+["mismatch"}

test/fails/4.json

@@ -0,0 +1 @@
+["extra comma",]

test/fails/5.json

@@ -0,0 +1 @@
+["double extra comma",,]

test/fails/6.json

@@ -0,0 +1 @@
+[   , "<-- missing value"]

test/fails/7.json

@@ -0,0 +1 @@
+["Comma after the close"],

test/fails/8.json

@@ -0,0 +1 @@
+["Extra close"]]

test/fails/9.json

@@ -0,0 +1 @@
+{"Extra comma": true,}