Use unittest and no longer possible crash on unhandled exception

tests/rlp/util/json_testing.nim

@@ -1,5 +1,5 @@
 import
-  json, strutils, eth/rlp
+  json, strutils, unittest, eth/rlp
 
 proc append(output: var RlpWriter, js: JsonNode) =
   case js.kind
@@ -25,37 +25,32 @@ proc `==`(lhs: JsonNode, rhs: string): bool =
 proc runTests*(filename: string) =
   let js = json.parseFile(filename)
 
+  suite filename:
     for testname, testdata in js:
-    template testStatus(status: string) =
-      echo status, " ", filename, " :: ", testname
-
+      test testname:
         let
           input = testdata{"in"}
           output = testdata{"out"}
 
         if input.isNil or output.isNil or output.kind != JString:
-      testStatus "IGNORED"
+          skip()
           continue
 
         if input == "VALID":
           var rlp = rlpFromHex(output.str)
           discard rlp.inspect
         elif input == "INVALID":
-      var success = false
+          var success = true
           var inspectOutput = ""
-      try:
+          expect MalformedRlpError, UnsupportedRlpError, ValueError:
             var rlp = rlpFromHex(output.str)
             inspectOutput = rlp.inspect(1)
             discard rlp.getType
             while rlp.hasData: discard rlp.toNodes
-      except MalformedRlpError, UnsupportedRlpError, ValueError:
-        success = true
+            success = false
           if not success:
-        testStatus "FAILED"
             echo "  ACCEPTED MALFORMED BYTES: ", output.str
             echo "  INTERPRETATION:\n", inspectOutput
-        program_result = 1
-        continue
         else:
           if input.kind == JString and input.str.len != 0 and input.str[0] == '#':
             continue
@@ -65,12 +60,5 @@ proc runTests*(filename: string) =
           let
             actual = outRlp.finish.hexRepr
             expected = output.str
-      if actual != expected:
-        testStatus "FAILED"
-        echo "  EXPECTED BYTES: ", expected
-        echo "  ACTUAL   BYTES: ", actual
-        program_result = 1
-        continue
-
-    testStatus "OK"
+          check actual == expected