vm/tests: restore JSON tests parsing

Make sure we support new test format. Tests itself will be restored
later.

pkg/vm/json_test.go

@@ -94,7 +94,6 @@ const (
 )
 
 func TestUT(t *testing.T) {
-	t.Skip()
 	testsRan := false
 	err := filepath.Walk(testsDir, func(path string, info os.FileInfo, err error) error {
 		if !strings.HasSuffix(path, ".json") {
@@ -124,12 +123,25 @@ func testFile(t *testing.T, filename string) {
 	data, err := ioutil.ReadFile(filename)
 	require.NoError(t, err)
 
+	// get rid of possible BOM
+	if len(data) > 2 && data[0] == 0xef && data[1] == 0xbb && data[2] == 0xbf {
+		data = data[3:]
+	}
+	if strings.HasSuffix(filename, "MEMCPY.json") {
+		return // FIXME not a valid JSON https://github.com/neo-project/neo-vm/issues/322
+	}
+
 	ut := new(vmUT)
-	require.NoError(t, json.Unmarshal(data, ut))
+	require.NoErrorf(t, json.Unmarshal(data, ut), "file: %s", filename)
+	return
 
 	t.Run(ut.Category+":"+ut.Name, func(t *testing.T) {
+		isRot := strings.HasSuffix(filename, "ROT.json")
 		for i := range ut.Tests {
 			test := ut.Tests[i]
+			if isRot && test.Name == "Without push" {
+				return // FIXME #927 single ROT is interpreted as PUSH1
+			}
 			t.Run(ut.Tests[i].Name, func(t *testing.T) {
 				prog := []byte(test.Script)
 				vm := load(prog)