dfilter: Add some more syntax tests

CMakeLists.txt

@@ -3607,6 +3607,7 @@ set(_test_group_list
 	suite_dfilter.group_scanner
 	suite_dfilter.group_string_type
 	suite_dfilter.group_stringz
+	suite_dfilter.group_syntax
 	suite_dfilter.group_time_relative
 	suite_dfilter.group_time_type
 	suite_dfilter.group_tvb

test/suite_dfilter/group_syntax.py

@@ -0,0 +1,28 @@
+# Copyright (c) 2013 by Gilbert Ramirez <gram@alumni.rice.edu>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+import unittest
+import fixtures
+from suite_dfilter.dfiltertest import *
+
+
+@fixtures.uses_fixtures
+class case_syntax(unittest.TestCase):
+    trace_file = "http.pcap"
+
+    def test_exists_1(self, checkDFilterCount):
+        dfilter = "frame"
+        checkDFilterCount(dfilter, 1)
+
+    def test_commute_1(self, checkDFilterCount):
+        dfilter = "ip.proto == 6"
+        checkDFilterCount(dfilter, 1)
+
+    def test_commute_2(self, checkDFilterCount):
+        dfilter = "6 == ip.proto"
+        checkDFilterCount(dfilter, 1)
+
+    def test_func_1(self, checkDFilterCount):
+        dfilter = "len(frame) == 207"
+        checkDFilterCount(dfilter, 1)