add test for defining new placeholder

tests/test_jdog.py

@@ -1,5 +1,8 @@
+import re
+
 import jdog as jd
 from jdog.placeholder.name import NamePlaceholder
+from jdog.placeholder.placeholder import FuncStrPlaceholder, FuncPlaceholder
 
 
 def test_parse_basic():
@@ -24,4 +27,22 @@ def name_placeholder(_):
     jdog.parse_scheme(scheme)
     monkeypatch.setattr(NamePlaceholder, 'exec', name_placeholder)
 
-    assert jdog.generate() == '{"name":"John Doe"}'
+    assert jdog.generate() == '{"name":"John Doe"}'
+
+
+def test_add_new():
+    scheme = """{"f":"{{test}}"}"""
+
+    def match(token):
+        return re.match(r'^{{test}}$', token)
+
+    jdog = jd.Jdog()
+    jdog.add_matcher('test', match, lambda tok,arg: FuncStrPlaceholder(tok,arg, lambda _: 'foo'))
+
+    jdog.parse_scheme(scheme)
+    res = jdog.generate()
+
+    assert res == """{"f":"foo"}"""
+
+
+