diff --git a/tests/test_wadler.py b/tests/test_wadler.py
new file mode 100644
index 0000000..2327f91
--- /dev/null
+++ b/tests/test_wadler.py
@@ -0,0 +1,137 @@
+import typing
+
+from parser.parser import Grammar, Re, Terminal, rule, opt
+
+import parser.runtime as runtime
+import parser.wadler as wadler
+
+
+class JsonGrammar(Grammar):
+    start = "root"
+
+    trivia = ["BLANKS"]
+
+    @rule
+    def root(self):
+        return self.value
+
+    @rule(transparent=True)
+    def value(self):
+        return (
+            self.object
+            | self.array
+            | self.NUMBER
+            | self.TRUE
+            | self.FALSE
+            | self.NULL
+            | self.STRING
+        )
+
+    @rule
+    def object(self):
+        return self.LCURLY + opt(self._object_pairs) + self.RCURLY
+
+    @rule
+    def _object_pairs(self):
+        return self.object_pair | (self._object_pairs + self.COMMA + self.object_pair)
+
+    @rule
+    def object_pair(self):
+        return self.STRING + self.COLON + self.value
+
+    @rule
+    def array(self):
+        return self.LSQUARE + opt(self._array_items) + self.RSQUARE
+
+    @rule
+    def _array_items(self):
+        return self.value | (self._array_items + self.COMMA + self.value)
+
+    BLANKS = Terminal(Re.set(" ", "\t", "\r", "\n").plus())
+    LCURLY = Terminal("{")
+    RCURLY = Terminal("}")
+    COMMA = Terminal(",")
+    COLON = Terminal(":")
+    LSQUARE = Terminal("[")
+    RSQUARE = Terminal("]")
+    TRUE = Terminal("true")
+    FALSE = Terminal("false")
+    NULL = Terminal("null")
+    NUMBER = Terminal(
+        Re.seq(
+            Re.set(("0", "9")).plus(),
+            Re.seq(
+                Re.literal("."),
+                Re.set(("0", "9")).plus(),
+            ).question(),
+            Re.seq(
+                Re.set("e", "E"),
+                Re.set("+", "-").question(),
+                Re.set(("0", "9")).plus(),
+            ).question(),
+        ),
+    )
+    STRING = Terminal(
+        Re.seq(
+            Re.literal('"'),
+            (~Re.set('"', "\\") | (Re.set("\\") + Re.any())).star(),
+            Re.literal('"'),
+        )
+    )
+
+
+JSON = JsonGrammar()
+JSON_TABLE = JSON.build_table()
+JSON_LEXER = JSON.compile_lexer()
+JSON_PARSER = runtime.Parser(JSON_TABLE)
+
+
+def flatten_document(doc: wadler.Document, src: str) -> list:
+    match doc:
+        case wadler.NewLine():
+            return ["\n"]
+        case wadler.Indent():
+            return [f"<indent {doc.amount}>", flatten_document(doc.doc, src)]
+        case wadler.Text(start, end):
+            return [src[start:end]]
+        case wadler.Group():
+            return [flatten_document(doc.child, src)]
+        case wadler.Lazy():
+            return flatten_document(doc.resolve(), src)
+        case wadler.Cons():
+            return flatten_document(doc.left, src) + flatten_document(doc.right, src)
+        case None:
+            return []
+        case _:
+            typing.assert_never(doc)
+
+
+def test_basic_printer():
+    text = '{"a": true, "b":[1,2,3]}'
+    tokens = runtime.GenericTokenStream(text, JSON_LEXER)
+    tree, errors = JSON_PARSER.parse(tokens)
+    assert [] == errors
+    assert tree is not None
+
+    printer = wadler.Printer(JSON)
+    doc = flatten_document(printer.convert_tree_to_document(tree), text)
+
+    assert doc == [
+        "{",
+        '"a"',
+        ":",
+        "true",
+        ",",
+        '"b"',
+        ":",
+        "[",
+        "1",
+        ",",
+        "2",
+        ",",
+        "3",
+        "]",
+        "}",
+    ]
+
+    pass