diff --git a/src/pyalibert/forward.py b/src/pyalibert/forward.py
index 9e2e7a7..9742283 100644
--- a/src/pyalibert/forward.py
+++ b/src/pyalibert/forward.py
@@ -1,3 +1,4 @@
+from dataclasses import dataclass
 from typing import Generic, Optional, TypeVar
 
 from .transformer import Transformer
@@ -6,6 +7,7 @@ from .parser import Parser
 
 
 P = TypeVar("P")
+@dataclass
 class FutureTransform(Transformer[P]):
     actual: Optional[Transformer[P]]
     def __init__(self) -> None:
@@ -24,16 +26,16 @@ class FutureTransform(Transformer[P]):
 
 P = TypeVar("P")
 class Declare(Generic[P]):
-    parser: Parser[P]
+    parser_: Parser[P]
     transform: FutureTransform[P]
 
     def __init__(self) -> None:
         transform = FutureTransform[P]()
-        self.parser = Parser(transform)
+        self.parser_ = Parser(transform)
         self.transform = transform
 
-    def p(self):
-        return self.parser
+    def parser(self):
+        return self.parser_
 
     def define(self, parser: Parser[P]):
         self.transform.define(parser.inner)
diff --git a/src/pyalibert/transformers/and_.py b/src/pyalibert/transformers/and_.py
index 4b7dca2..08381dd 100644
--- a/src/pyalibert/transformers/and_.py
+++ b/src/pyalibert/transformers/and_.py
@@ -9,9 +9,8 @@ L = TypeVar("L")
 R = TypeVar("R")
 @dataclass
 class AndTransform(Transformer[tuple[L, R]]):
-    def __init__(self, left: Transformer[L], right: Transformer[R]):
-        self.left = left
-        self.right = right
+    left: Transformer[L]
+    right: Transformer[R]
 
     def parse(self, stream: str, at_index: int) -> Result[tuple[L, R]]:
         result_left = self.left.parse(stream, at_index)
@@ -21,3 +20,26 @@ class AndTransform(Transformer[tuple[L, R]]):
         if isinstance(result_right, Failure):
             return result_right
         return Success((result_left.value, result_right.value), result_right.next_index)
+
+
+from okipy.lib import test
+from .just import JustTransform
+
+
+@test()
+def test_and_simple(ctx):
+    parser = AndTransform(JustTransform("ar"), JustTransform("bre"))
+    input = "arbre"
+    assert parser.parse(input, 0) == Success(("ar", "bre"), 5)
+
+@test()
+def test_and_shifted(ctx):
+    parser = AndTransform(JustTransform("ar"), JustTransform("bre"))
+    input = "..arbre..."
+    assert parser.parse(input, 2) == Success(("ar", "bre"), 7)
+
+@test()
+def test_and_none(ctx):
+    parser = AndTransform(JustTransform("ar"), JustTransform("bre"))
+    input = "......"
+    assert parser.parse(input, 2) == Failure(2, set(["ar"]))
diff --git a/src/pyalibert/transformers/end.py b/src/pyalibert/transformers/end.py
index cbab0bf..7f083f4 100644
--- a/src/pyalibert/transformers/end.py
+++ b/src/pyalibert/transformers/end.py
@@ -12,4 +12,26 @@ class EndTransform(Transformer[None]):
     def parse(self, stream: str, at_index: int) -> Result[None]:
         if len(stream) == at_index:
             return Success(None, at_index)
-        return Failure(at_index, set("<end>"))
+        return Failure(at_index, set(["<end>"]))
+
+
+from okipy.lib import test
+
+
+@test()
+def test_end_simple(ctx):
+    parser = EndTransform()
+    input = ""
+    assert parser.parse(input, 0) == Success(None, 0)
+
+@test()
+def test_end_shifted(ctx):
+    parser = EndTransform()
+    input = ".."
+    assert parser.parse(input, 2) == Success(None, 2)
+
+@test()
+def test_end_fails(ctx):
+    parser = EndTransform()
+    input = "arbre......"
+    assert parser.parse(input, 2) == Failure(2, set(["<end>"]))
diff --git a/src/pyalibert/transformers/just.py b/src/pyalibert/transformers/just.py
index b0b462b..5d66eed 100644
--- a/src/pyalibert/transformers/just.py
+++ b/src/pyalibert/transformers/just.py
@@ -6,14 +6,33 @@ from ..transformer import Transformer
 
 @dataclass
 class JustTransform(Transformer[str]):
-    def __init__(self, word: str):
-        self.word = word
-        self.word_len = len(self.word)
+    word: str
 
     def parse(self, stream: str, at_index: int) -> Result[str]:
-        end_index = at_index + self.word_len
+        end_index = at_index + len(self.word)
         prefix = stream[at_index:end_index]
         if prefix == self.word:
             return Success(self.word, end_index)
         return Failure(at_index, set([self.word]))
 
+
+from okipy.lib import test
+
+
+@test()
+def test_just_simple(ctx):
+    parser = JustTransform("arbre")
+    input = "arbre"
+    assert parser.parse(input, 0) == Success("arbre", 5)
+
+@test()
+def test_just_shifted(ctx):
+    parser = JustTransform("arbre")
+    input = "..arbre..."
+    assert parser.parse(input, 2) == Success("arbre", 7)
+
+@test()
+def test_just_fails(ctx):
+    parser = JustTransform("arbre")
+    input = "arbre......"
+    assert parser.parse(input, 2) == Failure(2, set(["arbre"]))
diff --git a/src/pyalibert/transformers/list.py b/src/pyalibert/transformers/list.py
index b9e870c..0171c7d 100644
--- a/src/pyalibert/transformers/list.py
+++ b/src/pyalibert/transformers/list.py
@@ -8,8 +8,7 @@ from ..transformer import Transformer
 T = TypeVar("T")
 @dataclass
 class ListTransform(Transformer[list[T]]):
-    def __init__(self, item: Transformer[T]):
-        self.item = item
+    item: Transformer[T]
 
     def parse(self, stream: str, at_index: int) -> Result[list[T]]:
         values = list[T]()
@@ -22,3 +21,26 @@ class ListTransform(Transformer[list[T]]):
                 raise Exception("Parsing empty patterns repeatedly.")
             at_index = result.next_index
         return Success(values, at_index)
+
+
+from okipy.lib import test
+from .just import JustTransform
+
+
+@test()
+def test_list_simple(ctx):
+    parser = ListTransform(JustTransform("arbre"))
+    input = "arbrearbrearbre"
+    assert parser.parse(input, 0) == Success(["arbre", "arbre", "arbre"], 15)
+
+@test()
+def test_list_shifted(ctx):
+    parser = ListTransform(JustTransform("arbre"))
+    input = "..arbrearbre"
+    assert parser.parse(input, 2) == Success(["arbre", "arbre"], 12)
+
+@test()
+def test_list_none(ctx):
+    parser = ListTransform(JustTransform("arbre"))
+    input = "......"
+    assert parser.parse(input, 2) == Success([], 2)
diff --git a/src/pyalibert/transformers/map.py b/src/pyalibert/transformers/map.py
index 37b0e03..ef9c87f 100644
--- a/src/pyalibert/transformers/map.py
+++ b/src/pyalibert/transformers/map.py
@@ -1,5 +1,5 @@
 from dataclasses import dataclass
-from typing import Callable, TypeVar
+from typing import Callable, Generic, TypeVar
 
 from ..result import Result, Success, Failure
 from ..transformer import Transformer
@@ -8,8 +8,10 @@ from ..transformer import Transformer
 I = TypeVar("I")
 O = TypeVar("O")
 @dataclass
-class MapTransform(Transformer[O]):
-    def __init__(self, value: Transformer[I], transform: Callable[[I], O]):
+class MapTransform(Generic[I, O], Transformer[O]):
+    value: Transformer[I]
+
+    def __init__(self, value: Transformer[I], transform: Callable[[I], O]) -> None:
         self.value = value
         self.transform = transform
 
@@ -19,3 +21,26 @@ class MapTransform(Transformer[O]):
             return result
         transformed = self.transform(result.value)
         return Success(transformed, result.next_index)
+
+
+from okipy.lib import test
+from .just import JustTransform
+
+
+@test()
+def test_map_simple(ctx):
+    parser = MapTransform(JustTransform("arbre"), lambda a: (9, a))
+    input = "arbre"
+    assert parser.parse(input, 0) == Success((9, "arbre"), 5)
+
+@test()
+def test_map_shifted(ctx):
+    parser = MapTransform(JustTransform("arbre"), lambda a: (9, a))
+    input = "..arbre....."
+    assert parser.parse(input, 2) == Success((9, "arbre"), 7)
+
+@test()
+def test_map_failure(ctx):
+    parser = MapTransform(JustTransform("arbre"), lambda a: (9, a))
+    input = "......"
+    assert parser.parse(input, 2) == Failure(2, set(["arbre"]))
diff --git a/src/pyalibert/transformers/option.py b/src/pyalibert/transformers/option.py
index 679fced..6652bf1 100644
--- a/src/pyalibert/transformers/option.py
+++ b/src/pyalibert/transformers/option.py
@@ -8,11 +8,39 @@ from ..transformer import Transformer
 T = TypeVar("T")
 @dataclass
 class OptionTransform(Transformer[Optional[T]]):
-    def __init__(self, value: Transformer[T]):
-        self.value = value
+    value: Transformer[T]
     
     def parse(self, stream: str, at_index: int) -> Result[Optional[T]]:
         result = self.value.parse(stream, at_index)
         if isinstance(result, Success):
             return Success(result.value, result.next_index)
         return Success(None, at_index)
+
+
+from okipy.lib import test
+from .just import JustTransform
+
+
+@test()
+def test_opt_simple(ctx):
+    parser = OptionTransform(JustTransform("arbre"))
+    input = "arbre"
+    assert parser.parse(input, 0) == Success("arbre", 5)
+
+@test()
+def test_opt_none(ctx):
+    parser = OptionTransform(JustTransform("arbre"))
+    input = "brear"
+    assert parser.parse(input, 0) == Success(None, 0)
+
+@test()
+def test_opt_shifted(ctx):
+    parser = OptionTransform(JustTransform("arbre"))
+    input = "..arbre..."
+    assert parser.parse(input, 2) == Success("arbre", 7)
+
+@test()
+def test_opt_none_shifted(ctx):
+    parser = OptionTransform(JustTransform("arbre"))
+    input = "..rbrea..."
+    assert parser.parse(input, 2) == Success(None, 2)
diff --git a/src/pyalibert/transformers/or_.py b/src/pyalibert/transformers/or_.py
index 91ec158..59254c0 100644
--- a/src/pyalibert/transformers/or_.py
+++ b/src/pyalibert/transformers/or_.py
@@ -9,9 +9,8 @@ L = TypeVar("L")
 R = TypeVar("R")
 @dataclass
 class OrTransform(Transformer[Union[L, R]]):
-    def __init__(self, left: Transformer[L], right: Transformer[R]):
-        self.left = left
-        self.right = right
+    left: Transformer[L]
+    right: Transformer[R]
 
     def parse(self, stream: str, at_index: int) -> Result[Union[L, R]]:
         result_left = self.left.parse(stream, at_index)
@@ -21,3 +20,32 @@ class OrTransform(Transformer[Union[L, R]]):
         if isinstance(result_right, Success):
             return Success(result_right.value, result_right.next_index)
         return Failure(at_index, result_left.expected.union(result_right.expected))
+
+
+from okipy.lib import test
+from .just import JustTransform
+
+
+@test()
+def test_or_simple(ctx):
+    parser = OrTransform(JustTransform("ar"), JustTransform("bre"))
+    input = "arbre"
+    assert parser.parse(input, 0) == Success("ar", 2)
+
+@test()
+def test_or_other(ctx):
+    parser = OrTransform(JustTransform("ar"), JustTransform("bre"))
+    input = "brear"
+    assert parser.parse(input, 0) == Success("bre", 3)
+
+@test()
+def test_or_shifted(ctx):
+    parser = OrTransform(JustTransform("ar"), JustTransform("bre"))
+    input = "..arbre..."
+    assert parser.parse(input, 2) == Success("ar", 4)
+
+@test()
+def test_or_fail(ctx):
+    parser = OrTransform(JustTransform("ar"), JustTransform("bre"))
+    input = "......"
+    assert parser.parse(input, 2) == Failure(2, set(["ar", "bre"]))
diff --git a/src/pyalibert/transformers/regex.py b/src/pyalibert/transformers/regex.py
index f55cbb2..a4952e5 100644
--- a/src/pyalibert/transformers/regex.py
+++ b/src/pyalibert/transformers/regex.py
@@ -7,13 +7,40 @@ from ..transformer import Transformer
 
 @dataclass
 class RegexTransform(Transformer[str]):
-    def __init__(self, pattern: str):
-        self.pattern = pattern
+    pattern: str
 
     def parse(self, stream: str, at_index: int) -> Result[str]:
         do_match = re.match(self.pattern, stream[at_index:])
         if do_match is None:
-            return Failure(at_index, set(f"<matching '{self.pattern}'>"))
+            return Failure(at_index, set([f"<matching '{self.pattern}'>"]))
         else:
             match = do_match[0]
             return Success(match, at_index + len(match))
+
+
+from okipy.lib import test
+
+
+@test()
+def test_regex_simple(ctx):
+    parser = RegexTransform("arbre")
+    input = "arbre"
+    assert parser.parse(input, 0) == Success("arbre", 5)
+
+@test()
+def test_regex_shifted(ctx):
+    parser = RegexTransform("arbre")
+    input = "..arbre..."
+    assert parser.parse(input, 2) == Success("arbre", 7)
+
+@test()
+def test_regex_fails(ctx):
+    parser = RegexTransform("arbre")
+    input = "arbre......"
+    assert parser.parse(input, 2) == Failure(2, set(["<matching 'arbre'>"]))
+
+@test()
+def test_regex_some(ctx):
+    parser = RegexTransform("[0-3]+")
+    input = "012345"
+    assert parser.parse(input, 0) == Success("0123", 4)
diff --git a/src/pyalibert/transformers/sep_list.py b/src/pyalibert/transformers/sep_list.py
index 4c1619a..47e9421 100644
--- a/src/pyalibert/transformers/sep_list.py
+++ b/src/pyalibert/transformers/sep_list.py
@@ -1,5 +1,5 @@
 from dataclasses import dataclass
-from typing import Optional, TypeVar
+from typing import Generic, Optional, TypeVar
 
 from ..result import Result
 from ..transformer import Transformer
@@ -13,7 +13,10 @@ from .list import ListTransform
 T = TypeVar("T")
 S = TypeVar("S")
 @dataclass
-class SepListTransform(Transformer[list[T]]):
+class SepListTransform(Generic[T, S], Transformer[list[T]]):
+    items: Transformer[T]
+    sep: Transformer[S]
+
     def __init__(self, items: Transformer[T], sep: Transformer[S]):
         self.items = items
         self.sep = sep
@@ -33,3 +36,33 @@ class SepListTransform(Transformer[list[T]]):
         for (_sep, item) in value[1]:
             items.append(item)
         return items
+
+
+from okipy.lib import test
+from .just import JustTransform
+from ..result import Result, Success, Failure
+
+
+@test()
+def test_sep_simple(ctx):
+    parser = SepListTransform(JustTransform("arbre"), JustTransform(","))
+    input = "arbre"
+    assert parser.parse(input, 0) == Success(["arbre"], 5)
+
+@test()
+def test_sep_alt(ctx):
+    parser = SepListTransform(JustTransform("arbre"), JustTransform(","))
+    input = "arbre,arbre"
+    assert parser.parse(input, 0) == Success(["arbre", "arbre"], 11)
+
+@test()
+def test_sep_none(ctx):
+    parser = SepListTransform(JustTransform("arbre"), JustTransform(","))
+    input = ""
+    assert parser.parse(input, 2) == Success([], 2)
+
+@test()
+def test_sep_missing_not_failure(ctx):
+    parser = SepListTransform(JustTransform("arbre"), JustTransform(","))
+    input = "arbre,"
+    assert parser.parse(input, 0) == Success(['arbre'], 5)
diff --git a/src/pyalibert/transformers/value.py b/src/pyalibert/transformers/value.py
index 724e88b..4a90099 100644
--- a/src/pyalibert/transformers/value.py
+++ b/src/pyalibert/transformers/value.py
@@ -11,8 +11,29 @@ I = TypeVar("I")
 T = TypeVar("T")
 @dataclass
 class ValueTransform(Transformer[T]):
+    value: T
+
     def __init__(self, ignored: Transformer[I], value: T):
+        self.value = value
         self.actual = MapTransform(ignored, lambda _: value)
 
     def parse(self, stream: str, at_index: int) -> Result[T]:
         return self.actual.parse(stream, at_index)
+
+
+from okipy.lib import test
+from .just import JustTransform
+from ..result import Result, Success, Failure
+
+
+@test()
+def test_value_simple(ctx):
+    parser = ValueTransform(JustTransform("arbre"), "Feur")
+    input = "arbre"
+    assert parser.parse(input, 0) == Success("Feur", 5)
+
+@test()
+def test_value_failure(ctx):
+    parser = ValueTransform(JustTransform("arbre"), lambda a: (9, a))
+    input = "......"
+    assert parser.parse(input, 2) == Failure(2, set(["arbre"]))