diff --git a/.gitignore b/.gitignore
index 3910ba5..f140124 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 # specific on the project
 *credential.py
+/roulier/tests/credentials.py
 *label*.pdf  # files downloaded when executed some tests
 
 # Byte-compiled / optimized / DLL files
diff --git a/roulier/tests/__init__.py b/roulier/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/roulier/tests/conftest.py b/roulier/tests/conftest.py
new file mode 100644
index 0000000..dfe72c0
--- /dev/null
+++ b/roulier/tests/conftest.py
@@ -0,0 +1,58 @@
+# Copyright 2024 Akretion (http://www.akretion.com).
+# @author Florian Mounier <florian.mounier@akretion.com>
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+from datetime import date
+import pytest
+
+try:
+    from .credentials import CREDENTIALS
+except ImportError:
+    from .credentials_demo import CREDENTIALS
+
+
+@pytest.fixture(scope="session")
+def credentials():
+    return {
+        **CREDENTIALS,
+        "isTest": True,
+    }
+
+
+@pytest.fixture
+def base_get_label_data():
+    return {
+        "service": {
+            "shippingDate": date(2024, 1, 1),
+            "labelFormat": "PDF",
+        },
+        "parcels": [{"weight": 1.2, "comment": "Fake comment"}],
+        "from_address": {
+            "name": "Akrétion",
+            "street1": "27 rue Henri Rolland",
+            "street2": "Batiment B",
+            "city": "Villeurbanne",
+            "zip": "69100",
+            "country": "FR",
+            "phone": "+33482538457",
+        },
+        "to_address": {
+            "name": "Hügǒ",
+            "firstName": "Victor",
+            "street1": "6 Place des Vôsges",
+            "city": "Paris",
+            "zip": "75004",
+            "country": "FR",
+            "email": "hugo.victor@example.com",
+            "phone": "+33600000000",
+        },
+    }
+
+
+@pytest.fixture
+def base_find_pickup_site_data():
+    return {
+        "search": {
+            "country": "FR",
+            "zip": "69100",
+        },
+    }
diff --git a/roulier/tests/credentials_demo.py b/roulier/tests/credentials_demo.py
new file mode 100644
index 0000000..4f5dabd
--- /dev/null
+++ b/roulier/tests/credentials_demo.py
@@ -0,0 +1,12 @@
+# Copyright 2024 Akretion (http://www.akretion.com).
+# @author Florian Mounier <florian.mounier@akretion.com>
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+"""Copy this file to credentials.py and fill in your test credentials"""
+
+CREDENTIALS = {
+    "mondialrelay_fr": {  # These are public test credentials
+        "login": "BDTEST13",
+        "password": "PrivateK",
+    },
+}
diff --git a/roulier/tests/test_api.py b/roulier/tests/test_api.py
new file mode 100644
index 0000000..df2b89f
--- /dev/null
+++ b/roulier/tests/test_api.py
@@ -0,0 +1,272 @@
+# Copyright 2024 Akretion (http://www.akretion.com).
+# @author Florian Mounier <florian.mounier@akretion.com>
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+from roulier import roulier
+from roulier.carrier import Carrier, action
+from roulier.exception import CarrierError, InvalidApiInput
+from pydantic import BaseModel
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def reset_roulier():
+    roulier.factory._carrier_action = {}
+
+
+def test_carrier_api():
+    assert "dummy" not in roulier.get_carriers_action_available()
+
+    class DummyIn(BaseModel):
+        name: str
+        id: int
+
+    class DummyOut(BaseModel):
+        outname: str
+        outid: int
+
+        @classmethod
+        def from_in(cls, data: DummyIn):
+            return cls(outname=data.name, outid=data.id)
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        @action
+        def get(self, input: DummyIn) -> DummyOut:
+            assert input.name == "test"
+            assert input.id == 1
+
+            return DummyOut.from_in(input)
+
+    assert "dummy" in roulier.get_carriers_action_available()
+    assert roulier.get_carriers_action_available()["dummy"] == ["get"]
+
+    rv = roulier.get("dummy", "get", {"name": "test", "id": 1})
+    assert rv == {"outname": "test", "outid": 1}
+
+
+def test_carrier_api_unexposed():
+    class DummySubIn(BaseModel):
+        key: str
+
+    class DummyIn(BaseModel):
+        name: str | None = None
+        subs: list[DummySubIn]
+
+    class DummyOut(BaseModel):
+        len: int
+
+        @classmethod
+        def from_in(cls, data: DummyIn):
+            return cls(len=len(data.subs))
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        def unexposed(self, input: DummyIn) -> DummyOut:
+            """This should not be exposed."""
+
+        @action
+        def acquire(self, input: DummyIn) -> DummyOut:
+            assert input.name == None
+            assert len(input.subs) == 2
+            return DummyOut.from_in(input)
+
+    assert "dummy" in roulier.get_carriers_action_available()
+    assert roulier.get_carriers_action_available()["dummy"] == ["acquire"]
+
+    rv = roulier.get("dummy", "acquire", {"subs": [{"key": "test"}, {"key": "test2"}]})
+    assert rv == {"len": 2}
+
+
+def test_carrier_api_bad_input_signature():
+
+    class DummyOut(BaseModel):
+        pass
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        @action
+        def get(self, input) -> DummyOut:
+            pass
+
+    with pytest.raises(ValueError) as excinfo:
+        roulier.get("dummy", "get", {})
+    assert "Missing input argument or type hint" in str(excinfo.value)
+
+
+def test_carrier_api_bad_output_signature():
+    class DummyIn(BaseModel):
+        pass
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        @action
+        def get(self, input: DummyIn):
+            pass
+
+    with pytest.raises(ValueError) as excinfo:
+        roulier.get("dummy", "get", {})
+    assert "Missing return type hint" in str(excinfo.value)
+
+
+def test_carrier_api_invalid_input():
+    class DummyIn(BaseModel):
+        name: str
+        id: int
+
+    class DummyOut(BaseModel):
+        outname: str
+        outid: int
+
+        @classmethod
+        def from_in(cls, data: DummyIn):
+            return cls(outname=data.name, outid=data.id)
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        @action
+        def get(self, input: DummyIn) -> DummyOut:
+            return DummyOut.from_in(input)
+
+    assert "dummy" in roulier.get_carriers_action_available()
+    assert roulier.get_carriers_action_available()["dummy"] == ["get"]
+
+    with pytest.raises(InvalidApiInput) as excinfo:
+        roulier.get("dummy", "get", {"description": "test", "id": 1})
+
+    assert "Invalid input data" in str(excinfo.value)
+    assert "name\n  Field required" in str(excinfo.value)
+
+
+def test_carrier_api_invalid_output():
+    class DummyIn(BaseModel):
+        name: str
+        id: int
+
+    class DummyOut(BaseModel):
+        outname: str
+        outid: int
+
+        @classmethod
+        def from_in(cls, data: DummyIn):
+            return cls(out=data.name)
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        @action
+        def get(self, input: DummyIn) -> DummyOut:
+            return DummyOut.from_in(input)
+
+    assert "dummy" in roulier.get_carriers_action_available()
+    assert roulier.get_carriers_action_available()["dummy"] == ["get"]
+
+    with pytest.raises(CarrierError) as excinfo:
+        roulier.get("dummy", "get", {"name": "test", "id": 1})
+
+    assert "Action failed" in str(excinfo.value)
+    assert "outname\n  Field required" in str(excinfo.value)
+
+
+def test_carrier_api_carrier_error():
+    class DummyIn(BaseModel):
+        name: str
+        id: int
+
+    class DummyOut(BaseModel):
+        outname: str
+        outid: int
+
+        @classmethod
+        def from_in(cls, data: DummyIn):
+            return cls(outname=data.name, outid=data.id)
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        @action
+        def get(self, input: DummyIn) -> DummyOut:
+            raise CarrierError({"url": "http://fail"}, "This failed miserably")
+
+    assert "dummy" in roulier.get_carriers_action_available()
+    assert roulier.get_carriers_action_available()["dummy"] == ["get"]
+
+    with pytest.raises(CarrierError) as excinfo:
+        roulier.get("dummy", "get", {"name": "test", "id": 1})
+
+    assert "This failed miserably" in str(excinfo.value)
+    assert excinfo.value.response == {"url": "http://fail"}
+
+
+def test_carrier_api_extra_input():
+    class DummyIn(BaseModel):
+        name: str
+        id: int
+
+    class DummyOut(BaseModel):
+        outname: str
+        outid: int
+
+        @classmethod
+        def from_in(cls, data: DummyIn):
+            return cls(outname=data.name, outid=data.id)
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        @action
+        def get(self, input: DummyIn) -> DummyOut:
+            return DummyOut.from_in(input)
+
+    assert "dummy" in roulier.get_carriers_action_available()
+    assert roulier.get_carriers_action_available()["dummy"] == ["get"]
+
+    rv = roulier.get("dummy", "get", {"name": "test", "description": "test", "id": 1})
+    assert rv == {"outname": "test", "outid": 1}
+
+
+def test_carrier_api_multi_actions():
+    class DummyIn(BaseModel):
+        name: str
+        id: int
+
+    class DummyOut(BaseModel):
+        outname: str
+        outid: int
+
+        @classmethod
+        def from_in(cls, data: DummyIn):
+            return cls(outname=data.name, outid=data.id)
+
+    class DummyAcquireOut(BaseModel):
+        out: str
+
+        @classmethod
+        def from_in(cls, data: DummyIn):
+            return cls(out=f"[{data.id}] {data.name}")
+
+    class DummyCarrier(Carrier):
+        __key__ = "dummy"
+
+        @action
+        def get(self, input: DummyIn) -> DummyOut:
+            return DummyOut.from_in(input)
+
+        @action
+        def acquire(self, input: DummyIn) -> DummyAcquireOut:
+            return DummyAcquireOut.from_in(input)
+
+    assert "dummy" in roulier.get_carriers_action_available()
+    assert roulier.get_carriers_action_available()["dummy"] == ["get", "acquire"]
+
+    rv = roulier.get("dummy", "get", {"name": "test", "description": "test", "id": 1})
+    assert rv == {"outname": "test", "outid": 1}
+
+    rv = roulier.get(
+        "dummy", "acquire", {"name": "test", "description": "test", "id": 1}
+    )
+    assert rv == {"out": "[1] test"}
diff --git a/roulier/tests/test_helpers.py b/roulier/tests/test_helpers.py
new file mode 100644
index 0000000..b2eff52
--- /dev/null
+++ b/roulier/tests/test_helpers.py
@@ -0,0 +1,129 @@
+# Copyright 2024 Akretion (http://www.akretion.com).
+# @author Florian Mounier <florian.mounier@akretion.com>
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+from ..helpers import (
+    filter_empty,
+    merge,
+    none_as_empty,
+    prefix,
+    suffix,
+    unaccent,
+    walk_data,
+)
+
+
+def test_prefix():
+    assert prefix({"a": 1, "b": 2}, "p_") == {"p_a": 1, "p_b": 2}
+
+
+def test_suffix():
+    assert suffix({"a": 1, "b": 2}, "_s") == {"a_s": 1, "b_s": 2}
+
+
+def test_walk_data():
+    assert walk_data(
+        {
+            "a": 1,
+            "b": {
+                "c": 3,
+                "d": {"a": 5, "f": 6},
+            },
+        }
+    ) == {
+        "a": 1,
+        "b": {
+            "c": 3,
+            "d": {"a": 5, "f": 6},
+        },
+    }
+    assert walk_data(
+        {
+            "a": 1,
+            "b": {
+                "c": 3,
+                "d": {"a": 5, "f": 6},
+            },
+        },
+        filter=lambda x: x not in [1, 5],
+    ) == {"b": {"c": 3, "d": {"f": 6}}}
+    assert walk_data(
+        {
+            "a": 1,
+            "b": {
+                "c": 3,
+                "d": {"a": 5, "f": 6},
+            },
+        },
+        transform=lambda x: x + 1,
+    ) == {
+        "a": 2,
+        "b": {
+            "c": 4,
+            "d": {"a": 6, "f": 7},
+        },
+    }
+
+
+def test_filter_empty():
+    assert filter_empty(
+        {
+            "a": 1,
+            "b": None,
+            "c": "",
+        }
+    ) == {"a": 1}
+    assert filter_empty(
+        {
+            "a": 1,
+            "b": {"c": None, "d": {"a": 5, "f": ""}},
+        }
+    ) == {
+        "a": 1,
+        "b": {"d": {"a": 5}},
+    }
+
+
+def test_none_as_empty():
+    assert none_as_empty({"a": 1, "b": None}) == {"a": 1, "b": ""}
+
+
+def test_unaccent():
+    assert unaccent("éà") == "ea"
+    assert unaccent({"a": "éà", "b": {"c": 12, "d": ["çô", "ë"]}}) == {
+        "a": "ea",
+        "b": {"c": 12, "d": ["co", "e"]},
+    }
+
+
+def test_merge():
+    assert merge({"a": 1}, {"b": 2}) == {"a": 1, "b": 2}
+    assert merge({"a": 1}, {"a": None}) == {"a": 1}
+    assert merge({"a": 1}, {"a": ""}) == {"a": 1}
+    assert merge({"a": None}, {"a": 1}) == {"a": 1}
+    assert merge({"a": ""}, {"a": 1}) == {"a": 1}
+    assert merge({"a": 1}, {"a": 2}, {"a": 3}) == {"a": 3}
+    assert merge(
+        {
+            "a": {"b": 1},
+        },
+        {
+            "a": {"c": 2},
+        },
+    ) == {
+        "a": {"b": 1, "c": 2},
+    }
+    assert merge({"a": {"b": 1}}, {"a": {"b": 2}}) == {"a": {"b": 2}}
+    assert merge({"a": {"b": 1}}, {"a": {"b": 2}}, {"a": {"b": 3}}) == {"a": {"b": 3}}
+    assert merge({"a": {"b": 1}}, {"a": {"b": 2}}, {"a": {"b": None}}) == {
+        "a": {"b": 2}
+    }
+    assert merge({"a": {"b": 1}}, {"a": {"b": 2}}, {"a": {"b": ""}}) == {"a": {"b": 2}}
+    assert merge({"a": {"b": 1}}, {"a": {"b": None}}, {"a": {"b": 3}}) == {
+        "a": {"b": 3}
+    }
+    assert merge({"a": {"b": 1}}, {"a": {"b": ""}}, {"a": {"b": 3}}) == {"a": {"b": 3}}
+    assert merge(
+        {"a": {"b": 1}}, {"a": {"b": 2}}, {"a": {"b": 3}}, {"a": {"b": None}}
+    ) == {"a": {"b": 3}}
+    assert merge({"a": {"b": 1}}, {"a": {"b": 2}}, {"a": {"b": 3}}, {"a": {"b": ""}})
diff --git a/setup.py b/setup.py
index 9083957..1160ad3 100755
--- a/setup.py
+++ b/setup.py
@@ -24,7 +24,7 @@
         "zeep",
     ],
     extras_requires={
-        "dev": ["ptpython", "pytest"],
+        "dev": ["pytest", "pytest-recording"],
     },
     author="Hparfr <https://github.com/hparfr>",
     author_email="roulier@hpar.fr",