diff --git a/aircox/models/diffusion.py b/aircox/models/diffusion.py
index 972d0dc..2949885 100644
--- a/aircox/models/diffusion.py
+++ b/aircox/models/diffusion.py
@@ -165,7 +165,7 @@ class Diffusion(Rerun):
 
     def save_rerun(self):
         self.episode = self.initial.episode
-        self.program = self.episode.program
+        super().save_rerun()
 
     def save_initial(self):
         self.program = self.episode.program
diff --git a/aircox/models/rerun.py b/aircox/models/rerun.py
index a6dd9a2..59b7c20 100644
--- a/aircox/models/rerun.py
+++ b/aircox/models/rerun.py
@@ -64,24 +64,6 @@ class Rerun(models.Model):
     class Meta:
         abstract = True
 
-    def save(self, *args, **kwargs):
-        if self.initial is not None:
-            self.initial = self.initial.get_initial()
-        if self.initial == self:
-            self.initial = None
-
-        if self.is_rerun:
-            self.save_rerun()
-        else:
-            self.save_initial()
-        super().save(*args, **kwargs)
-
-    def save_rerun(self):
-        pass
-
-    def save_initial(self):
-        pass
-
     @property
     def is_initial(self):
         return self.initial is None
@@ -96,7 +78,29 @@ class Rerun(models.Model):
 
     def clean(self):
         super().clean()
-        if self.initial is not None and self.initial.start >= self.start:
+        if (
+            hasattr(self, "start")
+            and self.initial is not None
+            and self.initial.start >= self.start
+        ):
             raise ValidationError(
                 {"initial": _("rerun must happen after original")}
             )
+
+    def save_rerun(self):
+        self.program = self.initial.program
+
+    def save_initial(self):
+        pass
+
+    def save(self, *args, **kwargs):
+        if self.initial is not None:
+            self.initial = self.initial.get_initial()
+        if self.initial == self:
+            self.initial = None
+
+        if self.is_rerun:
+            self.save_rerun()
+        else:
+            self.save_initial()
+        super().save(*args, **kwargs)
diff --git a/aircox/models/schedule.py b/aircox/models/schedule.py
index b350ac8..ef1388d 100644
--- a/aircox/models/schedule.py
+++ b/aircox/models/schedule.py
@@ -75,8 +75,8 @@ class Schedule(Rerun):
             self.time.strftime("%H:%M"),
         )
 
-    def save_rerun(self, *args, **kwargs):
-        self.program = self.initial.program
+    def save_rerun(self):
+        super().save_rerun()
         self.duration = self.initial.duration
         self.frequency = self.initial.frequency
 
@@ -107,23 +107,6 @@ class Schedule(Rerun):
             .capitalize()
         )
 
-    # initial cached data
-    __initial = None
-
-    def changed(self, fields=["date", "duration", "frequency", "timezone"]):
-        initial = self._Schedule__initial
-
-        if not initial:
-            return
-
-        this = self.__dict__
-
-        for field in fields:
-            if initial.get(field) != this.get(field):
-                return True
-
-        return False
-
     def normalize(self, date):
         """Return a datetime set to schedule's time for the provided date,
         handling timezone (based on schedule's timezone)."""
@@ -245,10 +228,3 @@ class Schedule(Rerun):
                 end=date + duration,
             )
         return episodes.values(), diffusions.values()
-
-    def __init__(self, *args, **kwargs):
-        super().__init__(*args, **kwargs)
-
-        # TODO/FIXME: use validators?
-        if self.initial is not None and self.date > self.date:
-            raise ValueError("initial must be later")
diff --git a/aircox/tests/conftest.py b/aircox/tests/conftest.py
new file mode 100644
index 0000000..ed26e75
--- /dev/null
+++ b/aircox/tests/conftest.py
@@ -0,0 +1,63 @@
+from datetime import time, timedelta
+import itertools
+
+import pytest
+from model_bakery import baker
+
+from aircox.models import Diffusion
+
+
+@pytest.fixture
+def stations():
+    return baker.make("aircox.station", quantity=2)
+
+
+@pytest.fixture
+def programs(stations):
+    return list(
+        itertools.chain(
+            *(
+                baker.make("aircox.program", quantity=3, station=station)
+                for station in stations
+            )
+        )
+    )
+
+
+@pytest.fixture
+def sched_initials(programs):
+    # use concrete class
+    return [
+        baker.make("aircox.schedule", program=program, time=time(16, 00))
+        for program in programs
+    ]
+
+
+@pytest.fixture
+def sched_reruns(initials):
+    # use concrete class
+    return [
+        baker.make(
+            "aircox.schedule",
+            initial=initial,
+            date=initial.date,
+            time=(initial.start + timedelta(hours=1)).time(),
+        )
+        for initial in initials
+    ]
+
+
+@pytest.fixture
+def schedules(sched_initials, sched_reruns):
+    return sched_initials + sched_reruns
+
+
+@pytest.fixture
+def episodes(programs):
+    items = []
+    for program in programs:
+        items += [
+            baker.make("aircox.episode", parent=program, type=type)
+            for type, _ in Diffusion.TYPE_CHOICES
+        ]
+    return items
diff --git a/aircox/tests/models/test_diffusion.py b/aircox/tests/models/test_diffusion.py
new file mode 100644
index 0000000..26b177b
--- /dev/null
+++ b/aircox/tests/models/test_diffusion.py
@@ -0,0 +1,19 @@
+import pytest
+
+
+class TestDiffusionQuerySet:
+    @pytest.mark.django_db
+    def test_episode_by_obj(self, episodes):
+        pass
+
+    @pytest.mark.django_db
+    def test_episode_by_id(self, episodes):
+        pass
+
+    @pytest.mark.django_db
+    def test_on_air(self, episodes):
+        pass
+
+    @pytest.mark.django_db
+    def test_now(self, episodes):
+        pass
diff --git a/aircox/tests/models/test_rerun.py b/aircox/tests/models/test_rerun.py
new file mode 100644
index 0000000..7f6529e
--- /dev/null
+++ b/aircox/tests/models/test_rerun.py
@@ -0,0 +1,117 @@
+from datetime import timedelta
+
+import pytest
+
+from django.core.exceptions import ValidationError
+
+# we use Schedule as concrete class (Rerun is abstract)
+from aircox.models import Schedule
+
+
+class TestRerunQuerySet:
+    @pytest.mark.django_db
+    def test_station_by_obj(self, stations):
+        for station in stations:
+            queryset = (
+                Schedule.objects.station(station)
+                .distinct()
+                .value_list("station", flat=True)
+            )
+            assert queryset.count() == 1
+            assert queryset.first() == station
+
+    @pytest.mark.django_db
+    def test_station_by_id(self, stations):
+        for station in stations:
+            queryset = (
+                Schedule.objects.station(id=station.pk)
+                .distinct()
+                .value_list("station", flat=True)
+            )
+            assert queryset.count() == 1
+            assert queryset.first() == station
+
+    @pytest.mark.django_db
+    def test_program_by_obj(self, programs):
+        for program in programs:
+            queryset = (
+                Schedule.objects.program(program)
+                .distinct()
+                .value_list("program", flat=True)
+            )
+            assert queryset.count() == 1
+            assert queryset.first() == program
+
+    @pytest.mark.django_db
+    def test_program_by_id(self, programs):
+        for program in programs:
+            queryset = (
+                Schedule.objects.program(id=program.pk)
+                .distinct()
+                .value_list("program", flat=True)
+            )
+            assert queryset.count() == 1
+            assert queryset.first() == program
+
+    @pytest.mark.django_db
+    def test_rerun(self, sched_reruns):
+        queryset = Schedule.objects.rerun().value_list("initial", flat=True)
+        assert None not in queryset
+
+    @pytest.mark.django_db
+    def test_initial(self, sched_initials):
+        queryset = (
+            Schedule.objects.rerun()
+            .distinct()
+            .value_list("initial", flat=True)
+        )
+        assert queryset.count() == 1
+        assert queryset.first() is None
+
+
+class TestRerun:
+    @pytest.mark.django_db
+    def test_is_initial_true(self, sched_initials):
+        assert all(r.is_initial for r in sched_initials)
+
+    @pytest.mark.django_db
+    def test_is_initial_false(self, sched_reruns):
+        assert all(not r.is_initial for r in sched_reruns)
+
+    @pytest.mark.django_db
+    def test_is_rerun_true(self, sched_reruns):
+        assert all(r.is_rerun for r in sched_reruns)
+
+    @pytest.mark.django_db
+    def test_is_rerun_false(self, sched_initials):
+        assert all(not r.is_rerun for r in sched_initials)
+
+    @pytest.mark.django_db
+    def test_get_initial_of_initials(self, sched_initials):
+        assert all(r.get_initial() is r for r in sched_initials)
+
+    @pytest.mark.django_db
+    def test_get_initial_of_reruns(self, sched_reruns):
+        assert all(r.get_initial() is r.initial for r in sched_reruns)
+
+    @pytest.mark.django_db
+    def test_clean_success(self, sched_reruns):
+        for rerun in sched_reruns:
+            rerun.clean()
+
+    @pytest.mark.django_db
+    def test_clean_fails(self, sched_reruns):
+        for rerun in sched_reruns:
+            rerun.time = (rerun.initial.start - timedelta(hours=2)).time()
+            with pytest.raises(ValidationError):
+                rerun.clean()
+
+    @pytest.mark.django_db
+    def test_save_rerun(self, sched_reruns):
+        for rerun in sched_reruns:
+            rerun.program = None
+            rerun.save_rerun()
+            assert rerun.program == rerun.initial.program
+
+    # TODO: save()
+    # save_initial is empty, thus not tested
diff --git a/aircox/tests/models/test_schedule.py b/aircox/tests/models/test_schedule.py
new file mode 100644
index 0000000..bde431e
--- /dev/null
+++ b/aircox/tests/models/test_schedule.py
@@ -0,0 +1,74 @@
+import pytest
+from datetime import datetime
+
+from aircox import utils
+
+
+class TestSchedule:
+    @pytest.mark.django_db
+    def test_save_rerun(self, sched_reruns):
+        for schedule in sched_reruns:
+            schedule.duration = None
+            schedule.frequency = None
+            schedule.save_rerun()
+            assert schedule.program == schedule.initial.program
+            assert schedule.duration == schedule.initial.duration
+            assert schedule.frequency == schedule.initial.frequency
+
+    @pytest.mark.django_db
+    def test_tz(self, schedules):
+        for schedule in schedules:
+            assert schedule.timezone == schedule.tz.zone
+
+    @pytest.mark.django_db
+    def test_start(self, schedules):
+        for schedule in schedules:
+            assert schedule.start.date() == schedule.date
+            assert schedule.start.time() == schedule.time
+
+    @pytest.mark.django_db
+    def test_end(self, schedules):
+        for schedule in schedules:
+            delta = utils.to_timedelta(schedule.duration)
+            assert schedule.end - schedule.start == delta
+
+    # def test_get_frequency_verbose(self):
+    #    pass
+
+    @pytest.mark.django_db
+    def test_normalize(self, schedules):
+        for schedule in schedules:
+            dt = datetime.combine(schedule.date, schedule.time)
+            assert schedule.normalize(dt).tzinfo.zone == schedule.timezone.zone
+
+    @pytest.mark.django_db
+    def test_dates_of_month_ponctual(self):
+        pass
+
+    @pytest.mark.django_db
+    def test_dates_of_month_n_day_of_month(self):
+        pass
+
+    @pytest.mark.django_db
+    def test_dates_of_month_first_and_third(self):
+        pass
+
+    @pytest.mark.django_db
+    def test_dates_of_month_second_and_fourth(self):
+        pass
+
+    @pytest.mark.django_db
+    def test_dates_of_month_every(self):
+        pass
+
+    @pytest.mark.django_db
+    def test_dates_of_month_one_on_two(self):
+        pass
+
+    @pytest.mark.django_db
+    def test__exclude_existing_date(self):
+        pass
+
+    @pytest.mark.django_db
+    def test_diffusions_of_month(self):
+        pass
diff --git a/requirements_tests.txt b/requirements_tests.txt
index d18e0aa..9007f2b 100644
--- a/requirements_tests.txt
+++ b/requirements_tests.txt
@@ -1,2 +1,3 @@
 pytest~=7.2
 pytest-django~=4.5
+model_bakery~=1.10