diff --git a/CHANGELOG.md b/CHANGELOG.md
index d41c572cc..d9d6b451a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Celery task `FailableTask` that contains the logic to store the failure report, that can be re-used in different assets. ([#727](https://github.com/Substra/substra-backend/pull/727))
 - Add `FunctionStatus` enum ([#714](https://github.com/Substra/orchestrator/pull/714))
 - BREAKING: Add `status` on `api.Function` (type `FunctionStatus`) ([#714](https://github.com/Substra/substra-backend/pull/714))
+- Tests to ensure build order is made in order of submission (including retries) ([#740](https://github.com/Substra/substra-backend/pull/740))
 
 ### Changed
 
diff --git a/backend/backend/settings/test.py b/backend/backend/settings/test.py
index 29d3905a8..166f76f10 100644
--- a/backend/backend/settings/test.py
+++ b/backend/backend/settings/test.py
@@ -31,3 +31,7 @@
 
 MSP_ID = "testOrgMSP"
 CHANNELS = {"mychannel": {"model_export_enabled": False}}
+
+CELERY_BROKER_URL = "memory://"
+CELERY_RESULT_BACKEND = "cache+memory://"
+CELERY_TASK_ALWAYS_EAGER = False
diff --git a/backend/builder/tasks/task.py b/backend/builder/tasks/task.py
index 459f00e99..50f59ddb3 100644
--- a/backend/builder/tasks/task.py
+++ b/backend/builder/tasks/task.py
@@ -34,6 +34,6 @@ def before_start(self, task_id: str, args: tuple, kwargs: dict) -> None:
             )
 
     def get_task_info(self, args: tuple, kwargs: dict) -> tuple[str, str]:
-        function = orchestrator.Function.parse_raw(kwargs["function_serialized"])
+        function = orchestrator.Function.model_validate_json(kwargs["function_serialized"])
         channel_name = kwargs["channel_name"]
         return function.key, channel_name
diff --git a/backend/builder/tasks/tasks_build_image.py b/backend/builder/tasks/tasks_build_image.py
index dda71d8dc..d335fe1c4 100644
--- a/backend/builder/tasks/tasks_build_image.py
+++ b/backend/builder/tasks/tasks_build_image.py
@@ -20,7 +20,7 @@
 # see http://docs.celeryproject.org/en/latest/userguide/configuration.html#task-reject-on-worker-lost
 # and https://github.com/celery/celery/issues/5106
 def build_image(task: BuildTask, function_serialized: str, channel_name: str) -> None:
-    function = orchestrator.Function.parse_raw(function_serialized)
+    function = orchestrator.Function.model_validate_json(function_serialized)
 
     attempt = 0
     while attempt <= task.max_retries:
diff --git a/backend/builder/tests/test_task_build_image.py b/backend/builder/tests/test_task_build_image.py
index 151821d57..bb868d196 100644
--- a/backend/builder/tests/test_task_build_image.py
+++ b/backend/builder/tests/test_task_build_image.py
@@ -1,9 +1,17 @@
+import time
+
+import celery
 import pytest
 
+import orchestrator.mock as orc_mock
 from builder.exceptions import BuildError
+from builder.exceptions import BuildRetryError
+from builder.tasks.tasks_build_image import build_image
 from substrapp.models import FailedAssetKind
 from substrapp.utils.errors import store_failure
 
+CHANNEL = "mychannel"
+
 
 @pytest.mark.django_db
 def test_store_failure_build_error():
@@ -18,3 +26,60 @@ def test_store_failure_build_error():
 
     assert str(failure_report.asset_key) == compute_task_key
     assert failure_report.logs.read() == str.encode(msg)
+
+
+@pytest.mark.parametrize("execution_number", range(10))
+def test_order_building_success(celery_app, celery_worker, mocker, execution_number):
+    function_1 = orc_mock.FunctionFactory()
+    function_2 = orc_mock.FunctionFactory()
+
+    # BuildTask `before_start` uses this client to change the status, which would lead to `OrcError`
+    mocker.patch("builder.tasks.task.get_orchestrator_client")
+    mocker.patch("builder.tasks.tasks_build_image.build_image_if_missing", side_effect=lambda x, y: time.sleep(0.5))
+
+    result_1 = build_image.apply_async(
+        kwargs={"function_serialized": function_1.model_dump_json(), "channel_name": CHANNEL}
+    )
+    result_2 = build_image.apply_async(
+        kwargs={"function_serialized": function_2.model_dump_json(), "channel_name": CHANNEL}
+    )
+    # get waits for the completion
+    result_1.get()
+
+    assert result_1.state == celery.states.SUCCESS
+    assert result_2.state == "WAITING"
+
+
+@pytest.mark.parametrize("execution_number", range(10))
+def test_order_building_retry(celery_app, celery_worker, mocker, execution_number):
+    function_retry = orc_mock.FunctionFactory()
+    function_other = orc_mock.FunctionFactory()
+
+    # Only retry once for function_retry
+    def side_effect_creator():
+        already_raised = False
+
+        def side_effect(*args, **kwargs):
+            nonlocal already_raised
+            time.sleep(0.5)
+            key = args[1].key
+            if not already_raised and function_retry.key == key:
+                already_raised = True
+                raise BuildRetryError("random retriable error")
+
+        return side_effect
+
+    # BuildTask `before_start` uses this client to change the status, which would lead to `OrcError`
+    mocker.patch("builder.tasks.task.get_orchestrator_client")
+    mocker.patch("builder.tasks.tasks_build_image.build_image_if_missing", side_effect=side_effect_creator())
+
+    result_retry = build_image.apply_async(
+        kwargs={"function_serialized": function_retry.model_dump_json(), "channel_name": CHANNEL}
+    )
+    result_other = build_image.apply_async(
+        kwargs={"function_serialized": function_other.model_dump_json(), "channel_name": CHANNEL}
+    )
+
+    result_retry.get()
+    assert result_retry.state == celery.states.SUCCESS
+    assert result_other.state == "WAITING"
diff --git a/backend/dev-requirements.txt b/backend/dev-requirements.txt
index eac575e7a..877c2e474 100644
--- a/backend/dev-requirements.txt
+++ b/backend/dev-requirements.txt
@@ -21,4 +21,5 @@ mypy==1.4.1
 djangorestframework-stubs==1.8.0
 django-stubs==1.14.0
 celery-types==0.14.0
-docker==6.1.3
\ No newline at end of file
+docker==6.1.3
+celery[pytest]
\ No newline at end of file
diff --git a/backend/substrapp/tasks/task.py b/backend/substrapp/tasks/task.py
index 9c1915192..60db3d507 100644
--- a/backend/substrapp/tasks/task.py
+++ b/backend/substrapp/tasks/task.py
@@ -91,7 +91,7 @@ def on_retry(self, exc: Exception, task_id: str, args: tuple, kwargs: dict[str,
 
     def split_args(self, celery_args: tuple) -> tuple[str, orchestrator.ComputeTask]:
         channel_name = celery_args[0]
-        task = orchestrator.ComputeTask.parse_raw(celery_args[1])
+        task = orchestrator.ComputeTask.model_validate_json(celery_args[1])
         return channel_name, task
 
     def get_task_info(self, args: tuple, kwargs: dict) -> tuple[str, str]:
diff --git a/backend/substrapp/tasks/tasks_save_image.py b/backend/substrapp/tasks/tasks_save_image.py
index 1ada2b6ae..15d9eaf16 100644
--- a/backend/substrapp/tasks/tasks_save_image.py
+++ b/backend/substrapp/tasks/tasks_save_image.py
@@ -46,7 +46,7 @@ def attempt(self) -> int:
 
     # Returns (function key, channel)
     def get_task_info(self, args: tuple, kwargs: dict) -> tuple[str, str]:
-        function = orchestrator.Function.parse_raw(kwargs["function_serialized"])
+        function = orchestrator.Function.model_validate_json(kwargs["function_serialized"])
         channel_name = kwargs["channel_name"]
         return function.key, channel_name
 
@@ -75,7 +75,7 @@ def save_image_task(task: SaveImageTask, function_serialized: str, channel_name:
     logger.info("Starting save_image_task")
     logger.info(f"Parameters: function_serialized {function_serialized}, " f"channel_name {channel_name}")
     # create serialized image
-    function = orchestrator.Function.parse_raw(function_serialized)
+    function = orchestrator.Function.model_validate_json(function_serialized)
     container_image_tag = utils.container_image_tag_from_function(function)
 
     os.makedirs(SUBTUPLE_TMP_DIR, exist_ok=True)