diff --git a/tests/test_elements_worker/test_classifications.py b/tests/test_elements_worker/test_classifications.py
index 97531fe32260d090eb7b934013c1a47fc736cffa..047f9ae6e1d2915a2397c7b81db00efa56193b24 100644
--- a/tests/test_elements_worker/test_classifications.py
+++ b/tests/test_elements_worker/test_classifications.py
@@ -12,10 +12,10 @@ from . import BASE_API_CALLS
 
 
 def test_get_ml_class_id_load_classes(responses, mock_elements_worker):
-    corpus_id = mock_elements_worker.corpus_id
+    mock_elements_worker.corpus_id = "12341234-1234-1234-1234-123412341234"
     responses.add(
         responses.GET,
-        f"http://testserver/api/v1/corpus/{corpus_id}/classes/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/",
         status=200,
         json={
             "count": 1,
@@ -36,31 +36,31 @@ def test_get_ml_class_id_load_classes(responses, mock_elements_worker):
     assert [
         (call.request.method, call.request.url) for call in responses.calls
     ] == BASE_API_CALLS + [
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
     ]
     assert mock_elements_worker.classes == {
-        "11111111-1111-1111-1111-111111111111": {"good": "0000"}
+        "12341234-1234-1234-1234-123412341234": {"good": "0000"}
     }
     assert ml_class_id == "0000"
 
 
 def test_get_ml_class_id_inexistant_class(mock_elements_worker, responses):
     # A missing class is now created automatically
-    corpus_id = mock_elements_worker.corpus_id
+    mock_elements_worker.corpus_id  = "12341234-1234-1234-1234-123412341234"
     mock_elements_worker.classes = {
-        "11111111-1111-1111-1111-111111111111": {"good": "0000"}
+         "12341234-1234-1234-1234-123412341234": {"good": "0000"}
     }
 
     responses.add(
         responses.POST,
-        f"http://testserver/api/v1/corpus/{corpus_id}/classes/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/",
         status=201,
         json={"id": "new-ml-class-1234"},
     )
 
     # Missing class at first
     assert mock_elements_worker.classes == {
-        "11111111-1111-1111-1111-111111111111": {"good": "0000"}
+        "12341234-1234-1234-1234-123412341234": {"good": "0000"}
     }
 
     ml_class_id = mock_elements_worker.get_ml_class_id("bad")
@@ -68,7 +68,7 @@ def test_get_ml_class_id_inexistant_class(mock_elements_worker, responses):
 
     # Now it's available
     assert mock_elements_worker.classes == {
-        "11111111-1111-1111-1111-111111111111": {
+        "12341234-1234-1234-1234-123412341234": {
             "good": "0000",
             "bad": "new-ml-class-1234",
         }
@@ -76,9 +76,9 @@ def test_get_ml_class_id_inexistant_class(mock_elements_worker, responses):
 
 
 def test_get_ml_class_id(mock_elements_worker):
-    # corpus_id = "12341234-1234-1234-1234-123412341234"
+    mock_elements_worker.corpus_id = "12341234-1234-1234-1234-123412341234"
     mock_elements_worker.classes = {
-        "11111111-1111-1111-1111-111111111111": {"good": "0000"}
+        "12341234-1234-1234-1234-123412341234": {"good": "0000"}
     }
 
     ml_class_id = mock_elements_worker.get_ml_class_id("good")
@@ -86,12 +86,12 @@ def test_get_ml_class_id(mock_elements_worker):
 
 
 def test_get_ml_class_reload(responses, mock_elements_worker):
-    corpus_id = mock_elements_worker.corpus_id
+    mock_elements_worker.corpus_id = "12341234-1234-1234-1234-123412341234"
 
     # Add some initial classes
     responses.add(
         responses.GET,
-        f"http://testserver/api/v1/corpus/{corpus_id}/classes/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/",
         json={
             "count": 1,
             "next": None,
@@ -107,7 +107,7 @@ def test_get_ml_class_reload(responses, mock_elements_worker):
     # Invalid response when trying to create class2
     responses.add(
         responses.POST,
-        f"http://testserver/api/v1/corpus/{corpus_id}/classes/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/",
         status=400,
         json={"non_field_errors": "Already exists"},
     )
@@ -115,7 +115,7 @@ def test_get_ml_class_reload(responses, mock_elements_worker):
     # Add both classes (class2 is created by another process)
     responses.add(
         responses.GET,
-        f"http://testserver/api/v1/corpus/{corpus_id}/classes/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/",
         json={
             "count": 2,
             "next": None,
@@ -137,7 +137,7 @@ def test_get_ml_class_reload(responses, mock_elements_worker):
 
     assert len(responses.calls) == len(BASE_API_CALLS) + 3
     assert mock_elements_worker.classes == {
-        corpus_id: {
+        mock_elements_worker.corpus_id: {
             "class1": "class1_id",
             "class2": "class2_id",
         }
@@ -145,9 +145,9 @@ def test_get_ml_class_reload(responses, mock_elements_worker):
     assert [
         (call.request.method, call.request.url) for call in responses.calls
     ] == BASE_API_CALLS + [
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
-        ("POST", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
+        ("POST", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
     ]
 
 
diff --git a/tests/test_elements_worker/test_elements.py b/tests/test_elements_worker/test_elements.py
index 05aac1300f56564d3b3732a3173a69cbaad0d61c..6ad91b512d877510372539bdb6431f5222799c5b 100644
--- a/tests/test_elements_worker/test_elements.py
+++ b/tests/test_elements_worker/test_elements.py
@@ -32,12 +32,12 @@ def test_check_required_types_argument_types(mock_elements_worker):
 
 
 def test_check_required_types(responses, mock_elements_worker):
-    corpus_id = mock_elements_worker.corpus_id
+    mock_elements_worker.corpus_id = "12341234-1234-1234-1234-123412341234"
     responses.add(
         responses.GET,
-        f"http://testserver/api/v1/corpus/{corpus_id}/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/",
         json={
-            "id": corpus_id,
+            "id": mock_elements_worker.corpus_id,
             "name": "Some Corpus",
             "types": [{"slug": "folder"}, {"slug": "page"}],
         },
@@ -51,18 +51,18 @@ def test_check_required_types(responses, mock_elements_worker):
         assert mock_elements_worker.check_required_types("page", "text_line", "act")
     assert (
         str(e.value)
-        == "Element type(s) act, text_line were not found in the Some Corpus corpus (11111111-1111-1111-1111-111111111111)."
+        == "Element type(s) act, text_line were not found in the Some Corpus corpus (12341234-1234-1234-1234-123412341234)."
     )
 
 
 def test_create_missing_types(responses, mock_elements_worker):
-    corpus_id = mock_elements_worker.corpus_id
+    mock_elements_worker.corpus_id = "12341234-1234-1234-1234-123412341234"
 
     responses.add(
         responses.GET,
-        f"http://testserver/api/v1/corpus/{corpus_id}/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/",
         json={
-            "id": corpus_id,
+            "id": mock_elements_worker.corpus_id,
             "name": "Some Corpus",
             "types": [{"slug": "folder"}, {"slug": "page"}],
         },
@@ -76,7 +76,7 @@ def test_create_missing_types(responses, mock_elements_worker):
                     "slug": "text_line",
                     "display_name": "text_line",
                     "folder": False,
-                    "corpus": corpus_id,
+                    "corpus": mock_elements_worker.corpus_id,
                 }
             )
         ],
@@ -90,7 +90,7 @@ def test_create_missing_types(responses, mock_elements_worker):
                     "slug": "act",
                     "display_name": "act",
                     "folder": False,
-                    "corpus": corpus_id,
+                    "corpus": mock_elements_worker.corpus_id,
                 }
             )
         ],
@@ -271,10 +271,10 @@ def test_database_arg_cache_missing_version_table(
 
 
 def test_load_corpus_classes_api_error(responses, mock_elements_worker):
-    corpus_id = mock_elements_worker.corpus_id
+    mock_elements_worker.corpus_id = "12341234-1234-1234-1234-123412341234"
     responses.add(
         responses.GET,
-        f"http://testserver/api/v1/corpus/{corpus_id}/classes/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/",
         status=500,
     )
 
@@ -289,20 +289,20 @@ def test_load_corpus_classes_api_error(responses, mock_elements_worker):
         (call.request.method, call.request.url) for call in responses.calls
     ] == BASE_API_CALLS + [
         # We do 5 retries
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
     ]
     assert not mock_elements_worker.classes
 
 
 def test_load_corpus_classes(responses, mock_elements_worker):
-    corpus_id = mock_elements_worker.corpus_id
+    mock_elements_worker.corpus_id = "12341234-1234-1234-1234-123412341234"
     responses.add(
         responses.GET,
-        f"http://testserver/api/v1/corpus/{corpus_id}/classes/",
+        f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/",
         status=200,
         json={
             "count": 3,
@@ -331,10 +331,10 @@ def test_load_corpus_classes(responses, mock_elements_worker):
     assert [
         (call.request.method, call.request.url) for call in responses.calls
     ] == BASE_API_CALLS + [
-        ("GET", f"http://testserver/api/v1/corpus/{corpus_id}/classes/"),
+        ("GET", f"http://testserver/api/v1/corpus/{mock_elements_worker.corpus_id}/classes/"),
     ]
     assert mock_elements_worker.classes == {
-        "11111111-1111-1111-1111-111111111111": {
+        "12341234-1234-1234-1234-123412341234": {
             "good": "0000",
             "average": "1111",
             "bad": "2222",