diff --git a/src/ewoksppf/tests/test_ppf_workflow29.py b/src/ewoksppf/tests/test_ppf_workflow29.py
new file mode 100644
index 0000000..892941e
--- /dev/null
+++ b/src/ewoksppf/tests/test_ppf_workflow29.py
@@ -0,0 +1,103 @@
+import os
+import threading
+
+import pytest
+from ewokscore.task import Task
+from ewoksutils.import_utils import qualname
+
+from ewoksppf import execute_graph
+
+_NUM_IMAGES = 100
+_INTEGRATED = list()
+_LOCK = threading.Lock()
+
+
+class InitIntegrator(Task, input_names=["params_file"], output_names=["integrator"]):
+    def run(self):
+        self.outputs.integrator = f"Integrator({self.inputs.params_file})"
+
+
+class FindImages(
+    Task,
+    input_names=["image_directory", "integrator"],
+    optional_input_names=["image_index"],
+    output_names=["image_path", "next_image_index", "finished", "integrator"],
+):
+    def run(self):
+        image_index = self.get_input_value("image_index", 0)
+        self.outputs.image_path = os.path.join(
+            self.inputs.image_directory, f"data{image_index}.tiff"
+        )
+        self.outputs.next_image_index = image_index + 1
+        self.outputs.finished = self.outputs.next_image_index == _NUM_IMAGES
+        self.outputs.integrator = self.inputs.integrator
+
+
+class IntegrateImage(Task, input_names=["integrator", "image_path"]):
+    def run(self):
+        with _LOCK:
+            _INTEGRATED.append((self.inputs.integrator, self.inputs.image_path))
+
+
+def workflow29():
+    nodes = [
+        {
+            "id": "init_integrator",
+            "task_type": "class",
+            "task_identifier": qualname(InitIntegrator),
+        },
+        {
+            "id": "find_images",
+            "task_type": "class",
+            "task_identifier": qualname(FindImages),
+        },
+        {
+            "id": "integrate_image",
+            "task_type": "class",
+            "task_identifier": qualname(IntegrateImage),
+        },
+    ]
+    links = [
+        {
+            "source": "init_integrator",
+            "target": "find_images",
+            "data_mapping": [
+                {"source_output": "integrator", "target_input": "integrator"}
+            ],
+        },
+        {
+            "source": "find_images",
+            "target": "find_images",
+            "data_mapping": [
+                {"source_output": "next_image_index", "target_input": "image_index"},
+            ],
+            "conditions": [{"source_output": "finished", "value": False}],
+        },
+        {
+            "source": "find_images",
+            "target": "integrate_image",
+            "data_mapping": [
+                {"source_output": "image_path", "target_input": "image_path"},
+                {"source_output": "integrator", "target_input": "integrator"},
+            ],
+        },
+    ]
+    return {"graph": {"id": "workflow29"}, "links": links, "nodes": nodes}
+
+
+@pytest.mark.parametrize("scaling_workers", [False, True])
+def test_workflow29(ppf_log_config, scaling_workers):
+    """A self-looping task should be able to iterate many times without
+    a RecursionError or a closed pool (issue #22)."""
+    inputs = [
+        {"id": "init_integrator", "name": "params_file", "value": "calib.poni"},
+        {"id": "find_images", "name": "image_directory", "value": "data"},
+    ]
+    kwargs = {"scaling_workers": True, "max_workers": 2} if scaling_workers else {}
+    _INTEGRATED.clear()
+    execute_graph(workflow29(), inputs=inputs, pool_type="thread", timeout=60, **kwargs)
+    expected = [
+        ("Integrator(calib.poni)", os.path.join("data", f"data{i}.tiff"))
+        for i in range(_NUM_IMAGES)
+    ]
+    assert sorted(_INTEGRATED) == sorted(expected)