diff --git a/unittests/test_variable_substitutions.py b/unittests/test_variable_substitutions.py
index 0df761d400524b1883b3bde31882b205940888e7..a1af700a581e8234b6e03a70f15cb71a2d046d81 100644
--- a/unittests/test_variable_substitutions.py
+++ b/unittests/test_variable_substitutions.py
@@ -24,6 +24,7 @@ def rfp(*pathcomponents):
     """
     return join(dirname(__file__), *pathcomponents)
 
+
 def dircheckstr(element_type, *pathcomponents):
     """
     Return the debug tree identifier for a given path.
@@ -41,14 +42,19 @@ def crawler():
 
 def test_substitutions(crawler):
     for i in range(2):
-        subd = crawler.debug_tree[dircheckstr("File", "ExperimentalData", "220512_data.dat")]
+        subd = crawler.debug_tree[dircheckstr(
+            "File", "ExperimentalData", "220512_data.dat")]
         assert subd[i]["Experiment"].get_property("date").value == "2022-05-12"
-        assert isinstance(subd[i]["ExperimentSeries"].get_property("Experiment").value, db.Record)
+        assert isinstance(subd[i]["ExperimentSeries"].get_property(
+            "Experiment").value, db.Record)
 
         subd = crawler.debug_tree[dircheckstr("Directory", "ExperimentalData")]
         assert subd[i]["Project"].name == "project"
-        assert isinstance(subd[i]["Project"].get_property("Experiments").value, list)
-        assert isinstance(subd[i]["Project"].get_property("Experiments").value[0], db.Record)
+        assert isinstance(subd[i]["Project"].get_property(
+            "Experiments").value, list)
+        assert isinstance(subd[i]["Project"].get_property(
+            "Experiments").value[0], db.Record)
 
         assert isinstance(subd[i]["Project"].get_property("dates").value, list)
-        assert subd[i]["Project"].get_property("dates").value[0] == "2022-05-12"
+        assert subd[i]["Project"].get_property(
+            "dates").value[0] == "2022-05-12"