diff --git a/bin/tools.py b/bin/tools.py
index d1de3ca7..3c0c258f 100755
--- a/bin/tools.py
+++ b/bin/tools.py
@@ -448,9 +448,7 @@ def build_parser():
     input_answer_group.add_argument(
         '--input', '-i', action='store_true', help='Only validate input.'
     )
-    input_answer_group.add_argument(
-        '--answer', action='store_true', help='Only validate answer.'
-    )
+    input_answer_group.add_argument('--answer', action='store_true', help='Only validate answer.')
     input_answer_group.add_argument(
         '--invalid', action='store_true', help='Only check invalid files for validity.'
     )
diff --git a/bin/validate.py b/bin/validate.py
index 5004efc6..5cdfc93d 100644
--- a/bin/validate.py
+++ b/bin/validate.py
@@ -100,7 +100,12 @@ def _run_helper(self, testcase, constraints, args):
             cwd = testcase.in_path.with_suffix('.feedbackdir')
         else:
             name = self.tmpdir.relative_to(self.problem.tmpdir)
-            cwd = self.problem.tmpdir / 'tool_runs' / name / testcase.short_path.with_suffix('.feedbackdir')
+            cwd = (
+                self.problem.tmpdir
+                / 'tool_runs'
+                / name
+                / testcase.short_path.with_suffix('.feedbackdir')
+            )
         cwd.mkdir(parents=True, exist_ok=True)
         arglist = []
         if args is not None:
diff --git a/doc/validation.md b/doc/validation.md
index f2e96c57..37859d28 100644
--- a/doc/validation.md
+++ b/doc/validation.md
@@ -171,5 +171,3 @@ For interactive problems (`validation: custom interactive`), the invocation is
 the same as above, but `stdin` is a pipe that feeds team output into the
 validator instead of a file.
 Similarly, `stdout` is connected to a pipe that forwards to the submission's `stdin`.
-
-
diff --git a/skel/testing_tool.py b/skel/testing_tool.py
index c493130d..6a1ae7ea 100644
--- a/skel/testing_tool.py
+++ b/skel/testing_tool.py
@@ -58,9 +58,7 @@ def read(p):
     return line
 
 
-parser = argparse.ArgumentParser(
-    description="Testing tool for problem Ducky Debugging."
-)
+parser = argparse.ArgumentParser(description="Testing tool for problem XXX.")  # TODO update name
 parser.add_argument(
     "-f",
     dest="inputfile",
@@ -117,12 +115,8 @@ def type(x, y):
                 assert 1 <= x2 and x2 <= w, "Point not in bounds"
                 assert 1 <= y2 and y2 <= h, "Point not in bounds"
                 assert (x1, y1) != (x2, y2)
-                assert (
-                    type(x1, y1) == "horizon"
-                ), "First point does not lie on the horizon."
-                assert (
-                    type(x2, y2) == "horizon"
-                ), "First point does not lie on the horizon."
+                assert type(x1, y1) == "horizon", "First point does not lie on the horizon."
+                assert type(x2, y2) == "horizon", "First point does not lie on the horizon."
                 break
             else:
                 assert False, "Line does not start with question or exclamation mark."
diff --git a/support/schemas/generators.cue b/support/schemas/generators.cue
index f3617783..aad46fee 100644
--- a/support/schemas/generators.cue
+++ b/support/schemas/generators.cue
@@ -7,7 +7,7 @@ package problemformat
 import "struct"
 
 // A command invokes a generator, like "tree --n 5".
-// The regex restricts occurrences of curly-bracked expressions 
+// The regex restricts occurrences of curly-bracketed expressions
 // to things like "tree --random --seed {seed:5}"
 command: !="" & (=~"^[^{}]*(\\{seed(:[0-9]+)?\\}[^{}]*)*$")
 
@@ -16,7 +16,7 @@ command: !="" & (=~"^[^{}]*(\\{seed(:[0-9]+)?\\}[^{}]*)*$")
 let basename = "([A-Za-z0-9][A-Za-z0-9_-]*[A-Za-z0-9]|[A-Za-z0-9])"
 name: =~"^\(basename)$"
 
-// Filenames are somewhat like names, but can also contain '.' 
+// Filenames are somewhat like names, but can also contain '.'
 // and have length at least 2, such as "good-solution_02.py"
 // but not "huge_" or "a".
 let filename = "[A-Za-z0-9][A-Za-z0-9_.-]*[A-Za-z0-9]"
diff --git a/support/schemas/testdata.cue b/support/schemas/testdata.cue
index 33c78773..162dd06f 100644
--- a/support/schemas/testdata.cue
+++ b/support/schemas/testdata.cue
@@ -17,7 +17,7 @@ import "strconv"
 	reject_score: *"0" | #score
 	range: *"-inf +inf" | string
     // Verify that the scores and ranges make sense:
-    _range_syntax: strings.Split(range, " ") & [#score, #score] // space-separated scores  
+    _range_syntax: strings.Split(range, " ") & [#score, #score] // space-separated scores
     _lo: strconv.ParseFloat(strings.Split(range, " ")[0], 64)   // parses to float (including '-inf')
     _hi: strconv.ParseFloat(strings.Split(range, " ")[1], 64)
     _wa: strconv.ParseFloat(reject_score, 64)
@@ -25,13 +25,13 @@ import "strconv"
     _order: true & _lo <= _wa  & _wa <= _ac & _ac <= _hi
 }
 // matches "1", "06", "21", ".4", "-1.2", but not 'inf'
-#score: =~ "^-?([0-9]+|[0-9]*.[0-9]+)$" 
+#score: =~ "^-?([0-9]+|[0-9]*.[0-9]+)$"
 
 // Default grader
 // --------------
 
 #default_grader_flags: this={
-    string  
+    string
     _as_struct: { for w in strings.Split(this, " ")  { (w): _ } }  // convert to struct and ...
     _as_struct: #valid_default_grader_fields                       // ... validate its fields
     }
@@ -45,4 +45,4 @@ import "strconv"
 }
 
 #verdict_aggregation_mode: {first_error: _ } | *{worst_error: _  } | {always_accept: _ }
-#score_aggregation_mode:  {min: _ } | {max: _ } | *{sum: _ } | {avg: _ }
\ No newline at end of file
+#score_aggregation_mode:  {min: _ } | {max: _ } | *{sum: _ } | {avg: _ }