diff --git a/autoform_cli/scaffold.py b/autoform_cli/scaffold.py
index 0bd85682..2244f193 100644
--- a/autoform_cli/scaffold.py
+++ b/autoform_cli/scaffold.py
@@ -355,9 +355,7 @@ def _committed_scaffold_entries(
 
 
 def _git_blob_id(content: bytes, length: int) -> str | None:
-    algorithm = {40: "sha1", 64: "sha256"}.get(length)
-    if algorithm is None:
-        return None
+    algorithm = {40: "sha1", 64: "sha256"}[length]
     try:
         digest = hashlib.new(algorithm, usedforsecurity=False)
     except ValueError:
diff --git a/tests/test_project_create.py b/tests/test_project_create.py
index 6ab210d9..1a992cc9 100644
--- a/tests/test_project_create.py
+++ b/tests/test_project_create.py
@@ -424,11 +424,7 @@ def test_open_parent_descriptor_rechecks_the_generated_module_filename_limit(
 
 
 def test_rejects_unknown_release_before_writing(tmp_path: Path) -> None:
-    target = tmp_path / "project"
-    with pytest.raises(ProjectCreateError) as raised:
-        create_project(target, package="Project", release_id="unknown")
-    assert raised.value.code == "project-release-unknown"
-    assert not target.exists()
+    _refused(tmp_path / "project", "project-release-unknown", release_id="unknown")
 
 
 def test_omitted_release_uses_the_recommended_release(tmp_path: Path) -> None:
@@ -840,12 +836,7 @@ def corrupt(*args, **kwargs):
 
     monkeypatch.setattr(create_module, "_build_project_plan", corrupt)
 
-    with pytest.raises(ProjectCreateError) as raised:
-        create_project(target, package="Project", release_id=_RELEASE)
-
-    assert raised.value.code == "project-create-validation-failed"
-    assert not target.exists()
-    assert not list(tmp_path.glob(".autoform-new-*"))
+    _refused(target, "project-create-validation-failed")
 
 
 @pytest.mark.parametrize("corruption", ["container", "relative", "content", "mode"])
@@ -1719,12 +1710,7 @@ def test_group_writable_parent_is_refused_with_a_remedy(tmp_path: Path) -> None:
     parent.mkdir(mode=0o700)
     parent.chmod(0o775)
 
-    with pytest.raises(ProjectCreateError) as raised:
-        create_project(parent / "Project", package="Project", release_id=_RELEASE)
-
-    assert raised.value.code == "project-parent-unsafe"
-    assert "chmod g-w,o-w" in raised.value.message
-    assert not list(parent.iterdir())
+    assert "chmod g-w,o-w" in _refused(parent / "Project", "project-parent-unsafe").message
 
 
 _NEEDS_PERMISSIONS = pytest.mark.skipif(