diff --git a/app/services/find_not_expected_bibs.rb b/app/services/find_not_expected_bibs.rb
index 29262d3f6..bdd383846 100644
--- a/app/services/find_not_expected_bibs.rb
+++ b/app/services/find_not_expected_bibs.rb
@@ -1,22 +1,22 @@
-require "ostruct"
-
 class FindNotExpectedBibs
   include Interactors::Errors
   include SplitAnalyzable
 
+  Response = Struct.new(:errors, :bib_numbers, keyword_init: true)
+
   def self.perform(event_group, split_name)
     new(event_group, split_name).perform
   end
 
   def initialize(event_group, split_name)
     @event_group = event_group
-    @parameterized_split_name = split_name.parameterize
+    @parameterized_split_name = split_name.to_s.parameterize
     @errors = []
     validate_setup
   end
 
   def perform
-    OpenStruct.new(errors: errors, bib_numbers: bib_numbers)
+    Response.new(errors: errors, bib_numbers: bib_numbers)
   end
 
   private
@@ -31,8 +31,8 @@ def bib_numbers
   end
 
   def validate_setup
-    unless parameterized_split_names.include?(parameterized_split_name)
-      errors << invalid_split_name_error(parameterized_split_name, parameterized_split_names)
-    end
+    return if parameterized_split_names.include?(parameterized_split_name)
+
+    errors << invalid_split_name_error(parameterized_split_name, parameterized_split_names)
   end
 end
diff --git a/spec/services/find_not_expected_bibs_spec.rb b/spec/services/find_not_expected_bibs_spec.rb
new file mode 100644
index 000000000..3afd17815
--- /dev/null
+++ b/spec/services/find_not_expected_bibs_spec.rb
@@ -0,0 +1,35 @@
+require "rails_helper"
+
+RSpec.describe FindNotExpectedBibs do
+  subject { described_class.perform(event_group, split_name) }
+
+  let(:event_group) { event_groups(:hardrock_2015) }
+
+  context "when the split name is valid for the event group" do
+    let(:split_name) { "Sherman" }
+
+    it "returns bib numbers without errors" do
+      expect(subject.errors).to be_empty
+      expect(subject.bib_numbers).to be_an(Array)
+    end
+  end
+
+  context "when the split name is not found in the event group" do
+    let(:split_name) { "Nonexistent" }
+
+    it "returns an invalid split name error" do
+      expect(subject.errors.first[:title]).to eq("Invalid split name")
+      expect(subject.bib_numbers).to eq([])
+    end
+  end
+
+  context "when the split name is nil" do
+    let(:split_name) { nil }
+
+    it "returns an invalid split name error instead of raising" do
+      expect { subject }.not_to raise_error
+      expect(subject.errors.first[:title]).to eq("Invalid split name")
+      expect(subject.bib_numbers).to eq([])
+    end
+  end
+end