AO3-6625 Test more spacing and use more succinct code

app/models/download.rb

@@ -54,12 +54,9 @@ def file_type_from_mime(mime)
   # The base name of the file (e.g., "War_and_Peace")
   def file_name
     name = clean(work.title)
-    extender = "Work_#{work.id}"
-    if name.length.zero?
-      name = extender
-    elsif name.length < 3
-      name += "_#{extender}"
-    end
+    # If the file name is 1-2 characters, append "_Work_#{work.id}".
+    # If the file name is blank, name the file "Work_#{work.id}".
+    name = [name, "Work_#{work.id}"].compact_blank.join("_") if name.length < 3
     name.strip
   end
 

spec/models/download_spec.rb

@@ -36,6 +36,62 @@
       expect(Download.new(work).file_name).to eq("Emjoi_Yay")
     end
 
+    it "strips leading space" do
+      work.title = " Blank Space Baby"
+      expect(Download.new(work).file_name).to eq("Blank_Space_Baby")
+    end
+
+    it "strips trailing space" do
+      work.title = "Write your name: "
+      expect(Download.new(work).file_name).to eq("Write_your_name")
+    end
+
+    it "replaces multiple spaces with single underscore" do
+      work.title = "Space   Opera"
+      expect(Download.new(work).file_name).to eq("Space_Opera")
+    end
+
+    it "replaces unicode space with underscores" do
+      work.title = "No-break Space"
+      expect(Download.new(work).file_name).to eq("No-break_Space")
+
+      work.title = "En Quad Space"
+      expect(Download.new(work).file_name).to eq("En_Quad_Space")
+
+      work.title = "Em Quad Space"
+      expect(Download.new(work).file_name).to eq("Em_Quad_Space")
+
+      work.title = "En Space"
+      expect(Download.new(work).file_name).to eq("En_Space")
+
+      work.title = "Em Space"
+      expect(Download.new(work).file_name).to eq("Em_Space")
+
+      work.title = "3 Per Em Space"
+      expect(Download.new(work).file_name).to eq("3_Per_Em_Space")
+
+      work.title = "4 Per Em Space"
+      expect(Download.new(work).file_name).to eq("4_Per_Em_Space")
+
+      work.title = "6 Per Em Space"
+      expect(Download.new(work).file_name).to eq("6_Per_Em_Space")
+
+      work.title = "Figure Space"
+      expect(Download.new(work).file_name).to eq("Figure_Space")
+
+      work.title = "Punctuation Space"
+      expect(Download.new(work).file_name).to eq("Punctuation_Space")
+
+      work.title = "Thin Space"
+      expect(Download.new(work).file_name).to eq("Thin_Space")
+
+      work.title = "Hair Space"
+      expect(Download.new(work).file_name).to eq("Hair_Space")
+
+      work.title = "Narrow No-Break Space"
+      expect(Download.new(work).file_name).to eq("Narrow_No-Break_Space")
+    end
+
     it "appends work ID if too short" do
       work.id = 999_999
       work.title = "Uh"