Status code 400 is returned if body is missing on note creation.

lib/api/notes.rb

@@ -43,6 +43,8 @@ module Gitlab
         if @note.save
           present @note, with: Entities::Note
         else
+          # :note is exposed as :body, but :note is set on error
+          error!(@note.errors[:note], 400) if @note.errors[:note].any?
           not_found!
         end
       end

spec/requests/api/notes_spec.rb

@@ -36,6 +36,11 @@ describe Gitlab::API do
       response.status.should == 200
       json_response['body'].should == wall_note.note
     end
+
+    it "should return a 404 error if note not found" do
+      get api("/projects/#{project.id}/notes/123", user)
+      response.status.should == 404
+    end
   end
 
   describe "POST /projects/:id/notes" do
@@ -44,6 +49,11 @@ describe Gitlab::API do
       response.status.should == 201
       json_response['body'].should == 'hi!'
     end
+
+    it "should return a 400 error if body is missing" do
+      post api("/projects/#{project.id}/notes", user)
+      response.status.should == 400
+    end
   end
 
   describe "GET /projects/:id/noteable/:noteable_id/notes" do
@@ -54,6 +64,11 @@ describe Gitlab::API do
         json_response.should be_an Array
         json_response.first['body'].should == issue_note.note
       end
+
+      it "should return a 404 error when issue id not found" do
+        get api("/projects/#{project.id}/issues/123/notes", user)
+        response.status.should == 404
+      end
     end
 
     context "when noteable is a Snippet" do
@@ -63,6 +78,11 @@ describe Gitlab::API do
         json_response.should be_an Array
         json_response.first['body'].should == snippet_note.note
       end
+
+      it "should return a 404 error when snippet id not found" do
+        get api("/projects/#{project.id}/snippets/42/notes", user)
+        response.status.should == 404
+      end
     end
   end
 
@@ -73,6 +93,11 @@ describe Gitlab::API do
         response.status.should == 200
         json_response['body'].should == issue_note.note
       end
+
+      it "should return a 404 error if issue note not found" do
+        get api("/projects/#{project.id}/issues/#{issue.id}/notes/123", user)
+        response.status.should == 404
+      end
     end
 
     context "when noteable is a Snippet" do
@@ -81,6 +106,11 @@ describe Gitlab::API do
         response.status.should == 200
         json_response['body'].should == snippet_note.note
       end
+
+      it "should return a 404 error if snippet note not found" do
+        get api("/projects/#{project.id}/snippets/#{snippet.id}/notes/123", user)
+        response.status.should == 404
+      end
     end
   end