Attending rubocop and improving tests

lib/webpacker/helper.rb

@@ -101,16 +101,18 @@ def javascript_pack_tag(*names, defer: true, **options)
       @emitted = {}
     end
     includetags = "".html_safe
+    newline = "".html_safe
     sources = sources_from_manifest_entrypoints(names, type: :javascript)
     sources.each do |source|
-      if @emitted.keys.include?(source) && @emitted[source][:defer] != defer
+      if @emitted.key?(source) && @emitted[source][:defer] != defer
         raise "Chunk #{source} already emitted with defer value "\
           "#{@emitted[source][:defer]}. Trying to emit with different "\
           "defer value is not allowed."
-      elsif !@emitted.keys.include?(source)
-        includetags += javascript_include_tag(source, options)
+      elsif !@emitted.key?(source)
+        includetags += newline + javascript_include_tag(source, options)
       end
-      @emitted[source] = {defer: defer}
+      @emitted[source] = { defer: defer }
+      newline = "\n".html_safe
     end
     return includetags
   end

test/helper_test.rb

@@ -106,12 +106,13 @@ def test_javascript_pack_tag
       javascript_pack_tag("application", "bootstrap")
   end
 
-  def test_javascript_pack_with_no_defer_tag
-    assert_equal \
-      %(<script src="/packs/vendors~application~bootstrap-c20632e7baf2c81200d3.chunk.js"></script>\n) +
+  SCRIPTS_APPLICATION_BOOTSTRAP = %(<script src="/packs/vendors~application~bootstrap-c20632e7baf2c81200d3.chunk.js"></script>\n) +
         %(<script src="/packs/vendors~application-e55f2aae30c07fb6d82a.chunk.js"></script>\n) +
         %(<script src="/packs/application-k344a6d59eef8632c9d1.js"></script>\n) +
-        %(<script src="/packs/bootstrap-300631c4f0e0f9c865bc.js"></script>),
+        %(<script src="/packs/bootstrap-300631c4f0e0f9c865bc.js"></script>)
+
+  def test_javascript_pack_with_no_defer_tag
+    assert_equal SCRIPTS_APPLICATION_BOOTSTRAP,
       javascript_pack_tag("application", "bootstrap", defer: false)
   end
 
@@ -132,15 +133,10 @@ def test_javascript_pack_tag_symbol
   end
 
   def test_javascript_pack_tag_multiple_invocations
-    error = assert_raises do
-      javascript_pack_tag(:application)
-      javascript_pack_tag(:bootstrap)
-    end
+    r = javascript_pack_tag(:application, defer: false)
+    r += "\n".html_safe + javascript_pack_tag(:bootstrap, defer: false)
 
-    assert_equal \
-      "To prevent duplicated chunks on the page, you should call javascript_pack_tag only once on the page. " +
-        "Please refer to https://github.com/shakacode/shakapacker/blob/master/README.md#usage for the usage guide",
-      error.message
+    assert_equal SCRIPTS_APPLICATION_BOOTSTRAP, r
   end
 
   def application_stylesheet_chunks