prevent duplicate assembly steps

fixes #27

CHANGELOG.md

@@ -1,3 +1,7 @@
+### 3.0.0 / ????-??-?? ###
+
+* Prevent duplicate assembly steps [#49](https://github.com/transloadit/ruby-sdk/issues/27) (@ifedapoolarewaju)
+
 ### 2.0.1 / 2017-01-23 ###
 
 * Use the ssl enabled url as the API base url (@ifedapoolarewaju)

lib/transloadit/assembly.rb

@@ -144,6 +144,9 @@ def _wrap_steps_in_hash(steps)
       when Hash               then steps
       when Transloadit::Step  then steps.to_hash
       else
+        if steps.uniq(&:name) != steps
+          raise ArgumentError, "There are different Assembly steps using the same name"
+        end
         steps.inject({}) {|h, s| h.update s }
     end
   end

test/unit/test_transloadit.rb

@@ -75,8 +75,8 @@
 
     it 'must create assemblies with multiple steps' do
       steps = [
-        @transloadit.step(nil, nil),
-        @transloadit.step(nil, nil),
+        @transloadit.step('step1', nil),
+        @transloadit.step('step2', nil),
       ]
 
       assembly = @transloadit.assembly :steps => steps

test/unit/transloadit/test_assembly.rb

@@ -168,6 +168,15 @@
       @assembly.to_hash[:steps].keys.must_include @encode.name
       @assembly.to_hash[:steps].keys.must_include @thumbs.name
     end
+
+    it 'must not allow duplicate steps' do
+      thumbs = @transloadit.step('thumbs', '/video/thumbs')
+      thumbs_duplicate = @transloadit.step('thumbs', '/video/encode')
+      options = { :steps => [ thumbs, thumbs_duplicate ] }
+      assert_raises ArgumentError do
+        response = @assembly.create! open('lib/transloadit/version.rb'), options
+      end
+    end
   end
 
   describe 'using assembly API methods' do