Improve error message when an example URI is incompatible with request template

lib/pacto/actors/from_examples.rb

@@ -1,4 +1,6 @@
 # -*- encoding : utf-8 -*-
+require 'pacto/errors'
+
 module Pacto
   module Actors
     class FirstExampleSelector
@@ -32,7 +34,7 @@ def build_request(contract, values = {})
         if contract.examples?
           example = @selector.select(contract.examples, values)
           data = contract.request.to_hash
-          request_values.merge! example_uri_values(contract)
+          request_values.merge! example_uri_values(contract, example)
           data['uri'] = contract.request.uri(request_values)
           data['body'] = example.request.body
           data['method'] = contract.request.http_method
@@ -53,11 +55,15 @@ def build_response(contract, values = {})
         end
       end
 
-      def example_uri_values(contract)
+      def example_uri_values(contract,example)
         uri_template = contract.request.pattern.uri_template
-        if contract.examples && contract.examples.values.first[:request][:uri]
-          example_uri = contract.examples.values.first[:request][:uri]
-          uri_template.extract example_uri
+        if example && example[:request][:uri]
+          example_uri = example[:request][:uri]
+          extracted_values = uri_template.extract(example_uri)
+          raise InvalidContract.new([
+                  "Example URI #{example_uri} is not compatible with the request URI template #{uri_template.pattern}"]) unless extracted_values
+          return extracted_values
+
         else
           {}
         end

spec/fabricators/contract_fabricator.rb

@@ -42,7 +42,7 @@
 end
 
 Fabricator(:request_clause, from: REQUEST_CLAUSE_CLASS) do
-  initialize_with { @_klass.new(to_hash.merge(skip_freeze: true)) } # Hash based initialization
+  initialize_with {  @_klass.new(to_hash.merge(skip_freeze: true)) } # Hash based initialization
   host { 'example.com' }
   http_method { 'GET' }
   path { '/abcd' }

spec/unit/actors/from_examples_spec.rb

@@ -24,7 +24,29 @@ module Actors
           generator.build_response contract
         end
       end
-
+      context 'a contract with uri template' do
+        subject(:generator) { described_class.new fallback, Pacto::Actors::NamedExampleSelector }
+        let(:contract) do
+          Fabricate(:contract,
+                    request:
+                      Fabricate(:request_clause,
+                                host: "somewhere.com",
+                                path: "/this_is_something/{b}"),
+                    examples: { "bad" =>
+                      Fabricate(:an_example,
+                                request: {uri: "http://somwer/this_is_not_something/BAD"}),
+                                "good" =>
+                      Fabricate(:an_example,
+                                request: {uri:  "http://somewhere.com/this_is_something/GOOD"})
+                    })
+        end
+        it 'should raise an error if the example uri is incompatible' do
+          expect{generator.build_request(contract, example_name: "bad")}.to raise_error(Pacto::InvalidContract)
+        end
+        it 'should correctly perform substitutions for compatible example uris' do
+          expect(generator.build_request(contract, example_name: "good").uri.to_s).to eq("http://somewhere.com/this_is_something/GOOD")
+        end
+      end
       context 'a contract with examples' do
         let(:contract) { Fabricate(:contract, example_count: 3) }
         let(:request) { generator.build_request contract }