Begin writing about acceptance testing

Author: craigjbass

learn/basics/start-with-acceptance.md

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+# Start with Acceptance Testing
+
+
+Acceptance testing is where you should start before writing anything. 
+Similarly, if in doubt, always check your acceptance tests and go from there.
+
+Here, we're going to be describing something that looks like the A in [ATDD](https://en.wikipedia.org/wiki/Acceptance_test%E2%80%93driven_development), with [BDD](https://en.wikipedia.org/wiki/Behavior-driven_development) in the mix too.
+
+## What is an acceptance test?
+
+It is a high-level set of tests, written from the perspective of the user, showing clear steps through the step.
+
+In BDD the behaviour of the system might be defined light so: 
+
+```cucumber
+Given the light is off
+When I turn the light on
+Then the light is on
+```
+
+Here is the same Cumcumber script written as RSpec Ruby:
+
+```ruby
+describe 'lighting' do
+ let(:system) { LightingSystem.new }
+ let(:create_light_use_case) { system.get_use_case(:create_light) }
+ let(:turn_light_on_use_case) { system.get_use_case(:turn_light_on) }
+ let(:view_light_status_use_case) { system.get_use_case(:view_light_status) }
+ 
+ let(:light_id) do
+ response = create_light_use_case.execute
+ response[:id]
+ end
+ 
+ let(:view_light_status_response) do
+ view_light_status_use_case.execute(light_id: light_id)
+ end
+ 
+ context 'given the light is off' do
+ it 'is off' do
+ expect(view_light_status_response[:on]).to be(false)
+ end
+ 
+ context 'when I turn the light on' do
+ before { turn_light_on_use_case.execute(light_id: light_id) } 
+ 
+ it 'is on' do
+ expect(view_light_status_response[:on]).to be(true)
+ end
+ end
+ end
+end
+```