Check for presence of an MP in local JSON data

Now that parliament has been dissolved all constituencies have no
sitting MP so make sure that we don't try to output one.

Author: pixeltrix

app/views/local_petitions/_petitions.json.jbuilder

@@ -1,8 +1,10 @@
 json.constituency constituency.name
 
-json.mp do
-  json.name constituency.mp_name
-  json.url constituency.mp_url
+if constituency.sitting_mp?
+  json.mp do
+    json.name constituency.mp_name
+    json.url constituency.mp_url
+  end
 end
 
 json.petitions petitions do |petition|

features/freya_searches_for_petitions_by_constituency.feature

@@ -100,3 +100,47 @@ Feature: Freya searches petitions by constituency
     And I search for petitions local to me in "S4 8AA"
     Then the markup should be valid
     And I should not see a link to the MP for my constituency
+
+  Scenario: Downloading the JSON data for open local petitions when the mp has passed away
+    Given a constituency "Sheffield, Brightside and Hillsborough" with MP "Harry Harpham" is found by postcode "S4 8AA"
+    And the MP has passed away
+    When I am on the home page
+    And I search for petitions local to me in "S4 8AA"
+    Then the markup should be valid
+    When I click the JSON link
+    Then I should be on the local petitions JSON page
+    And the JSON should be valid
+
+  Scenario: Downloading the JSON data for all local petitions when the mp has passed away
+    Given a constituency "Sheffield, Brightside and Hillsborough" with MP "Harry Harpham" is found by postcode "S4 8AA"
+    And the MP has passed away
+    When I am on the home page
+    And I search for petitions local to me in "S4 8AA"
+    Then the markup should be valid
+    When I click the view all local petitions
+    Then I should be on the all local petitions results page
+    And the markup should be valid
+    When I click the JSON link
+    Then I should be on the all local petitions JSON page
+    And the JSON should be valid
+
+  Scenario: Downloading the CSV data for local petitions when the mp has passed away
+    Given a constituency "Sheffield, Brightside and Hillsborough" with MP "Harry Harpham" is found by postcode "S4 8AA"
+    And the MP has passed away
+    When I am on the home page
+    And I search for petitions local to me in "S4 8AA"
+    Then the markup should be valid
+    When I click the CSV link
+    Then I should get a download with the filename "open-popular-petitions-in-sheffield-brightside-and-hillsborough.csv"
+
+  Scenario: Downloading the CSV data for local petitions when the mp has passed away
+    Given a constituency "Sheffield, Brightside and Hillsborough" with MP "Harry Harpham" is found by postcode "S4 8AA"
+    And the MP has passed away
+    When I am on the home page
+    And I search for petitions local to me in "S4 8AA"
+    Then the markup should be valid
+    When I click the view all local petitions
+    Then I should be on the all local petitions results page
+    And the markup should be valid
+    When I click the CSV link
+    Then I should get a download with the filename "all-popular-petitions-in-sheffield-brightside-and-hillsborough.csv"