New error handling in poc and features

spec/test/features/control/append/error_malformed.feature

@@ -28,4 +28,10 @@ Feature: Kapow! server reject append requests with malformed JSON bodies.
       Hi! I am an invalid JSON document.
       """
     Then I get 400 as response code
-      And I get "Malformed JSON" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Malformed JSON"
+      }
+      """

spec/test/features/control/append/error_unprocessable.feature

@@ -31,7 +31,13 @@ Feature: Kapow! server rejects requests with semantic errors.
       }
       """
     Then I get 422 as response code
-      And I get "Invalid Route" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Invalid Route"
+      }
+      """
 
   Scenario: Error because bad route format.
     If a request contains an invalid expression in the
@@ -48,4 +54,10 @@ Feature: Kapow! server rejects requests with semantic errors.
       }
       """
     Then I get 422 as response code
-      And I get "Invalid Route" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Invalid Route"
+      }
+      """

spec/test/features/control/delete/error_notfound.feature

@@ -24,4 +24,10 @@ Feature: Fail to delete a route in Kapow! server.
     Given I have a just started Kapow! server
     When I delete the route with id "xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx"
     Then I get 404 as response code
-      And I get "Not Found" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Route Not Found"
+      }
+      """

spec/test/features/control/get/error_notfound.feature

@@ -24,4 +24,10 @@ Feature: Fail to retrieve route details in Kapow! server.
     Given I have a just started Kapow! server
     When I get the route with id "xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx"
     Then I get 404 as response code
-      And I get "Not Found" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Route Not Found"
+      }
+      """

spec/test/features/control/insert/error_malformed.feature

@@ -37,4 +37,10 @@ Feature: Kapow! server rejects insertion requests with malformed JSON bodies.
       }
       """
     Then I get 400 as response code
-      And I get "Malformed JSON" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Malformed JSON"
+      }
+      """

spec/test/features/control/insert/error_unprocessable.feature

@@ -67,4 +67,10 @@ Feature: Kapow! server rejects insertion requests with semantic errors.
       }
       """
     Then I get 422 as response code
-      And I get "Invalid Route" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Invalid Route"
+      }
+      """

spec/test/features/data/handler/error_handleridnotfound.feature

@@ -25,4 +25,10 @@ Feature: Fail to retrieve resources from nonexistent handler in Kapow! server.
     Given I have a running Kapow! server
     When I get the resource "/request/path" for the handler with id "XXXXXXXXXX"
     Then I get 404 as response code
-      And I get "Handler ID Not Found" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Handler ID Not Found"
+      }
+      """

spec/test/features/data/handler/error_invalidresource.feature

@@ -27,4 +27,10 @@ Feature: Fail to retrieve an invalid resource for a handler in Kapow! server.
     When I send a request to the testing route "/foo"
       And I get the resource "/invented/path"
     Then I get 400 as response code
-      And I get "Invalid Resource Path" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Invalid Resource Path"
+      }
+      """

spec/test/features/data/handler/error_itemnotfound.feature

@@ -28,4 +28,10 @@ Feature: Fail to retrieve nonexistent resource items in Kapow! server.
     When I send a request to the testing route "/foo"
       And I get the resource "/request/params/meloinvento"
     Then I get 404 as response code
-      And I get "Resource Item Not Found" as response reason phrase
+      And the response header "Content-Type" contains "application/json"
+      And I get the following response body:
+      """
+      {
+        "reason": "Resource Item Not Found"
+      }
+      """

spec/test/features/steps/steps.py

@@ -185,6 +185,16 @@ def step_impl(context, code):
     assert context.testing_response.status_code == int(code), f"Got {context.testing_response.status_code} instead"
 
 
+@then('the response header {header_name} contains {value}')
+def step_impl(context, header_name, value):
+    assert context.response.headers.get(header_name) == value, f"Got {context.response.headers.get(header_name)} instead"
+
+
+@then('the testing response header {header_name} contains {value}')
+def step_impl(context, header_name, value):
+    assert context.testing_response.headers.get(header_name) == value, f"Got {context.testing_response.headers.get(header_name)} instead"
+
+
 @then('I get "{reason}" as response reason phrase')
 def step_impl(context, reason):
     assert context.response.reason == reason, f"Got {context.response.reason} instead"