Add gherkin tests to verify evaluation details in finally hooks

specification/assets/gherkin/evaluation.feature

@@ -3,7 +3,7 @@ Feature: Flag evaluation
 # This test suite contains scenarios to test the flag evaluation API.
 
   Background:
-    Given a provider is registered
+    Given a stable provider
 
   # basic evaluation
   Scenario: Resolves boolean value

specification/assets/gherkin/hooks.feature

@@ -0,0 +1,49 @@
+@hooks
+Feature: Evaluation details through hooks
+
+# This test suite contains scenarios to test the functionality of hooks.
+
+  Background:
+    Given a stable provider
+
+  Scenario: Passes evaluation details to after and finally hooks
+    Given a client with added hook
+    And a boolean-flag with key "boolean-flag" and a default value "false"
+    When the flag was evaluated with details
+    Then the "before" hook should have been executed
+    And the "after, finally after" hooks should be called with evaluation details
+      | data_type | key           | value        |
+      | string    | flag_key      | boolean-flag |
+      | boolean   | value         | true         |
+      | string    | variant       | on           |
+      | string    | reason        | STATIC       |
+      | string    | error_code    | None         |
+
+  # errors
+  Scenario: Flag not found
+    Given a client with added hook
+    And a string-flag with key "missing-flag" and a default value "uh-oh"
+    When the flag was evaluated with details
+    Then the "before" hook should have been executed
+    And the "error" hook should have been executed
+    And the "finally after" hooks should be called with evaluation details
+      | data_type | key           | value                         |
+      | string    | flag_key      | missing-flag                  |
+      | string    | value         | uh-oh                         |
+      | string    | variant       | None                          |
+      | string    | reason        | ERROR                         |
+      | string    | error_code    | ErrorCode.FLAG_NOT_FOUND      |
+
+  Scenario: Type error
+    Given a client with added hook
+    And a string-flag with key "wrong-flag" and a default value "13"
+    When the flag was evaluated with details
+    Then the "before" hook should have been executed
+    And the "error" hook should have been executed
+    And the "finally after" hooks should be called with evaluation details
+      | data_type | key           | value                                             |
+      | string    | flag_key      | wrong-flag                                        |
+      | integer   | value         | 13                                                |
+      | string    | variant       | None                                              |
+      | string    | reason        | ERROR                                             |
+      | string    | error_code    | ErrorCode.TYPE_MISMATCH                           |