test(logic): describe base64/2 feature

Author: ccamel

x/logic/predicate/features/base64_2.feature

@@ -0,0 +1,28 @@
+Feature: base64/2
+  This feature is to test the base64/2 predicate.
+
+  @great_for_documentation
+  Scenario: Encode and decode a string into a Base64 encoded atom
+  This scenario demonstrates how to encode an decode a plain string into a Base64-encoded atom using the `base64/2`
+  predicate.
+
+    Given the query:
+      """ prolog
+      base64url('Hello world', Encoded),
+      base64url(Decoded, 'SGVsbG8gd29ybGQ').
+      """
+    When the query is run
+    Then the answer we get is:
+      """ yaml
+      height: 42
+      gas_used: 3976
+      answer:
+        has_more: false
+        variables: ["Encoded", "Decoded"]
+        results:
+        - substitutions:
+          - variable: Encoded
+            expression: "'SGVsbG8gd29ybGQ'"
+          - variable: Decoded
+            expression: "'Hello world'"
+      """