Use a private encoder to compare messages, if needed

Source/Message.swift

@@ -31,6 +31,9 @@ public struct Message: Equatable {
         self.metadata = metadata
         self.jsonData = jsonData
     }
+
+    /// Used to compare `jsonData` Strings.
+    private static let equalityJSONEncoder = JSONEncoder()
 }
 
 extension Message {
@@ -94,3 +97,37 @@ extension Message {
         }
     }
 }
+
+extension Message {
+
+    /// Using `Equatable`'s default implementation is bound to give us false positives since two `Message`s may have semantically equal, but textually different, `jsonData`.
+    ///
+    /// For example, the following `jsonData` should be considered equal.
+    ///
+    /// ```
+    /// lhs.jsonData = "{\"title\":\"Page-title\",\"subtitle\":\"Page-subtitle\",\"action_name\":\"go\"}")"
+    ///
+    /// rhs.jsonData = "{\"action_name\":\"go\",\"title\":\"Page-title\",\"subtitle\":\"Page-subtitle\"}")"
+    /// ```
+    ///
+    /// - Parameters:
+    ///   - lhs: a message
+    ///   - rhs: another message
+    /// - Returns: true if they're semantically equal
+    public static func == (lhs: Self, rhs: Self) -> Bool {
+
+        if lhs.jsonData != rhs.jsonData {
+            guard let lhsJSONData = lhs.jsonData.data(using: .utf8),
+                  let rhsJSONData = rhs.jsonData.data(using: .utf8),
+                  let lhsJSONObject = try? JSONSerialization.jsonObject(with: lhsJSONData, options: []) as? NSObject,
+                  let rhsJSONObject = try? JSONSerialization.jsonObject(with: rhsJSONData, options: []) as? NSObject,
+                  lhsJSONObject == rhsJSONObject
+            else { return false }
+        }
+
+        return lhs.id == rhs.id &&
+        lhs.component == rhs.component &&
+        lhs.event == rhs.event &&
+        lhs.metadata == rhs.metadata
+    }
+}