test: add snapshot tests for MessageBuilder (#5598)

mocks/include/mocks/UserData.hpp

@@ -2,6 +2,8 @@
 
 #include "controllers/userdata/UserDataController.hpp"
 
+#include <unordered_map>
+
 namespace chatterino::mock {
 
 class UserDataController : public IUserDataController
@@ -13,6 +15,11 @@ public:
     // If the user does not have any extra data, return none
     std::optional<UserData> getUser(const QString &userID) const override
     {
+        auto it = this->userMap.find(userID);
+        if (it != this->userMap.end())
+        {
+            return it->second;
+        }
         return std::nullopt;
     }
 
@@ -20,8 +27,21 @@ public:
     void setUserColor(const QString &userID,
                       const QString &colorString) override
     {
-        // do nothing
+        auto it = this->userMap.find(userID);
+        if (it != this->userMap.end())
+        {
+            it->second.color = QColor(colorString);
+        }
+        else
+        {
+            this->userMap.emplace(userID, UserData{
+                                              .color = QColor(colorString),
+                                          });
+        }
     }
+
+private:
+    std::unordered_map<QString, UserData> userMap;
 };
 
 }  // namespace chatterino::mock