Created a test for downloading the core with the core.

added some safe checks in the core

core.lua

@@ -98,8 +98,17 @@ function Core:download(file)
         return false, "Invalid type: "..textutils.serialiseJSON(data)
     end
 
+    if fs.exists(file) then
+        fs.delete(file);
+    end
+
     local fileStream = io.open(file, "w");
-    fileStream:write(data.fileContent);
+
+    if not fileStream then
+        return false, "Failed to open fileStream"
+    end
+
+    fileStream:write(data.data);
     fileStream:close();
 
     return true, "Success"

downloadCore.lua

@@ -0,0 +1,9 @@
+require("core")
+
+local core = Core.new();
+
+core:connect();
+
+core:download("core.lua");
+
+core:disconnect();