diff --git a/src/jobflow_remote/testing/__init__.py b/src/jobflow_remote/testing/__init__.py
index e3d6362a..048e5005 100644
--- a/src/jobflow_remote/testing/__init__.py
+++ b/src/jobflow_remote/testing/__init__.py
@@ -43,16 +43,20 @@ def check_env_var() -> str:
     return os.environ.get("TESTING_ENV_VAR", "unset")
 
 
-@job(big_files="data")
+@job
 def add_big(a: float, b: float):
-    """Adds two numbers together and writes the answer to an artificially large file
-    which is stored in a pre-defined store."""
-    import pathlib
+    """Adds two numbers together and inflates the answer
+    to an array too large to store in MongoDB, then tries
+    to store that within the defined store.
+
+    """
+    import array
 
     result = a + b
-    with open("file.txt", "w") as f:
-        f.writelines([f"{result}"] * int(1e5))
-    return Response({"data": pathlib.Path("file.txt"), "result": a + b})
+    # create a 1.6 MB array that will be too large to store in MongoDB
+    # the array type "d" is a double-precision float, which is 8 bytes
+    big_array = array.array("d", [result] * 200_000)
+    return Response({"data": big_array, "result": a + b})
 
 
 @job(undefined_store="data")