Rewrite Export test so it doesn't pollute

test/builtin/files_io/test_importexport.py

@@ -8,6 +8,7 @@
 import pytest
 
 from mathics.builtin.atomic.strings import to_python_encoding
+from mathics.core.systemsymbols import SymbolFailed
 
 # def test_import():
 #     eaccent = "\xe9"
@@ -260,6 +261,16 @@ def test_private_doctests_importexport(str_expr, msgs, str_expected, fail_msg):
     )
 
 
+def test_inividually():
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".jcp") as tmp:
+        filename = osp.join(tmp.name, "123.jcp")
+        expr = f'Export["{filename}", 1+x,' + "{}]"
+        result = evaluate(expr)
+        outs = [out.text for out in session.evaluation.out]
+        assert result == SymbolFailed
+        assert outs == [f"Cannot infer format of file {filename}."]
+
+
 # TODO:
 # mmatera: please put in pytest conditionally
 # >> System`Convert`B64Dump`B64Encode["∫ f  x"]