Add test extracting real data with no covariance

tests/metadata/test_metadata_two_point_sacc.py

@@ -955,3 +955,13 @@ def test_extract_all_data_harmonic_no_cov(sacc_galaxy_cells):
         match=("The SACC object does not have a dense covariance matrix."),
     ):
         _ = extract_all_harmonic_data(sacc_data, include_maybe_types=True)
+
+
+def test_extract_all_data_real_no_cov(sacc_galaxy_xis):
+    sacc_data, _, _ = sacc_galaxy_xis
+    sacc_data.covariance = None
+    with pytest.raises(
+        ValueError,
+        match=("The SACC object does not have a dense covariance matrix."),
+    ):
+        _ = extract_all_real_data(sacc_data, include_maybe_types=True)