diff --git a/qurro/_metadata_utils.py b/qurro/_metadata_utils.py
index 7dbe5c0b..15807569 100644
--- a/qurro/_metadata_utils.py
+++ b/qurro/_metadata_utils.py
@@ -137,6 +137,10 @@ def read_gnps_feature_metadata_file(md_file_loc, feature_ranks_df):
        with rows in the GNPS metadata file -- the precision of the numbers from
        which GNPS feature IDs are computed varies between the ranks/BIOM table
        and the actual numbers contained in the GNPS metadata file.
+
+       NOTE: this function is experimental and mostly untested. Things like
+       invalid inputs (e.g. non-numeric "parent mass" or "RTConsensus" values)
+       will cause problems.
     """
     # Note that we don't set index_col = 0 -- the columns we care about
     # ("parent mass", "RTConsensus", and "LibraryID"), as far as I know, don't
diff --git a/qurro/tests/test_metadata_utils.py b/qurro/tests/test_metadata_utils.py
index bd98c1e8..bc1b4021 100644
--- a/qurro/tests/test_metadata_utils.py
+++ b/qurro/tests/test_metadata_utils.py
@@ -5,7 +5,7 @@
 from pandas.errors import ParserError
 import qiime2
 from qurro._df_utils import replace_nan
-from qurro._metadata_utils import read_metadata_file
+from qurro._metadata_utils import read_metadata_file, get_truncated_feature_id
 
 
 def test_read_metadata_file_basic():
@@ -206,3 +206,27 @@ def test_read_metadata_file_nan_id():
 
     with pytest.raises(qiime2.metadata.MetadataFileError):
         qiime2.Metadata.load(ni)
+
+
+def test_get_truncated_feature_id():
+
+    ffi = "123.4567890123;456.7890123456789"
+    assert get_truncated_feature_id(ffi) == "123.4568;456.7890"
+
+    assert get_truncated_feature_id("1.2;3.4") == "1.2000;3.4000"
+
+    with pytest.raises(ValueError):
+        get_truncated_feature_id("")
+
+    with pytest.raises(ValueError):
+        get_truncated_feature_id(" ")
+
+    with pytest.raises(ValueError):
+        get_truncated_feature_id("abc")
+
+    with pytest.raises(ValueError):
+        get_truncated_feature_id("abc;def")
+
+    # Test case when there's too many semicolons
+    with pytest.raises(ValueError):
+        get_truncated_feature_id("1.0;2.0;3.0")