add test for 'bug' - only one sketch loaded from each sigfile

src/python/tests/test_gather.py

@@ -198,3 +198,27 @@ def test_bad_against_2(runtmp, capfd):
     print(captured.err)
 
     # @CTB: should be some kind of error message here.
+
+
+def test_against_multisigfile(runtmp):
+    # test against a sigfile that contains multiple sketches
+    query = get_test_data('SRR606249.sig.gz')
+    against_list = runtmp.output('against.txt')
+
+    sig2 = get_test_data('2.fa.sig.gz')
+    sig47 = get_test_data('47.fa.sig.gz')
+    sig63 = get_test_data('63.fa.sig.gz')
+
+    combined = runtmp.output('combined.sig.gz')
+    runtmp.sourmash('sig', 'cat', sig2, sig47, sig63, '-o', combined)
+    make_file_list(against_list, [combined])
+
+    g_output = runtmp.output('gather.csv')
+    p_output = runtmp.output('prefetch.csv')
+
+    runtmp.sourmash('scripts', 'fastgather', query, against_list,
+                    '-o', g_output, '--output-prefetch', p_output,
+                    '-s', '100000')
+    df = pandas.read_csv(g_output)
+    assert len(df) == 1
+    # @CTB this is a bug :(. It should load multiple sketches properly!