--- a
+++ b/tests/test_janggu_trim.py
@@ -0,0 +1,27 @@
+
+import os
+
+from pkg_resources import resource_filename
+
+from janggu.data import GenomicIndexer
+from janggu.janggutrim import trim_bed
+
+
+def test_create_from_array(tmpdir):
+    inbed = resource_filename('janggu', 'resources/bed_test.bed')
+
+    outbed = os.path.join(tmpdir.strpath, 'out.bed')
+    trim_bed(inbed, outbed, 5)
+
+    # original file
+    gindexer = GenomicIndexer.create_from_file(inbed, None, None)
+    reg = gindexer[0]
+    assert (reg.start % 5) == 0
+    assert (reg.end % 5) > 0
+
+    # trimmed file
+    gindexer = GenomicIndexer.create_from_file(outbed, None, None)
+    gindexer = GenomicIndexer.create_from_file(outbed, None, None)
+    reg = gindexer[0]
+    assert (reg.start % 5) == 0
+    assert (reg.end % 5) == 0