TEST: Test double collapse

Author: effigies

nipype/pipeline/engine/tests/test_nodes.py

@@ -290,3 +290,18 @@ def test_inputs_removal(tmpdir):
     n1.overwrite = True
     n1.run()
     assert not tmpdir.join(n1.name, 'file1.txt').check()
+
+
+def test_outputmultipath_collapse(tmpdir):
+    """Test an OutputMultiPath whose initial value is ``[[x]]`` to ensure that
+    it is returned as ``[x]``, regardless of how accessed."""
+    select_if = niu.Select(inlist=[[1, 2, 3], [4]], index=1)
+    select_nd = pe.Node(niu.Select(inlist=[[1, 2, 3], [4]], index=1),
+                        name='select_nd')
+
+    ifres = select_if.run()
+    ndres = select_nd.run()
+
+    assert ifres.outputs.out == [4]
+    assert ndres.outputs.out == [4]
+    assert select_nd.result.outputs.out == [4]