diff --git a/packages/pipeline/src/pyearthtools/pipeline/branching/branching.py b/packages/pipeline/src/pyearthtools/pipeline/branching/branching.py
index ea6a1af3..98502894 100644
--- a/packages/pipeline/src/pyearthtools/pipeline/branching/branching.py
+++ b/packages/pipeline/src/pyearthtools/pipeline/branching/branching.py
@@ -62,6 +62,13 @@ def expand_pipeline(original: PipelineBranchPoint, length: int) -> list[Pipeline
     return new_pipeline
 
 
+def _check_if_index(pipe: Pipeline):
+    """Check if pipeline is an index pipeline/branch"""
+    if isinstance(pipe.steps[0], PipelineBranchPoint):
+        return all(map(_check_if_index, pipe.steps[0].sub_pipelines))
+    return isinstance(pipe.steps[0], Index)
+
+
 class PipelineBranchPoint(_Pipeline, Operation):
     """
     Branch Point in a `Pipeline`.
@@ -154,7 +161,9 @@ def apply(self, sample):
                     raise PipelineRuntimeError(
                         f"Cannot map sample to branches as length differ. {len(sample)} != {len(self.sub_pipelines)}."
                     )
-                elif self._map_copy:
+                elif (
+                    self._map_copy
+                ):  # pragma: no cover # cannot be fully tested - if this line is reached, self._map_copy is True
                     self.sub_pipelines = expand_pipeline(self, len(sample))
 
             for s, pipe in zip(sample, self.sub_pipelines):
@@ -213,13 +222,7 @@ def undo(self, sample):
                 # )
             result = tuple(self.parallel_interface.collect(sub_samples))
 
-        def check_if_index(pipe: Pipeline):
-            """Check if pipeline is an index pipeline/branch"""
-            if isinstance(pipe.steps[0], PipelineBranchPoint):
-                return all(map(check_if_index, pipe.steps[0].sub_pipelines))
-            return isinstance(pipe.steps[0], Index)
-
-        if all(len(pipe.steps) == 1 or check_if_index(pipe) for pipe in self.sub_pipelines):
+        if all(len(pipe.steps) == 1 or _check_if_index(pipe) for pipe in self.sub_pipelines):
             if all(map(lambda x: result[0] == x, result[1:])):
                 return result[0]
         return result
diff --git a/packages/pipeline/tests/fake_pipeline_steps.py b/packages/pipeline/tests/fake_pipeline_steps.py
index 604885cb..b1e74c53 100644
--- a/packages/pipeline/tests/fake_pipeline_steps.py
+++ b/packages/pipeline/tests/fake_pipeline_steps.py
@@ -33,6 +33,9 @@ def __init__(self, override: int | None = None):
     def get(self, idx):
         return self._overrideValue or idx
 
+    def __eq__(self, other):
+        return type(other) is FakeIndex and other._overrideValue == self._overrideValue
+
 
 class MultiplicationOperation(Operation):
     def __init__(self, factor):
diff --git a/packages/pipeline/tests/test_controller/test_branchpoints.py b/packages/pipeline/tests/test_controller/test_branchpoints.py
index 8898fc61..c99cbd54 100644
--- a/packages/pipeline/tests/test_controller/test_branchpoints.py
+++ b/packages/pipeline/tests/test_controller/test_branchpoints.py
@@ -19,6 +19,7 @@
 import pyearthtools.utils
 
 from pyearthtools.pipeline import Pipeline, exceptions, branching
+from pyearthtools.pipeline.warnings import PipelineWarning
 
 from tests.fake_pipeline_steps import FakeIndex, MultiplicationOperation, MultiplicationOperationUnunifiedable
 
@@ -28,6 +29,7 @@
 def test_branchingpoint_basic():
     pipe = Pipeline((FakeIndex(), FakeIndex()))
     assert pipe[1] == (1, 1)
+    assert pipe.complete_steps == (((FakeIndex(),), (FakeIndex(),)),)
 
 
 def test_branch_differing_operations():
@@ -87,6 +89,8 @@ def test_branch_differing_operations_nested_larger():
 def test_branch_differing_operations_undo():
     pipe = Pipeline(FakeIndex(), (MultiplicationOperation(10), MultiplicationOperation(2)))
     assert pipe.undo(pipe[1]) == 1
+    with pytest.warns(PipelineWarning):
+        pipe._steps[1].undo((30, 20, 10))
 
 
 # def test_branch_differing_operations_undo_unify():
@@ -168,6 +172,8 @@ def test_branch_with_mapping_copy():
         (MultiplicationOperation(1), "map_copy"),
     )
     assert pipe[1] == (1, 2)
+    # test round robin application of undo
+    assert pipe._steps[1].undo((30, 20, 10)) == (30, 20, 10)
 
 
 def test_branch_with_mapping_not_tuple():
@@ -199,3 +205,48 @@ def test_branch_with_source():
         (MultiplicationOperation(2), FakeIndex()),
     )
     assert pipe[1] == (2, 1)
+
+    # test error when trying to map to a datasource
+    pipe = Pipeline((FakeIndex(1),), (FakeIndex(2), "map"))
+    with pytest.raises(ValueError):
+        pipe[0]
+
+    # test branching with None index
+    pipe = Pipeline((FakeIndex(1),), (FakeIndex(2),))
+    with pytest.raises(ValueError):
+        pipe[None]
+
+
+def test_check_index():
+    pipe = Pipeline(
+        (MultiplicationOperation(2), MultiplicationOperation(3)),
+    )
+    assert not branching.branching._check_if_index(pipe)
+
+
+def test_nested_branching_undo_nosource():
+    pipe = Pipeline(
+        (
+            (
+                MultiplicationOperation(2),
+                MultiplicationOperation(3),
+            ),
+            MultiplicationOperation(4),
+        )
+    )
+    assert pipe.undo((18, 8)) == (3, 2)
+
+
+def test_expand_pipeline_skip_non_pipeline():
+    """Tests that expand_pipeline function ignore non-pipeline objects."""
+
+    # instantiate pipline with branchpoint at step 0.
+    pipe = Pipeline(
+        (MultiplicationOperation(3), MultiplicationOperation(4)),
+    )
+
+    # add the non-pipeline object to branchpoint sub pipelines
+    pipe._steps[0].sub_pipelines.append((1,))
+
+    # test that the non pipeline object isn't in the resultant expanded pipeline.
+    assert (1,) not in branching.branching.expand_pipeline(pipe._steps[0], 3)