[sequences] bugfix current child setting whilst moving through childr…

…en (#304)

py_trees/composites.py

@@ -423,6 +423,7 @@ def tick(self):
             try:
                 # advance if there is 'next' sibling
                 self.current_child = self.children[index + 1]
+                index += 1
             except IndexError:
                 pass
 

tests/test_sequences.py

@@ -39,6 +39,52 @@ def assert_details(text, expected, result):
 ##############################################################################
 
 
+def test_static_sequence_successes():
+    console.banner('Static Sequence Successes')
+    assert_banner()
+
+    success1 = py_trees.behaviours.Success(name="Success1")
+    success2 = py_trees.behaviours.Success(name="Success2")
+    success3 = py_trees.behaviours.Success(name="Success3")
+    success4 = py_trees.behaviours.Success(name="Success4")
+
+    children = [
+        success1,
+        success2,
+        success3,
+        success4,
+    ]
+    root = py_trees.composites.Sequence(name="Sequence", children=children)
+
+    root.tick_once()
+
+    assert_details("Current Child", success4.name, root.current_child.name)
+    assert root.tip().name == success4.name, 'should execute all 4 nodes of this Sequence'
+
+
+def test_static_sequence_with_failure():
+    console.banner('Static Sequence With Failure')
+    assert_banner()
+
+    success1 = py_trees.behaviours.Success(name="Success1")
+    success2 = py_trees.behaviours.Success(name="Success2")
+    failure = py_trees.behaviours.Failure(name="Failure")
+    success3 = py_trees.behaviours.Success(name="Success3")
+
+    children = [
+        success1,
+        success2,
+        failure,
+        success3,
+    ]
+    root = py_trees.composites.Sequence(name="Sequence", children=children)
+
+    root.tick_once()
+
+    assert_details("Current Child", failure.name, root.current_child.name)
+    assert root.tip().name == failure.name, 'should execute first 2 nodes of this Sequence and fail'
+
+
 def test_tick_add_with_current_child():
     console.banner('Tick-Add with Current Child')
     assert_banner()