Add StepMixin

mentoring/step.py

+class StepParentMixin(object):
+    """
+    A parent containing the Step objects
+
+    The parent must have a get_children_objects() method.
+    """
+    @property
+    def steps(self):
+        return [child for child in self.get_children_objects() if isinstance(child, StepMixin)]
+
+
+class StepMixin(object):
+    @property
+    def step_number(self):
+        return self.parent.steps.index(self) + 1
+
+    @property
+    def lonely_step(self):
+        if self not in self.parent.steps:
+            raise ValueError("Step's parent should contain Step", self, self.parents.steps)
+        return len(self.parent.steps) == 1

test/unit/test_step.py

+import unittest
+
+from lxml import etree
+
+from mentoring import MentoringBlock
+import mentoring
+from mentoring.step import StepMixin, StepParentMixin
+
+class Parent(StepParentMixin):
+    def get_children_objects(self):
+        return list(self._children)
+
+    def _set_children_for_test(self, *children):
+        self._children = children
+        for child in self._children:
+            try:
+                child.parent = self
+            except AttributeError:
+                pass
+
+class Step(StepMixin):
+    def __init__(self): pass
+
+class NotAStep(object): pass
+
+class TestStepMixin(unittest.TestCase):
+    def test_single_step_is_returned_correctly(self):
+        block = Parent()
+        step = Step()
+        block._children = [step]
+
+        self.assertSequenceEqual(block.steps, [step])
+
+    def test_only_steps_are_returned(self):
+        block = Parent()
+        step1 = Step()
+        step2 = Step()
+        block._set_children_for_test(step1, 1, "2", "Step", NotAStep(), False, step2, NotAStep())
+
+        self.assertSequenceEqual(block.steps, [step1, step2])
+
+
+    def test_proper_number_is_returned_for_step(self):
+        block = Parent()
+        step1 = Step()
+        step2 = Step()
+        block._set_children_for_test(step1, 1, "2", "Step", NotAStep(), False, step2, NotAStep())
+
+        self.assertEquals(step1.step_number, 1)
+        self.assertEquals(step2.step_number, 2)
+
+    def test_the_number_does_not_represent_the_order_of_creation(self):
+        block = Parent()
+        step1 = Step()
+        step2 = Step()
+        block._set_children_for_test(step2, 1, "2", "Step", NotAStep(), False, step1, NotAStep())
+
+        self.assertEquals(step1.step_number, 2)
+        self.assertEquals(step2.step_number, 1)
+
+    def test_lonely_step_is_true_for_stand_alone_steps(self):
+        block = Parent()
+        step1 = Step()
+        block._set_children_for_test(1, "2", step1, "Step", NotAStep(), False)
+
+        self.assertTrue(step1.lonely_step)
+
+    def test_lonely_step_is_true_if_parent_have_more_steps(self):
+        block = Parent()
+        step1 = Step()
+        step2 = Step()
+        block._set_children_for_test(1, step2, "2", step1, "Step", NotAStep(), False)
+
+        self.assertFalse(step1.lonely_step)
+        self.assertFalse(step2.lonely_step)
+