def test_vgroup_item_assignment_only_allows_vmobjects():
"""Test VGroup item-assignment raises TypeError when invalid type is passed"""
vgroup = VGroup(VMobject())
with pytest.raises(TypeError,
match="All submobjects must be of type VMobject"):
vgroup[0] = "invalid object"
def test_vmob_add_to_back():
"""Test the Mobject add_to_back method."""
a = VMobject()
b = Line()
c = "text"
with pytest.raises(ValueError):
# Mobject cannot contain self
a.add_to_back(a)
with pytest.raises(TypeError):
# All submobjects must be of type Mobject
a.add_to_back(c)
# No submobject gets added twice
a.add_to_back(b)
a.add_to_back(b, b)
assert len(a.submobjects) == 1
a.submobjects.clear()
a.add_to_back(b, b, b)
a.add_to_back(b, b)
assert len(a.submobjects) == 1
a.submobjects.clear()
# Make sure the ordering has not changed
o1, o2, o3 = Square(), Line(), Circle()
a.add_to_back(o1, o2, o3)
assert a.submobjects.pop() == o3
assert a.submobjects.pop() == o2
assert a.submobjects.pop() == o1