def test_negative_label_doesnt_flicker():
data = np.array([
[[0, 5], [0, 5]],
[[-1, 5], [-1, 5]],
[[-1, 6], [-1, 6]],
])
layer = Labels(data)
layer._dims_point = (1, 0, 0)
layer._set_view_slice()
# this is expected to fail: -1 doesn't trigger an index error in
# layer._all_vals, it instead just wraps to 5, the previous max label.
assert tuple(layer.get_color(-1)) != tuple(layer.get_color(5))
minus_one_color_original = tuple(layer.get_color(-1))
layer.dims_point = (2, 0, 0)
layer._set_view_slice()
# this is also expected to fail: when we switch layers, we see the 6
# label, which causes an index error, which triggers a recalculation of
# the label colors. Now -1 is seen so it is taken into account in the
# indexing calculation, and changes color
assert tuple(layer.get_color(-1)) == minus_one_color_original
