def test_backend_with_guard():
"""Test that manipulating the stack with preserve_backend_stack() will
return the stack to its pristine state even i pushes and pops are
imbalanced.
"""
assert len(dtcwt._BACKEND_STACK) == 1
with dtcwt.preserve_backend_stack():
dtcwt.push_backend('numpy')
assert len(dtcwt._BACKEND_STACK) == 2
assert len(dtcwt._BACKEND_STACK) == 1
def test_backend_with_guard_and_exception():
"""Tests that even when preserving the backend stack, an exception is
correctly propagated.
"""
dtcwt.push_backend('numpy')
assert len(dtcwt._BACKEND_STACK) == 2
assert dtcwt.backend_name == 'numpy'
with raises(RuntimeError):
with dtcwt.preserve_backend_stack():
dtcwt.push_backend('opencl')
assert dtcwt.backend_name == 'opencl'
assert len(dtcwt._BACKEND_STACK) == 3
raise RuntimeError('test error')
assert dtcwt.backend_name == 'numpy'
assert len(dtcwt._BACKEND_STACK) == 2
def tst():
with dtcwt.preserve_backend_stack():
dtcwt.push_backend('numpy')
assert len(dtcwt._BACKEND_STACK) == 2
raise RuntimeError('test error')
