[python-dtcwt] 389/497: add testcase for switchable backends

[Ghislain Vaillant]

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ghisvail-guest pushed a commit to branch debian/sid
in repository python-dtcwt.

commit 1cee24c4da523cd75a79ff1ab6917c6e9d04a4d3
Author: Rich Wareham <rjw57 at cam.ac.uk>
Date:   Mon Feb 10 14:50:39 2014 +0000

    add testcase for switchable backends
    
    Add test cases which define the expected behaviour for switchable
    backends.
---
 tests/testswitchbackends.py | 90 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)

diff --git a/tests/testswitchbackends.py b/tests/testswitchbackends.py
new file mode 100644
index 0000000..4e1841b
--- /dev/null
+++ b/tests/testswitchbackends.py
@@ -0,0 +1,90 @@
+import dtcwt
+import dtcwt.numpy as npbackend
+import dtcwt.opencl as clbackend
+
+from unittest import TestCase
+from nose.tools import raises, assert_raises
+from .util import skip_if_no_cl
+
+class TestSwitchBackends(TestCase):
+    def __init__(self, *args, **kwargs):
+        super(TestSwitchBackends, self).__init__(*args, **kwargs)
+        self._orig_stack = None
+
+    def setUp(self):
+        # Preserve _BACKEND_STACK in case test fails. This stops one test
+        # failure messing up other tests. This requires knowledge of how dtcw
+        # manages the backend stack which is not part of the public API.
+        #
+        # Perhaps we need to add __enter__() and __exit__() functions to a
+        # stack object.
+        self._orig_stack = list(dtcwt._BACKEND_STACK)
+
+    def tearDown(self):
+        dtcwt._BACKEND_STACK = self._orig_stack
+
+    def test_default_backend(self):
+        assert dtcwt.Transform2d is npbackend.Transform2d
+        assert dtcwt.Pyramid is npbackend.Pyramid
+        assert dtcwt.backend_name == 'numpy'
+
+    @skip_if_no_cl
+    def test_switch_to_opencl(self):
+        assert dtcwt.Transform2d is npbackend.Transform2d
+        assert dtcwt.Pyramid is npbackend.Pyramid
+        assert dtcwt.backend_name == 'numpy'
+        dtcwt.push_backend('opencl')
+        assert dtcwt.Transform2d is clbackend.Transform2d
+        assert dtcwt.Pyramid is clbackend.Pyramid
+        assert dtcwt.backend_name == 'opencl'
+        dtcwt.pop_backend()
+        assert dtcwt.Transform2d is npbackend.Transform2d
+        assert dtcwt.Pyramid is npbackend.Pyramid
+        assert dtcwt.backend_name == 'numpy'
+
+    def test_switch_to_numpy(self):
+        assert dtcwt.Transform2d is npbackend.Transform2d
+        assert dtcwt.Pyramid is npbackend.Pyramid
+        assert dtcwt.backend_name == 'numpy'
+        dtcwt.push_backend('numpy')
+        assert dtcwt.Transform2d is npbackend.Transform2d
+        assert dtcwt.Pyramid is npbackend.Pyramid
+        assert dtcwt.backend_name == 'numpy'
+        dtcwt.pop_backend()
+        assert dtcwt.Transform2d is npbackend.Transform2d
+        assert dtcwt.Pyramid is npbackend.Pyramid
+        assert dtcwt.backend_name == 'numpy'
+
+    @raises(ValueError)
+    def test_switch_to_invalid(self):
+        dtcwt.push_backend('does-not-exist')
+
+    @raises(IndexError)
+    def test_no_pop_default_backend(self):
+        dtcwt.pop_backend()
+
+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.
+
+    """
+    assert len(dtcwt._BACKEND_STACK) == 1
+    def tst():
+        with dtcwt.preserve_backend_stack():
+            dtcwt.push_backend('numpy')
+            assert len(dtcwt._BACKEND_STACK) == 2
+            raise RuntimeError('test error')
+    assert_raises(RuntimeError, tst)
+    assert len(dtcwt._BACKEND_STACK) == 1

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