From 9bec0ef8883c37d9871229df68035615f65ad6a4 Mon Sep 17 00:00:00 2001
From: Stefan van der Walt <stefan@sun.ac.za>
Date: Sat, 31 Oct 2009 21:10:27 +0200
Subject: [PATCH 1/5] Plugin framework for image I/O.

---
 scikits/image/io/__init__.py          |   6 +-
 scikits/image/io/io.py                | 107 ++++++++++++++++++++++++++
 scikits/image/io/matplotlib_plugin.py |   8 ++
 scikits/image/io/pil_imread.py        |  39 ----------
 scikits/image/io/pil_plugin.py        |  23 ++++++
 scikits/image/io/plugin.py            |  37 +++++++++
 6 files changed, 179 insertions(+), 41 deletions(-)
 create mode 100644 scikits/image/io/io.py
 create mode 100644 scikits/image/io/matplotlib_plugin.py
 delete mode 100644 scikits/image/io/pil_imread.py
 create mode 100644 scikits/image/io/pil_plugin.py
 create mode 100644 scikits/image/io/plugin.py

diff --git a/scikits/image/io/__init__.py b/scikits/image/io/__init__.py
index 3ef9e1e1..3107025f 100644
--- a/scikits/image/io/__init__.py
+++ b/scikits/image/io/__init__.py
@@ -1,7 +1,9 @@
 """Utilities to read and write images in various formats."""
 
+import pil_plugin
+import matplotlib_plugin
 
-from pil_imread import *
+from io import *
+from plugin import register as register_plugin
 from sift import *
 from collection import *
-
diff --git a/scikits/image/io/io.py b/scikits/image/io/io.py
new file mode 100644
index 00000000..e5a86a6f
--- /dev/null
+++ b/scikits/image/io/io.py
@@ -0,0 +1,107 @@
+from scikits.image.io.plugin import plugin_store
+
+def _call_plugin(kind, *args, **kwargs):
+    if not kind in plugin_store:
+        raise ValueError('Invalid function (%s) requested.' % kind)
+
+    plugin_funcs = plugin_store[kind]
+    if len(plugin_funcs) == 0:
+        raise RuntimeError('No suitable plugin registered for %s' % kind)
+
+    plugin = kwargs.pop('plugin', None)
+    if plugin is None:
+        _, func = plugin_funcs[0]
+    else:
+        try:
+            func = [f for (p,f) in plugin_funcs if p == plugin][0]
+        except IndexError:
+            raise RuntimeError('Could not find the plugin "%s" for %s.' % \
+                               (plugin, kind))
+
+    return func(*args, **kwargs)
+
+def imread(fname, as_grey=False, dtype=None, plugin=None, flatten=None,
+           **plugin_args):
+    """Load an image from file.
+
+    Parameters
+    ----------
+    fname : string
+        Image file name, e.g. ``test.jpg``.
+    as_grey : bool
+        If True, convert color images to grey-scale. If `dtype` is not given,
+        converted color images are returned as 32-bit float images.
+        Images that are already in grey-scale format are not converted.
+    dtype : dtype, optional
+        NumPy data-type specifier. If given, the returned image has this type.
+        If None (default), the data-type is determined automatically.
+    plugin : str
+        Name of plugin to use.  By default, the different plugins are
+        tried (starting with the Python Imaging Library) until a suitable
+        candidate is found.
+
+    Other Parameters
+    ----------------
+    flatten : bool
+        Backward compatible keyword, superseded by `as_grey`.
+
+    Returns
+    -------
+    img_array : ndarray
+        The different colour bands/channels are stored in the
+        third dimension, such that a grey-image is MxN, an
+        RGB-image MxNx3 and an RGBA-image MxNx4.
+
+    Other parameters
+    ----------------
+    plugin_args : keywords
+        Passed to the given plugin.
+
+    """
+    # Backward compatibility
+    if flatten is not None:
+        as_grey = flatten
+
+    _call_plugin('read', as_grey, dtype, plugin=plugin, **plugin_args)
+
+def imsave(fname, arr, plugin=None, **plugin_args):
+    """Save an image to file.
+
+    Parameters
+    ----------
+    fname : str
+        Target filename.
+    arr : ndarray of shape (M,N) or (M,N,3) or (M,N,4)
+        Image data.
+    plugin : str
+        Name of plugin to use.  By default, the different plugins are
+        tried (starting with the Python Imaging Library) until a suitable
+        candidate is found.
+
+    Other parameters
+    ----------------
+    plugin_args : keywords
+        Passed to the given plugin.
+
+    """
+    _call_plugin('save', fname, arr, plugin=plugin, **plugin_args)
+
+def imshow(arr, plugin=None, **plugin_args):
+    """Display an image.
+
+    Parameters
+    ----------
+    arr : ndarray
+        Image data.
+    plugin : str
+        Name of plugin to use.  By default, the different plugins are
+        tried (starting with the Python Imaging Library) until a suitable
+        candidate is found.
+
+    Other parameters
+    ----------------
+    plugin_args : keywords
+        Passed to the given plugin.
+
+    """
+    _call_plugin('show', arr, plugin=None, **plugin_args)
diff --git a/scikits/image/io/matplotlib_plugin.py b/scikits/image/io/matplotlib_plugin.py
new file mode 100644
index 00000000..3d748fe5
--- /dev/null
+++ b/scikits/image/io/matplotlib_plugin.py
@@ -0,0 +1,8 @@
+import plugin
+
+try:
+    import matplotlib.pyplot as plt
+except ImportError:
+    pass
+else:
+    plugin.register('matplotlib', show=plt.imshow, save=plt.imsave)
diff --git a/scikits/image/io/pil_imread.py b/scikits/image/io/pil_imread.py
deleted file mode 100644
index 421f45c7..00000000
--- a/scikits/image/io/pil_imread.py
+++ /dev/null
@@ -1,39 +0,0 @@
-__all__ = ['imread']
-
-import numpy as np
-
-def imread(fname, flatten=False, dtype=None):
-    """Load an image from file.
-
-    Parameters
-    ----------
-    fname : string
-        Image file name, e.g. ``test.jpg``.
-    flatten : bool
-        If True, convert color images to grey-scale. If `dtype` is not given,
-        converted color images are returned as 32-bit float images.
-        Images that are already in grey-scale format are not converted.
-    dtype : dtype, optional
-        NumPy data-type specifier. If given, the returned image has this type.
-        If None (default), the data-type is determined automatically.
-
-    Returns
-    -------
-    img_array : ndarray
-        The different colour bands/channels are stored in the
-        third dimension, such that a grey-image is MxN, an
-        RGB-image MxNx3 and an RGBA-image MxNx4.
-
-    """
-    try:
-        from PIL import Image
-    except ImportError:
-        raise ImportError("Could not import the Python Imaging Library (PIL)"
-                          " required to load image files.  Please refer to"
-                          " http://pypi.python.org/pypi/PIL/ for installation"
-                          " instructions.")
-
-    im = Image.open(fname)
-    if flatten and not im.mode in ('1', 'L', 'I', 'F', 'I;16', 'I;16L', 'I;16B'):
-        im = im.convert('F')
-    return np.array(im, dtype=dtype)
diff --git a/scikits/image/io/pil_plugin.py b/scikits/image/io/pil_plugin.py
new file mode 100644
index 00000000..2854baa3
--- /dev/null
+++ b/scikits/image/io/pil_plugin.py
@@ -0,0 +1,23 @@
+__all__ = ['imread']
+
+import numpy as np
+import plugin
+
+try:
+    from PIL import Image
+    has_pil = True
+except ImportError:
+    has_pil = False
+
+def imread(fname, as_grey=False, dtype=None):
+    """Load an image from file.
+
+    """
+    im = Image.open(fname)
+    if as_grey and \
+           not im.mode in ('1', 'L', 'I', 'F', 'I;16', 'I;16L', 'I;16B'):
+        im = im.convert('F')
+    return np.array(im, dtype=dtype)
+
+if has_pil:
+    plugin.register('PIL', read=imread)
diff --git a/scikits/image/io/plugin.py b/scikits/image/io/plugin.py
new file mode 100644
index 00000000..3557e2d8
--- /dev/null
+++ b/scikits/image/io/plugin.py
@@ -0,0 +1,37 @@
+"""Handle image reading, writing and plotting plugins.
+
+"""
+
+plugin_store = {'read': [],
+                'save': [],
+                'show': []}
+
+def register(name, **kwds):
+    """Register an image I/O plugin.
+
+    Parameters
+    ----------
+    name : str
+        Name of this plugin.
+    read : callable, optional
+        Function with signature
+        ``read(filename, as_grey=False, dtype=None, **plugin_specific_args)``
+        that reads images.
+    save : callable, optional
+        Function with signature
+        ``write(filename, arr, **plugin_specific_args)``
+        that writes an image to disk.
+    show : callable, optional
+        Function with signature
+        ``show(X, **plugin_specific_args)`` that displays an image.
+
+    """
+    for kind in kwds:
+        if kind not in plugin_store.keys():
+            raise ValueError('Tried to register invalid plugin method.')
+
+        func = kwds[kind]
+        if not callable(func):
+            raise ValueError('Can only register functions as plugins.')
+
+        plugin_store[kind].append((name, func))

From a7b17bb21b59c22a3fbcb3b2e6e9f111863ddb75 Mon Sep 17 00:00:00 2001
From: Stefan van der Walt <stefan@sun.ac.za>
Date: Sun, 1 Nov 2009 11:46:12 +0200
Subject: [PATCH 2/5] Add tests for IO plugins.

---
 scikits/image/io/__init__.py          |  3 +-
 scikits/image/io/io.py                | 10 +++++--
 scikits/image/io/tests/test_plugin.py | 40 +++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 4 deletions(-)
 create mode 100644 scikits/image/io/tests/test_plugin.py

diff --git a/scikits/image/io/__init__.py b/scikits/image/io/__init__.py
index 3107025f..3c701ff1 100644
--- a/scikits/image/io/__init__.py
+++ b/scikits/image/io/__init__.py
@@ -3,7 +3,8 @@
 import pil_plugin
 import matplotlib_plugin
 
-from io import *
 from plugin import register as register_plugin
 from sift import *
 from collection import *
+
+from io import *
diff --git a/scikits/image/io/io.py b/scikits/image/io/io.py
index e5a86a6f..2ad75532 100644
--- a/scikits/image/io/io.py
+++ b/scikits/image/io/io.py
@@ -1,3 +1,5 @@
+__all__ = ['imread', 'imsave', 'imshow']
+
 from scikits.image.io.plugin import plugin_store
 
 def _call_plugin(kind, *args, **kwargs):
@@ -20,6 +22,7 @@ def _call_plugin(kind, *args, **kwargs):
 
     return func(*args, **kwargs)
 
+
 def imread(fname, as_grey=False, dtype=None, plugin=None, flatten=None,
            **plugin_args):
     """Load an image from file.
@@ -62,7 +65,8 @@ def imread(fname, as_grey=False, dtype=None, plugin=None, flatten=None,
     if flatten is not None:
         as_grey = flatten
 
-    _call_plugin('read', as_grey, dtype, plugin=plugin, **plugin_args)
+    return _call_plugin('read', fname, as_grey=as_grey, dtype=dtype,
+                        plugin=plugin, **plugin_args)
 
 def imsave(fname, arr, plugin=None, **plugin_args):
     """Save an image to file.
@@ -84,7 +88,7 @@ def imsave(fname, arr, plugin=None, **plugin_args):
         Passed to the given plugin.
 
     """
-    _call_plugin('save', fname, arr, plugin=plugin, **plugin_args)
+    return _call_plugin('save', fname, arr, plugin=plugin, **plugin_args)
 
 def imshow(arr, plugin=None, **plugin_args):
     """Display an image.
@@ -104,4 +108,4 @@ def imshow(arr, plugin=None, **plugin_args):
         Passed to the given plugin.
 
     """
-    _call_plugin('show', arr, plugin=None, **plugin_args)
+    return _call_plugin('show', arr, plugin=plugin, **plugin_args)
diff --git a/scikits/image/io/tests/test_plugin.py b/scikits/image/io/tests/test_plugin.py
new file mode 100644
index 00000000..c39feeab
--- /dev/null
+++ b/scikits/image/io/tests/test_plugin.py
@@ -0,0 +1,40 @@
+from numpy.testing import *
+
+from scikits.image import io
+from scikits.image.io import plugin
+
+from copy import copy
+
+def read(fname, as_grey=False, dtype=None):
+    assert fname == 'test.png'
+    assert as_grey == True
+    assert dtype == 'i4'
+
+def save(fname, arr):
+    assert fname == 'test.png'
+    assert arr == [1, 2, 3]
+
+def show(arr, plugin_arg=None):
+    assert arr == [1, 2, 3]
+    assert plugin_arg == (1, 2)
+
+class TestPlugin:
+    def setup(self):
+        self.backup_plugin_store = copy(plugin.plugin_store)
+        plugin.register('test', read=read, save=save, show=show)
+
+    def test_read(self):
+        io.imread('test.png', as_grey=True, dtype='i4', plugin='test')
+
+    def test_save(self):
+        io.imsave('test.png', [1, 2, 3], plugin='test')
+
+    def test_show(self):
+        io.imshow([1, 2, 3], plugin_arg=(1, 2), plugin='test')
+
+    def teardown(self):
+        plugin.plugin_store = self.backup_plugin_store
+
+
+if __name__ == "__main__":
+    run_module_suite()

From cdb1a1560f9cecc00a5f509ca2f3deff15b19a2e Mon Sep 17 00:00:00 2001
From: Stefan van der Walt <stefan@sun.ac.za>
Date: Sun, 1 Nov 2009 11:56:21 +0200
Subject: [PATCH 3/5] Restore plugin registry after testing.

---
 scikits/image/io/tests/test_plugin.py | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/scikits/image/io/tests/test_plugin.py b/scikits/image/io/tests/test_plugin.py
index c39feeab..85ae7694 100644
--- a/scikits/image/io/tests/test_plugin.py
+++ b/scikits/image/io/tests/test_plugin.py
@@ -3,7 +3,7 @@ from numpy.testing import *
 from scikits.image import io
 from scikits.image.io import plugin
 
-from copy import copy
+from copy import deepcopy
 
 def read(fname, as_grey=False, dtype=None):
     assert fname == 'test.png'
@@ -18,11 +18,14 @@ def show(arr, plugin_arg=None):
     assert arr == [1, 2, 3]
     assert plugin_arg == (1, 2)
 
-class TestPlugin:
-    def setup(self):
-        self.backup_plugin_store = copy(plugin.plugin_store)
-        plugin.register('test', read=read, save=save, show=show)
+def setup_module(self):
+    self.backup_plugin_store = deepcopy(plugin.plugin_store)
+    plugin.register('test', read=read, save=save, show=show)
 
+def teardown_module(self):
+    plugin.plugin_store = self.backup_plugin_store
+
+class TestPlugin:
     def test_read(self):
         io.imread('test.png', as_grey=True, dtype='i4', plugin='test')
 
@@ -32,9 +35,5 @@ class TestPlugin:
     def test_show(self):
         io.imshow([1, 2, 3], plugin_arg=(1, 2), plugin='test')
 
-    def teardown(self):
-        plugin.plugin_store = self.backup_plugin_store
-
-
 if __name__ == "__main__":
     run_module_suite()

From e7d6875cab75f136c97c36eee7b546bb08d223f1 Mon Sep 17 00:00:00 2001
From: Stefan van der Walt <stefan@sun.ac.za>
Date: Sun, 1 Nov 2009 11:59:10 +0200
Subject: [PATCH 4/5] Document _call_plugin.

---
 scikits/image/io/io.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/scikits/image/io/io.py b/scikits/image/io/io.py
index 2ad75532..c4d61f99 100644
--- a/scikits/image/io/io.py
+++ b/scikits/image/io/io.py
@@ -3,6 +3,19 @@ __all__ = ['imread', 'imsave', 'imshow']
 from scikits.image.io.plugin import plugin_store
 
 def _call_plugin(kind, *args, **kwargs):
+    """Find the appropriate plugin of 'kind' and execute it.
+
+    Parameters
+    ----------
+    kind : {'imshow', 'imsave', 'imread'}
+        Function to look up.
+    plugin : str, optional
+        Plugin to load.  Defaults to None, in which case the first
+        matching plugin is used.
+    *args, **kwargs : arguments and keyword arguments
+        Passed to the plugin function.
+
+    """
     if not kind in plugin_store:
         raise ValueError('Invalid function (%s) requested.' % kind)
 

From 940f318b318c8e9f8c7e2bfd448ac5971c7dd9b1 Mon Sep 17 00:00:00 2001
From: Stefan van der Walt <stefan@sun.ac.za>
Date: Sun, 1 Nov 2009 12:38:36 +0200
Subject: [PATCH 5/5] Remove plugin functionality from io.py.  Implement
 setting default plugins and querying the plugins available.

---
 scikits/image/io/__init__.py          |   1 +
 scikits/image/io/io.py                |  42 +---------
 scikits/image/io/plugin.py            | 106 ++++++++++++++++++++++++++
 scikits/image/io/tests/test_plugin.py |  13 ++++
 4 files changed, 124 insertions(+), 38 deletions(-)

diff --git a/scikits/image/io/__init__.py b/scikits/image/io/__init__.py
index 3c701ff1..da516861 100644
--- a/scikits/image/io/__init__.py
+++ b/scikits/image/io/__init__.py
@@ -4,6 +4,7 @@ import pil_plugin
 import matplotlib_plugin
 
 from plugin import register as register_plugin
+
 from sift import *
 from collection import *
 
diff --git a/scikits/image/io/io.py b/scikits/image/io/io.py
index c4d61f99..11369bec 100644
--- a/scikits/image/io/io.py
+++ b/scikits/image/io/io.py
@@ -1,40 +1,6 @@
 __all__ = ['imread', 'imsave', 'imshow']
 
-from scikits.image.io.plugin import plugin_store
-
-def _call_plugin(kind, *args, **kwargs):
-    """Find the appropriate plugin of 'kind' and execute it.
-
-    Parameters
-    ----------
-    kind : {'imshow', 'imsave', 'imread'}
-        Function to look up.
-    plugin : str, optional
-        Plugin to load.  Defaults to None, in which case the first
-        matching plugin is used.
-    *args, **kwargs : arguments and keyword arguments
-        Passed to the plugin function.
-
-    """
-    if not kind in plugin_store:
-        raise ValueError('Invalid function (%s) requested.' % kind)
-
-    plugin_funcs = plugin_store[kind]
-    if len(plugin_funcs) == 0:
-        raise RuntimeError('No suitable plugin registered for %s' % kind)
-
-    plugin = kwargs.pop('plugin', None)
-    if plugin is None:
-        _, func = plugin_funcs[0]
-    else:
-        try:
-            func = [f for (p,f) in plugin_funcs if p == plugin][0]
-        except IndexError:
-            raise RuntimeError('Could not find the plugin "%s" for %s.' % \
-                               (plugin, kind))
-
-    return func(*args, **kwargs)
-
+from scikits.image.io import plugin as _plugin
 
 def imread(fname, as_grey=False, dtype=None, plugin=None, flatten=None,
            **plugin_args):
@@ -78,7 +44,7 @@ def imread(fname, as_grey=False, dtype=None, plugin=None, flatten=None,
     if flatten is not None:
         as_grey = flatten
 
-    return _call_plugin('read', fname, as_grey=as_grey, dtype=dtype,
+    return _plugin.call('read', fname, as_grey=as_grey, dtype=dtype,
                         plugin=plugin, **plugin_args)
 
 def imsave(fname, arr, plugin=None, **plugin_args):
@@ -101,7 +67,7 @@ def imsave(fname, arr, plugin=None, **plugin_args):
         Passed to the given plugin.
 
     """
-    return _call_plugin('save', fname, arr, plugin=plugin, **plugin_args)
+    return _plugin.call('save', fname, arr, plugin=plugin, **plugin_args)
 
 def imshow(arr, plugin=None, **plugin_args):
     """Display an image.
@@ -121,4 +87,4 @@ def imshow(arr, plugin=None, **plugin_args):
         Passed to the given plugin.
 
     """
-    return _call_plugin('show', arr, plugin=plugin, **plugin_args)
+    return _plugin.call('show', arr, plugin=plugin, **plugin_args)
diff --git a/scikits/image/io/plugin.py b/scikits/image/io/plugin.py
index 3557e2d8..42146bfc 100644
--- a/scikits/image/io/plugin.py
+++ b/scikits/image/io/plugin.py
@@ -2,6 +2,10 @@
 
 """
 
+__all__ = ['register', 'use']
+
+import warnings
+
 plugin_store = {'read': [],
                 'save': [],
                 'show': []}
@@ -35,3 +39,105 @@ def register(name, **kwds):
             raise ValueError('Can only register functions as plugins.')
 
         plugin_store[kind].append((name, func))
+
+
+def call(kind, *args, **kwargs):
+    """Find the appropriate plugin of 'kind' and execute it.
+
+    Parameters
+    ----------
+    kind : {'show', 'save', 'read'}
+        Function to look up.
+    plugin : str, optional
+        Plugin to load.  Defaults to None, in which case the first
+        matching plugin is used.
+    *args, **kwargs : arguments and keyword arguments
+        Passed to the plugin function.
+
+    """
+    if not kind in plugin_store:
+        raise ValueError('Invalid function (%s) requested.' % kind)
+
+    plugin_funcs = plugin_store[kind]
+    if len(plugin_funcs) == 0:
+        raise RuntimeError('No suitable plugin registered for %s' % kind)
+
+    plugin = kwargs.pop('plugin', None)
+    if plugin is None:
+        _, func = plugin_funcs[0]
+    else:
+        try:
+            func = [f for (p,f) in plugin_funcs if p == plugin][0]
+        except IndexError:
+            raise RuntimeError('Could not find the plugin "%s" for %s.' % \
+                               (plugin, kind))
+
+    return func(*args, **kwargs)
+
+def use(name, kind=None):
+    """Set the default plugin for a specified operation.
+
+    Parameters
+    ----------
+    name : str
+        Name of plugin.
+    kind : {'save', 'read', 'show'}, optional
+        Set the plugin for this function.  By default,
+        the plugin is set for all functions.
+
+    Examples
+    --------
+
+    Use Python Imaging Library to read images:
+
+    >>> from scikits.image.io import plugin
+    >>> plugin.use('PIL', 'read')
+
+    """
+    if kind is None:
+        kind = plugin_store.keys()
+    else:
+        kind = [kind]
+
+    for k in kind:
+        if not k in plugin_store:
+            raise RuntimeError("Could not find plugin for '%s'" % k)
+
+        funcs = plugin_store[k]
+
+        # Shuffle the plugins so that the requested plugin stands first
+        # in line
+        funcs = [(n, f) for (n, f) in funcs if n == name] + \
+                [(n, f) for (n, f) in funcs if n != name]
+
+        n, f = funcs[0]
+        if not n == name:
+            warnings.warn(RuntimeWarning('Could not set plugin "%s" for'
+                                         ' function "%s".' % (name, k)))
+
+        plugin_store[k] = funcs
+
+def available(kind=None):
+    """List available plugins.
+
+    Parameters
+    ----------
+    kind : {'show', 'save', 'read'}, optional
+        Display the plugin list for the given function type.  If not specified,
+        return a dictionary with the plugins for all functions.
+
+    """
+    if kind is None:
+        kind = plugin_store.keys()
+    else:
+        kind = [kind]
+
+    d = {}
+    for k in kind:
+        if not k in plugin_store:
+            raise ValueError('No function "%s" exists in the plugin registry.'
+                             % kind)
+
+        d[k] = [name for (name, func) in plugin_store[k]]
+
+    return d
diff --git a/scikits/image/io/tests/test_plugin.py b/scikits/image/io/tests/test_plugin.py
index 85ae7694..987ea8c7 100644
--- a/scikits/image/io/tests/test_plugin.py
+++ b/scikits/image/io/tests/test_plugin.py
@@ -18,9 +18,13 @@ def show(arr, plugin_arg=None):
     assert arr == [1, 2, 3]
     assert plugin_arg == (1, 2)
 
+def show_other(arr):
+    return "other"
+
 def setup_module(self):
     self.backup_plugin_store = deepcopy(plugin.plugin_store)
     plugin.register('test', read=read, save=save, show=show)
+    plugin.register('other', show=show_other)
 
 def teardown_module(self):
     plugin.plugin_store = self.backup_plugin_store
@@ -35,5 +39,14 @@ class TestPlugin:
     def test_show(self):
         io.imshow([1, 2, 3], plugin_arg=(1, 2), plugin='test')
 
+    def test_use(self):
+        plugin.use('other', 'show')
+        assert io.imshow(None) == 'other'
+
+    def test_available(self):
+        plugin.use('other', 'show')
+        d = plugin.available('show')
+        assert d['show'][0] == 'other'
+
 if __name__ == "__main__":
     run_module_suite()