diff --git a/core/engine.py b/core/engine.py
index 4043e105..898a5082 100644
--- a/core/engine.py
+++ b/core/engine.py
@@ -223,7 +223,7 @@ def getmatches_by_contents(files, sizeattr='size', partial=False, j=job.nulljob)
         j.add_progress(desc=tr("%d matches found") % len(result))
     return result
 
-class Group(object):
+class Group:
     #---Override
     def __init__(self):
         self._clear()
diff --git a/core/gui/prioritize_dialog.py b/core/gui/prioritize_dialog.py
new file mode 100644
index 00000000..63287c81
--- /dev/null
+++ b/core/gui/prioritize_dialog.py
@@ -0,0 +1,30 @@
+# Created By: Virgil Dupras
+# Created On: 2011-09-06
+# Copyright 2011 Hardcoded Software (http://www.hardcoded.net)
+# 
+# This software is licensed under the "BSD" License as described in the "LICENSE" file, 
+# which should be included with this package. The terms are also available at 
+# http://www.hardcoded.net/licenses/bsd_license
+
+from hscommon.gui.selectable_list import SelectableList
+
+from ..prioritize import KindCategory
+
+class CriterionCategoryList(SelectableList):
+    def __init__(self, dialog):
+        self.dialog = dialog
+        SelectableList.__init__(self, [c.NAME for c in dialog.categories])
+    
+    def _update_selection(self):
+        self.dialog.select_category(self.dialog.categories[self.selected_index])
+
+
+class PrioritizeDialog:
+    def __init__(self, view, app):
+        self.categories = [KindCategory(app.results)]
+        self.category_list = CriterionCategoryList(self)
+        self.criteria_list = []
+    
+    def select_category(self, category):
+        criteria = category.criteria_list()
+        self.criteria_list = [c.value for c in criteria]
diff --git a/core/prioritize.py b/core/prioritize.py
new file mode 100644
index 00000000..a95b3898
--- /dev/null
+++ b/core/prioritize.py
@@ -0,0 +1,41 @@
+# Created By: Virgil Dupras
+# Created On: 2011/09/07
+# Copyright 2011 Hardcoded Software (http://www.hardcoded.net)
+# 
+# This software is licensed under the "BSD" License as described in the "LICENSE" file, 
+# which should be included with this package. The terms are also available at 
+# http://www.hardcoded.net/licenses/bsd_license
+
+from hscommon.util import dedupe, flatten
+
+class CriterionCategory:
+    NAME = "Undefined"
+    
+    def __init__(self, results):
+        self.results = results
+    
+    #--- Virtual
+    def _extract_value(self, dupe):
+        raise NotImplementedError()
+    
+    #--- Public
+    def criteria_list(self):
+        dupes = flatten(g[:] for g in self.results.groups)
+        values = dedupe(self._extract_value(d) for d in dupes)
+        return [Criterion(self, value) for value in values]
+
+class Criterion:
+    def __init__(self, category, value):
+        self.category = category
+        self.value = value
+    
+    @property
+    def display(self):
+        return "{} ({})".format(self.category, self.value)
+    
+
+class KindCategory(CriterionCategory):
+    NAME = "Kind"
+    
+    def _extract_value(self, dupe):
+        return dupe.extension
diff --git a/core/tests/app_test.py b/core/tests/app_test.py
index edb87dfa..3320fef7 100644
--- a/core/tests/app_test.py
+++ b/core/tests/app_test.py
@@ -16,36 +16,16 @@ from hscommon.path import Path
 import hscommon.conflict
 import hscommon.util
 from hscommon.testutil import CallLogger, eq_, log_calls
-from jobprogress.job import nulljob, Job, JobCancelled
+from jobprogress.job import Job
 
-from . import data
+from .base import DupeGuru
 from .results_test import GetTestGroups
 from .. import app, fs, engine
-from ..app import DupeGuru as DupeGuruBase
 from ..gui.details_panel import DetailsPanel
 from ..gui.directory_tree import DirectoryTree
 from ..gui.result_table import ResultTable
 from ..scanner import ScanType
 
-class DupeGuru(DupeGuruBase):
-    JOB = nulljob
-    
-    def __init__(self):
-        DupeGuruBase.__init__(self, data, '/tmp')
-    
-    def _start_job(self, jobid, func, *args):
-        try:
-            func(self.JOB, *args)
-        except JobCancelled:
-            return
-    
-    def _get_default(self, key_name):
-        return None
-    
-    def _set_default(self, key_name, value):
-        pass
-    
-
 def add_fake_files_to_directories(directories, files):
     directories.get_files = lambda j=None: iter(files)
     directories._dirs.append('this is just so Scan() doesnt return 3')
@@ -185,6 +165,7 @@ class TestCaseDupeGuru_clean_empty_dirs:
 
 class TestCaseDupeGuruWithResults:
     def pytest_funcarg__do_setup(self, request):
+        # XXX eventually, convert this to TestApp-based tests
         self.app = DupeGuru()
         self.objects,self.matches,self.groups = GetTestGroups()
         self.app.results.groups = self.groups
diff --git a/core/tests/base.py b/core/tests/base.py
new file mode 100644
index 00000000..87aaeec8
--- /dev/null
+++ b/core/tests/base.py
@@ -0,0 +1,103 @@
+# Created By: Virgil Dupras
+# Created On: 2011/09/07
+# Copyright 2011 Hardcoded Software (http://www.hardcoded.net)
+# 
+# This software is licensed under the "BSD" License as described in the "LICENSE" file, 
+# which should be included with this package. The terms are also available at 
+# http://www.hardcoded.net/licenses/bsd_license
+
+from hscommon.testutil import TestApp as TestAppBase, eq_, with_app
+from hscommon.path import Path
+from hscommon.util import get_file_ext
+from jobprogress.job import nulljob, JobCancelled
+
+from .. import engine
+from ..engine import getwords
+from ..app import DupeGuru as DupeGuruBase
+from ..gui.details_panel import DetailsPanel
+from ..gui.directory_tree import DirectoryTree
+from ..gui.result_table import ResultTable
+from ..gui.prioritize_dialog import PrioritizeDialog
+from . import data
+
+class DupeGuru(DupeGuruBase):
+    JOB = nulljob
+    
+    def __init__(self):
+        DupeGuruBase.__init__(self, data, '/tmp')
+    
+    def _start_job(self, jobid, func, *args):
+        try:
+            func(self.JOB, *args)
+        except JobCancelled:
+            return
+    
+    def _get_default(self, key_name):
+        return None
+    
+    def _set_default(self, key_name, value):
+        pass
+
+class NamedObject:
+    def __init__(self, name="foobar", with_words=False, size=1, folder=None):
+        self.name = name
+        if folder is None:
+            folder = Path('basepath')
+        self._folder = folder
+        self.size = size
+        self.md5partial = name
+        self.md5 = name
+        if with_words:
+            self.words = getwords(name)
+        self.is_ref = False
+    
+    def __bool__(self):
+        return False #Make sure that operations are made correctly when the bool value of files is false.
+    
+    @property
+    def path(self):
+        return self._folder + self.name
+    
+    @property
+    def folder_path(self):
+        return self.path[:-1]
+    
+    @property
+    def extension(self):
+        return get_file_ext(self.name)
+    
+# Returns a group set that looks like that:
+# "foo bar" (1)
+#   "bar bleh" (1024)
+#   "foo bleh" (1)
+# "ibabtu" (1)
+#   "ibabtu" (1)
+def GetTestGroups():
+    objects = [NamedObject("foo bar"),NamedObject("bar bleh"),NamedObject("foo bleh"),NamedObject("ibabtu"),NamedObject("ibabtu")]
+    objects[1].size = 1024
+    matches = engine.getmatches(objects) #we should have 5 matches
+    groups = engine.get_groups(matches) #We should have 2 groups
+    for g in groups:
+        g.prioritize(lambda x:objects.index(x)) #We want the dupes to be in the same order as the list is
+    groups.sort(key=len, reverse=True) # We want the group with 3 members to be first.
+    return (objects,matches,groups)
+
+class TestApp(TestAppBase):
+    def __init__(self):
+        make_gui = self.make_gui
+        self.app = DupeGuru()
+        # XXX After hscommon.testutil.TestApp has had its default parent changed to seomthing
+        # customizable (with adjustments in moneyguru) we can get rid of 'parent='
+        make_gui('rtable', ResultTable, parent=self.app)
+        make_gui('dtree', DirectoryTree, parent=self.app)
+        make_gui('dpanel', DetailsPanel, parent=self.app)
+        make_gui('pdialog', PrioritizeDialog, parent=self.app)
+        for elem in [self.rtable, self.dtree, self.dpanel]:
+            elem.connect()
+    
+    #--- Helpers
+    def select_pri_criterion(self, name):
+        # Select a main prioritize criterion by name instead of by index. Makes tests more
+        # maintainable.
+        index = self.pdialog.category_list.index(name)
+        self.pdialog.category_list.select(index)
diff --git a/core/tests/conftest.py b/core/tests/conftest.py
new file mode 100644
index 00000000..8115b8b1
--- /dev/null
+++ b/core/tests/conftest.py
@@ -0,0 +1 @@
+from hscommon.testutil import pytest_funcarg__app
\ No newline at end of file
diff --git a/core/tests/engine_test.py b/core/tests/engine_test.py
index d9bb7db5..acfaa62e 100644
--- a/core/tests/engine_test.py
+++ b/core/tests/engine_test.py
@@ -12,19 +12,10 @@ from jobprogress import job
 from hscommon.util import first
 from hscommon.testutil import eq_, log_calls
 
+from .base import NamedObject
 from .. import engine
 from ..engine import *
 
-class NamedObject:
-    def __init__(self, name="foobar", with_words=False, size=1):
-        self.name = name
-        self.size = size
-        self.md5partial = name
-        self.md5 = name
-        if with_words:
-            self.words = getwords(name)
-    
-
 no = NamedObject
 
 def get_match_triangle():
diff --git a/core/tests/prioritize_test.py b/core/tests/prioritize_test.py
new file mode 100644
index 00000000..41d4dc01
--- /dev/null
+++ b/core/tests/prioritize_test.py
@@ -0,0 +1,43 @@
+# Created By: Virgil Dupras
+# Created On: 2011/09/07
+# Copyright 2011 Hardcoded Software (http://www.hardcoded.net)
+# 
+# This software is licensed under the "BSD" License as described in the "LICENSE" file, 
+# which should be included with this package. The terms are also available at 
+# http://www.hardcoded.net/licenses/bsd_license
+
+from itertools import combinations
+
+from .base import TestApp, NamedObject, with_app, eq_
+from ..engine import Group, Match
+
+no = NamedObject
+
+def app_with_dupes(dupes):
+    # Creates an app with specified dupes. dupes is a list of lists, each list in the list being
+    # a dupe group. We cheat a little bit by creating dupe groups manually instead of running a
+    # dupe scan, but it simplifies the test code quite a bit
+    app = TestApp()
+    groups = []
+    for dupelist in dupes:
+        g = Group()
+        for dupe1, dupe2 in combinations(dupelist, 2):
+            g.add_match(Match(dupe1, dupe2, 100))
+        groups.append(g)
+    app.app.results.groups = groups
+    app.app._results_changed()
+    return app
+
+#---
+def app_normal_results():
+    # Just some results, with different extensions and size, for good measure.
+    dupes = [
+        [no('foo1.ext1', size=1), no('foo2.ext2', size=2)],
+    ]
+    return app_with_dupes(dupes)
+
+@with_app(app_normal_results)
+def test_kind_subcrit(app):
+    # The subcriteria of the "Kind" criteria is a list of extensions contained in the dupes.
+    app.select_pri_criterion("Kind")
+    eq_(app.pdialog.criteria_list, ['ext1', 'ext2'])
\ No newline at end of file
diff --git a/core/tests/results_test.py b/core/tests/results_test.py
index d726dbec..f611463b 100644
--- a/core/tests/results_test.py
+++ b/core/tests/results_test.py
@@ -1,6 +1,5 @@
 # Created By: Virgil Dupras
 # Created On: 2006/02/23
-# $Id$                                  
 # Copyright 2011 Hardcoded Software (http://www.hardcoded.net)
 # 
 # This software is licensed under the "BSD" License as described in the "LICENSE" file, 
@@ -12,42 +11,14 @@ import os.path as op
 
 from xml.etree import ElementTree as ET
 
-from hscommon.path import Path
 from hscommon.testutil import eq_
 from hscommon.util import first
 
-from . import engine_test, data
+from . import data
 from .. import engine
+from .base import NamedObject, GetTestGroups
 from ..results import Results
 
-class NamedObject(engine_test.NamedObject):
-    path = property(lambda x:Path('basepath') + x.name)
-    is_ref = False
-    
-    def __bool__(self):
-        return False #Make sure that operations are made correctly when the bool value of files is false.
-    
-    @property
-    def folder_path(self):
-        return self.path[:-1]
-    
-
-# Returns a group set that looks like that:
-# "foo bar" (1)
-#   "bar bleh" (1024)
-#   "foo bleh" (1)
-# "ibabtu" (1)
-#   "ibabtu" (1)
-def GetTestGroups():
-    objects = [NamedObject("foo bar"),NamedObject("bar bleh"),NamedObject("foo bleh"),NamedObject("ibabtu"),NamedObject("ibabtu")]
-    objects[1].size = 1024
-    matches = engine.getmatches(objects) #we should have 5 matches
-    groups = engine.get_groups(matches) #We should have 2 groups
-    for g in groups:
-        g.prioritize(lambda x:objects.index(x)) #We want the dupes to be in the same order as the list is
-    groups.sort(key=len, reverse=True) # We want the group with 3 members to be first.
-    return (objects,matches,groups)
-
 class TestCaseResultsEmpty:
     def setup_method(self, method):
         self.results = Results(data)