diff --git a/whereto/app.py b/whereto/app.py
index b06e409..fef9636 100644
--- a/whereto/app.py
+++ b/whereto/app.py
@@ -15,18 +15,74 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+from __future__ import print_function
+
 import argparse
+import io
+
+from whereto import parser
+from whereto import rules
+
+
+def process_tests(ruleset, tests):
+    """Run the tests against the ruleset and return the results.
+
+    Results are generated as tuples containing the inputs that did not
+    match the expected value. The first element is the test tuple
+    (line, input, expected), and the second element is the list of any
+    rules that did match the input pattern.
+
+    :param ruleset: The redirect rules.
+    :type ruleset: RuleSet
+
+    """
+    for linenum, input, code, expected in tests:
+        matches = list(ruleset.match(input))
+        if len(matches) == 1:
+            match = matches[0]
+            if (code, expected) == match[1:]:
+                continue
+        yield ((linenum, input, code, expected), matches)
 
 
 def main():
-    parser = argparse.ArgumentParser()
-    parser.add_argument(
+    arg_parser = argparse.ArgumentParser()
+    arg_parser.add_argument(
         'htaccess_file',
         help='file with rewrite rules',
     )
-    parser.add_argument(
+    arg_parser.add_argument(
         'test_file',
         help='file with test data',
     )
-    args = parser.parse_args()
-    print(args)
+    args = arg_parser.parse_args()
+
+    ruleset = rules.RuleSet()
+    with io.open(args.htaccess_file, 'r', encoding='utf-8') as f:
+        for linenum, params in parser.parse_rules(f):
+            ruleset.add(linenum, *params)
+
+    with io.open(args.test_file, 'r', encoding='utf-8') as f:
+        tests = [
+            (linenum,) + tuple(params)
+            for linenum, params in parser.parse_rules(f)
+        ]
+
+    failures = 0
+    for test, matches in process_tests(ruleset, tests):
+        failures += 1
+        if not matches:
+            print('No rule matched test on line {}: {}'.format(
+                test[0], ' '.join(test[1:]))
+            )
+        else:
+            print('Test on line {} did not produce expected result: {}'.format(
+                test[0], ' '.join(test[1:]))
+            )
+            for match in matches:
+                print('  {}'.format(ruleset[match[0]]))
+
+    if failures:
+        print('\n{} failures'.format(failures))
+        return 1
+    return 0
diff --git a/whereto/rules.py b/whereto/rules.py
index 366c310..9ed3603 100644
--- a/whereto/rules.py
+++ b/whereto/rules.py
@@ -82,11 +82,16 @@ class RuleSet(object):
 
     def __init__(self):
         self._rules = []
+        self._by_num = {}
 
     def add(self, linenum, *params):
         rule_type = params[0].lower()
         rule = self._factories[rule_type](linenum, *params)
         self._rules.append(rule)
+        self._by_num[linenum] = rule
+
+    def __getitem__(self, index):
+        return self._by_num[index]
 
     def __iter__(self):
         return iter(self._rules)
diff --git a/whereto/tests/test_app.py b/whereto/tests/test_app.py
new file mode 100644
index 0000000..48920af
--- /dev/null
+++ b/whereto/tests/test_app.py
@@ -0,0 +1,52 @@
+# -*- coding: utf-8 -*-
+
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from whereto import app
+from whereto import rules
+from whereto.tests import base
+
+
+class TestProcessTests(base.TestCase):
+
+    def setUp(self):
+        super(TestProcessTests, self).setUp()
+        self.ruleset = rules.RuleSet()
+        self.ruleset.add(
+            1,
+            'redirect', '301', '/path', '/new/path',
+        )
+
+    def test_one_match(self):
+        actual = list(app.process_tests(
+            self.ruleset,
+            [(1, '/path', '301', '/new/path')],
+        ))
+        expected = []
+        self.assertEqual(expected, actual)
+
+    def test_two_matches(self):
+        self.ruleset.add(
+            2,
+            'redirect', '301', '/path', '/duplicate/redirect',
+        )
+        actual = list(app.process_tests(
+            self.ruleset,
+            [(1, '/path', '301', '/new/path')],
+        ))
+        expected = [
+            ((1, '/path', '301', '/new/path'),
+             [(1, '301', '/new/path'),
+              (2, '301', '/duplicate/redirect')])
+        ]
+        self.assertEqual(expected, actual)