fix(findcode): better finding of test code

This fix sorts the --paths to look for code.
Longest paths come first. This is for cases where
one checks out other sources within his source directory.
In such a case this structure can happen:
my_package
my_package/src/some_other_package

Now when my_package gets found first. It logs an import
error and then goes on.
by sorting with longest paths first. I always get the most
specific match first. Since the loop is short circuited here,
it will never look at my_package.

This fixes #15

CHANGES.rst

@@ -4,7 +4,8 @@ zope.testrunner Changelog
 4.4.4 (unreleased)
 ==================
 
-- TBD
+- When looking for the right location of test code, start with longest
+  location paths first. This fixes problems with nested code locations.
 
 
 4.4.3 (2014-03-19)

src/zope/testrunner/find.py

@@ -171,8 +171,13 @@ def find_tests(options, found_suites=None):
 
 
 def find_suites(options):
+    # Sort prefixes so that longest prefixes come first.
+    # That is because only first match is evaluated which
+    # can be a problem with nested source packages.
+    sorted_prefixes = [x for x in options.prefix]
+    sorted_prefixes.sort(key=lambda prefix: len(prefix[0]), reverse=True)
     for fpath, package in find_test_files(options):
-        for (prefix, prefix_package) in options.prefix:
+        for (prefix, prefix_package) in sorted_prefixes:
             if fpath.startswith(prefix) and package == prefix_package:
                 # strip prefix, strip .py suffix and convert separator to dots
                 noprefix = fpath[len(prefix):]

src/zope/testrunner/tests/test_doctest.py

@@ -213,6 +213,7 @@ def test_suite():
         'testrunner-progress.txt',
         'testrunner-colors.txt',
         'testrunner-simple.txt',
+        'testrunner-nestedcode.txt',
         'testrunner-test-selection.txt',
         'testrunner-verbose.txt',
         'testrunner-repeat.txt',

src/zope/testrunner/tests/testrunner-discovery.txt

@@ -46,3 +46,26 @@ testrunner will exit with an error to prevent acidentally missing test cases:
       sample1.sampletests_discover_notests
     Total: 0 tests, 0 failures, 0 errors and 0 skipped in 0.000 seconds.
     True
+
+You can explicitly specify which tests to run by providing a function that
+returns a unittest.TestSuite in the test modules (the name of the function can
+be configured with the --suite-name parameter, it defaults to 'test_suite'). If
+no such function is present, testrunner will use all classes in the module that
+inherit from unittest.TestCase as tests:
+
+    >>> import os, sys
+    >>> directory_with_tests = os.path.join(this_directory, 'testrunner-ex')
+
+    >>> from zope import testrunner
+
+    >>> defaults = [
+    ...     ]
+    >>> sys.argv = ['test',
+    ...     ]
+    >>> testrunner.run(defaults)
+    Running zope.testrunner.layer.UnitTests tests:
+      Set up zope.testrunner.layer.UnitTests in N.NNN seconds.
+      Ran 2 tests with 0 failures, 0 errors and 0 skipped in N.NNN seconds.
+    Tearing down left over layers:
+      Tear down zope.testrunner.layer.UnitTests in N.NNN seconds.
+    False