Fix ``test`` command possibly failing if an older version of the project

being tested was installed on ``sys.path`` ahead of the test source
directory.  (backport from trunk)

--HG--
branch : setuptools-0.6
extra : convert_revision : svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/sandbox/branches/setuptools-0.6%4053896

setuptools.txt

@@ -2622,6 +2622,10 @@ Release Notes/Change History
  * Fix ``#!`` parsing problems in Windows ``.exe`` script wrappers, when there
    was whitespace inside a quoted argument or at the end of the ``#!`` line
    (a regression introduced in 0.6c4).
+
+ * Fix ``test`` command possibly failing if an older version of the project
+   being tested was installed on ``sys.path`` ahead of the test source
+   directory.
  
 0.6c5
  * Fix uploaded ``bdist_rpm`` packages being described as ``bdist_egg``

setuptools/command/test.py

@@ -80,7 +80,7 @@ class test(Command):
 
 
 
-    def run(self):
+    def with_project_on_sys_path(self, func):
         # Ensure metadata is up-to-date
         self.run_command('egg_info')
 
@@ -88,7 +88,25 @@ class test(Command):
         self.reinitialize_command('build_ext', inplace=1)
         self.run_command('build_ext')
 
-        if self.distribution.tests_require:            
+        ei_cmd = self.get_finalized_command("egg_info")
+
+        old_path = sys.path[:]
+        old_modules = sys.modules.copy()
+
+        try:
+            sys.path.insert(0, normalize_path(ei_cmd.egg_base))
+            working_set.__init__()
+            require('%s==%s' % (ei_cmd.egg_name, ei_cmd.egg_version))
+            func()
+        finally:
+            sys.path[:] = old_path
+            sys.modules.clear()
+            sys.modules.update(old_modules)
+            working_set.__init__()
+
+
+    def run(self):
+        if self.distribution.tests_require:
             self.distribution.fetch_build_eggs(self.distribution.tests_require)
 
         if self.test_suite:
@@ -97,20 +115,14 @@ class test(Command):
                 self.announce('skipping "unittest %s" (dry run)' % cmd)
             else:
                 self.announce('running "unittest %s"' % cmd)
-                self.run_tests()
+                self.with_project_on_sys_path(self.run_tests)
+
+
+
 
 
     def run_tests(self):
         import unittest
-        old_path = sys.path[:]
-        ei_cmd = self.get_finalized_command("egg_info")
-        path_item = normalize_path(ei_cmd.egg_base)
-        metadata = PathMetadata(
-            path_item, normalize_path(ei_cmd.egg_info)
-        )
-        dist = Distribution(path_item, metadata, project_name=ei_cmd.egg_name)
-        working_set.add(dist)
-        require(str(dist.as_requirement()))
         loader_ep = EntryPoint.parse("x="+self.test_loader)
         loader_class = loader_ep.load(require=False)
         unittest.main(
@@ -121,3 +133,32 @@ class test(Command):
 
 
 
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