revert importing test module behaviour to prepend by default

CHANGELOG

@@ -105,18 +105,18 @@
 
 - fix issue735: assertion failures on debug versions of Python 3.4+
 
-- change test module importing behaviour to append to sys.path
-  instead of prepending.  This better allows to run test modules
-  against installated versions of a package even if the package
-  under test has the same import root.  In this example::
+- new option ``--import-mode`` to allow to change test module importing 
+  behaviour to append to sys.path instead of prepending.  This better allows 
+  to run test modules against installated versions of a package even if the 
+  package under test has the same import root.  In this example::
 
         testing/__init__.py
         testing/test_pkg_under_test.py
         pkg_under_test/
 
-  the tests will preferrably run against the installed version
-  of pkg_under_test whereas before they would always pick
-  up the local version.  Thanks Holger Krekel.
+  the tests will run against the installed version
+  of pkg_under_test when ``--import-mode=append`` is used whereas 
+  by default they would always pick up the local version.  Thanks Holger Krekel.
 
 - pytester: add method ``TmpTestdir.delete_loaded_modules()``, and call it
   from ``inline_run()`` to allow temporary modules to be reloaded.

_pytest/__init__.py

@@ -1,2 +1,4 @@
-#
-__version__ = '2.8.0.dev5'
+# coding: utf-8
+# file generated by setuptools_scm
+# don't change, don't track in version control
+version = '2.7.4.dev394+ng2575053.d20150916'

_pytest/python.py

@@ -173,6 +173,12 @@ def pytest_addoption(parser):
         help="prefixes or glob names for Python test function and "
              "method discovery")
 
+    group.addoption("--import-mode", default="prepend",
+        choices=["prepend", "append"], dest="importmode",
+        help="prepend/append to sys.path when importing test modules, "
+             "default is to prepend.")
+
+
 def pytest_cmdline_main(config):
     if config.option.showfixtures:
         showfixtures(config)
@@ -557,8 +563,9 @@ class Module(pytest.File, PyCollector):
 
     def _importtestmodule(self):
         # we assume we are only called once per module
+        importmode = self.config.getoption("--import-mode")
         try:
-            mod = self.fspath.pyimport(ensuresyspath="append")
+            mod = self.fspath.pyimport(ensuresyspath=importmode)
         except SyntaxError:
             raise self.CollectError(
                 py.code.ExceptionInfo().getrepr(style="short"))

testing/python/collect.py

@@ -27,7 +27,7 @@ class TestModule:
             "*HINT*",
         ])
 
-    def test_import_appends_for_import(self, testdir, monkeypatch):
+    def test_import_prepend_append(self, testdir, monkeypatch):
         syspath = list(sys.path)
         monkeypatch.setattr(sys, "path", syspath)
         root1 = testdir.mkdir("root1")
@@ -35,13 +35,15 @@ class TestModule:
         root1.ensure("x456.py")
         root2.ensure("x456.py")
         p = root2.join("test_x456.py")
+        monkeypatch.syspath_prepend(str(root1))
         p.write(dedent("""\
             import x456
             def test():
                 assert x456.__file__.startswith(%r)
-        """ % str(root1)))
-        syspath.insert(0, str(root1))
+        """ % str(root2)))
         with root2.as_cwd():
+            reprec = testdir.inline_run("--import-mode=append")
+            reprec.assertoutcome(passed=0, failed=1)
             reprec = testdir.inline_run()
             reprec.assertoutcome(passed=1)