Add test for sourcing bat file on windows

tests/batch.bat

@@ -0,0 +1,3 @@
+echo on
+set ENV_TO_BE_ADDED=Hallo world
+set ENV_TO_BE_REMOVED=

tests/test_foreign_shells.py

@@ -8,6 +8,7 @@ import nose
 from nose.plugins.skip import SkipTest
 from nose.tools import assert_equal, assert_true, assert_false
 
+from xonsh.tools import ON_WINDOWS
 from xonsh.foreign_shells import foreign_shell_data, parse_env, parse_aliases
 
 def test_parse_env():
@@ -54,5 +55,26 @@ def test_foreign_bash_data():
         yield assert_equal, expval, obsaliases.get(key, False)
 
 
+def test_foreign_cmd_data():
+    if not ON_WINDOWS:
+        raise SkipTest
+    env = (('ENV_TO_BE_REMOVED','test'),)
+    batchfile = os.path.join(os.path.dirname(__file__), 'batch.bat')
+    source_cmd ='call "{}"\necho off'.format(batchfile)
+    try:
+        obsenv, _ = foreign_shell_data('cmd',prevcmd=source_cmd, 
+                                        currenv=env,
+                                        interactive =False,
+                                        sourcer='call',envcmd='set',
+                                        use_tmpfile=True,
+                                        safe=False)
+    except (subprocess.CalledProcessError, FileNotFoundError):
+        raise SkipTest
+    
+    assert_true('ENV_TO_BE_ADDED' in obsenv) 
+    assert_true(obsenv['ENV_TO_BE_ADDED']=='Hallo world')
+    assert_true('ENV_TO_BE_REMOVED' not in obsenv)
+
+
 if __name__ == '__main__':
     nose.runmodule()