Add a simple xsh test file

tests/test_xonsh.xsh

@@ -1,19 +1,18 @@
 
 
-assert 1 + 1 == 2
+def test_simple():
+  assert 1 + 1 == 2
 
+  
+def test_envionment():
+  $USER = 'snail'
+  x = 'USER'
+  assert x in ${...}
+  assert ${'U' + 'SER'} == 'snail'
 
-$USER = 'snail'
-
-x = 'USER'
-assert x in ${...}
-assert ${'U' + 'SER'} == 'snail'
-
-
-echo "Yoo hoo"
-$(echo $USER)
-
-x = 'xonsh'
-y = 'party'
-out = $(echo @(x + ' ' + y))
-assert out == 'xonsh party\n'
+  
+def test_xonsh_party():
+  x = 'xonsh'
+  y = 'party'
+  out = $(echo @(x + ' ' + y))
+  assert out == 'xonsh party\n'