unit-test for unprintable(). last unit-test todo.

TODO

@@ -11,8 +11,6 @@ NOW: Should probably do before it hits users
    * conflict error message
    * all requirements already satisfied -> "must specify at least one requirement" error
 
-* resolve all the todo:unit-test notes
-
 
 LATER: Things that I want to do, but would put me past my deadline:
 ------------------------------------------------------------

tests/functional/simple_test.py

@@ -265,7 +265,6 @@ def pipe_output(read, write):
 
 def unprintable(mystring):
     """return only the unprintable characters of a string"""
-    # TODO: unit-test
     from string import printable
     return ''.join(
         character

tests/unit/simple_test.py

@@ -255,3 +255,16 @@ def fakewait():
 
     assert _nonlocal.wait == 0
     assert _nonlocal.thrown is True
+
+
+def test_unprintable():
+    from functional.simple_test import unprintable
+    import string
+    assert unprintable(string.printable) == ''
+
+    _ascii = ''.join(chr(i) for i in range(0x80))
+    assert unprintable(_ascii) == (
+        '\x00\x01\x02\x03\x04\x05\x06\x07\x08\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x7f'
+    )
+
+    assert set(_ascii) - set(unprintable(_ascii)) == set(string.printable)