diff --git a/common/lib/capa/capa_problem.py b/common/lib/capa/capa_problem.py
index a817433b49..4b40df6653 100644
--- a/common/lib/capa/capa_problem.py
+++ b/common/lib/capa/capa_problem.py
@@ -12,6 +12,7 @@ import logging
 import math
 import numpy
 import os
+import os.path
 import random
 import re
 import scipy
@@ -125,6 +126,9 @@ class LoncapaProblem(object):
             responder = response_types[response.tag](response, self.context, self.system)
             responder.preprocess_response()
 
+    def __unicode__(self):
+        return u"LoncapaProblem ({0})".format(self.fileobject)
+
     def get_state(self):
         ''' Stored per-user session data neeeded to: 
             1) Recreate the problem
@@ -174,10 +178,11 @@ class LoncapaProblem(object):
         return self.correct_map
 
     def get_question_answers(self):
-        '''
-        Make a dict of (id,correct_answer) entries, for all the problems. 
-        Called by "show answers" button JSON request (see capa_module)
-        '''
+        """Returns a dict of answer_ids to answer values. If we can't generate
+        an answer (this sometimes happens in customresponses), that answer_id is 
+        not included. Called by "show answers" button JSON request 
+        (see capa_module)
+        """
         context=self.extract_context(self.tree)
         answer_map = dict()
         problems_simple = self.extract_problems(self.tree)	# purified (flat) XML tree of just response queries
@@ -201,6 +206,24 @@ class LoncapaProblem(object):
 
         return answer_map
 
+    def get_answer_ids(self):
+        """Return the IDs of all the responses -- these are the keys used for 
+        the dicts returned by grade_answers and get_question_answers. (Though 
+        get_question_answers may only return a subset of these."""
+        answer_ids = []
+        context=self.extract_context(self.tree)
+        problems_simple = self.extract_problems(self.tree)
+        for response in problems_simple:
+            responder = response_types[response.tag](response, self.context)
+            if hasattr(responder, "answer_id"):
+                answer_ids.append(responder.answer_id)
+            # customresponse types can have multiple answer_ids
+            elif hasattr(responder, "answer_ids"):
+                answer_ids.extend(responder.answer_ids)
+
+        return answer_ids
+
+
     # ======= Private ========
 
     def extract_context(self, tree, seed = struct.unpack('i', os.urandom(4))[0]):  # private
diff --git a/common/lib/capa/checker.py b/common/lib/capa/checker.py
new file mode 100755
index 0000000000..742d28766b
--- /dev/null
+++ b/common/lib/capa/checker.py
@@ -0,0 +1,159 @@
+#!/usr/bin/env python
+"""
+Commandline tool for doing operations on Problems
+"""
+from __future__ import unicode_literals
+
+import argparse
+import logging
+import sys
+from path import path
+
+from cStringIO import StringIO
+from collections import defaultdict
+
+from calc import UndefinedVariable
+from capa_problem import LoncapaProblem
+from mako.lookup import TemplateLookup
+
+logging.basicConfig(format="%(levelname)s %(message)s")
+log = logging.getLogger('capa.checker')
+
+
+class DemoSystem(object):
+    def __init__(self):
+        self.lookup = TemplateLookup(directories=[path(__file__).dirname() / 'templates'])
+
+    def render_template(self, template_filename, dictionary, context=None):
+        if context is None:
+            context = {}
+
+        context_dict = {}
+        context_dict.update(dictionary)
+        context_dict.update(context)
+        return self.lookup.get_template(template_filename).render(**context_dict)
+
+def main():
+    parser = argparse.ArgumentParser(description='Check Problem Files')
+    parser.add_argument("command", choices=['test', 'show']) # Watch? Render? Open?
+    parser.add_argument("files", nargs="+", type=argparse.FileType('r'))
+    parser.add_argument("--seed", required=False, type=int)
+    parser.add_argument("--log-level", required=False, default="INFO",
+                        choices=['info', 'debug', 'warn', 'error',
+                                 'INFO', 'DEBUG', 'WARN', 'ERROR'])
+
+    args = parser.parse_args()
+    log.setLevel(args.log_level.upper())
+
+    system = DemoSystem()
+
+    for problem_file in args.files:
+        log.info("Opening {0}".format(problem_file.name))
+
+        try:
+            problem = LoncapaProblem(problem_file, "fakeid", seed=args.seed, system=system)
+        except Exception as ex:
+            log.error("Could not parse file {0}".format(problem_file.name))
+            log.exception(ex)
+            continue
+
+        if args.command == 'test':
+            command_test(problem)
+        elif args.command == 'show':
+            command_show(problem)
+
+        problem_file.close()
+
+    # In case we want to do anything else here.
+
+def command_show(problem):
+    """Display the text for this problem"""
+    print problem.get_html()
+    
+
+def command_test(problem):
+    # We're going to trap stdout/stderr from the problems (yes, some print)    
+    old_stdout, old_stderr = sys.stdout, sys.stderr
+    try:
+        sys.stdout = StringIO()
+        sys.stderr = StringIO()
+
+        check_that_suggested_answers_work(problem)
+        check_that_blanks_fail(problem)
+
+        log_captured_output(sys.stdout, 
+                            "captured stdout from {0}".format(problem))
+        log_captured_output(sys.stderr,
+                            "captured stderr from {0}".format(problem))
+    except Exception as e:
+        log.exception(e)
+    finally:
+        sys.stdout, sys.stderr = old_stdout, old_stderr
+
+def check_that_blanks_fail(problem):
+    """Leaving it blank should never work. Neither should a space."""
+    blank_answers = dict((answer_id, u"") 
+                         for answer_id in problem.get_question_answers())
+    grading_results = problem.grade_answers(blank_answers)
+    try:
+        assert(all(result == 'incorrect' for result in grading_results.values()))
+    except AssertionError:
+        log.error("Blank accepted as correct answer in {0} for {1}"
+                  .format(problem,
+                          [answer_id for answer_id, result
+                           in sorted(grading_results.items())
+                           if result != 'incorrect']))
+
+
+def check_that_suggested_answers_work(problem):
+    """Split this up so that we're only used for formula/numeric answers.
+
+    Examples of where this fails:
+    * Displayed answers use units but acceptable ones do not.
+      - L1e0.xml
+      - Presents itself as UndefinedVariable (when it tries to pass to calc)
+    * "a or d" is what's displayed, but only "a" or "d" is accepted, not the 
+      string "a or d".
+      - L1-e00.xml
+    """
+    # These are actual answers we get from the responsetypes
+    real_answers = problem.get_question_answers()
+
+    # all_answers is real_answers + blanks for other answer_ids for which the
+    # responsetypes can't provide us pre-canned answers (customresponse)
+    all_answer_ids = problem.get_answer_ids()
+    all_answers = dict((answer_id, real_answers.get(answer_id, ""))
+                       for answer_id in all_answer_ids)
+
+    log.debug("Real answers: {0}".format(real_answers))
+    if real_answers:
+        try:
+            real_results = dict((answer_id, result) for answer_id, result 
+                                in problem.grade_answers(all_answers).items()
+                                if answer_id in real_answers)
+            log.debug(real_results)
+            assert(all(result == 'correct'
+                       for answer_id, result in real_results.items()))
+        except UndefinedVariable as uv_exc:
+            log.error("The variable \"{0}\" specified in the ".format(uv_exc) + 
+                      "solution isn't recognized (is it a units measure?).")
+        except AssertionError:
+            log.error("The following generated answers were not accepted for {0}:"
+                      .format(problem))
+            for question_id, result in sorted(real_results.items()):
+                if result != 'correct':
+                    log.error("  {0} = {1}".format(question_id, real_answers[question_id]))
+        except Exception as ex:
+            log.error("Uncaught error in {0}".format(problem))
+            log.exception(ex)
+
+def log_captured_output(output_stream, stream_name):
+    output_stream.seek(0)
+    output_text = output_stream.read()
+    if output_text:
+        log.info("##### Begin {0} #####\n".format(stream_name) + output_text)
+        log.info("##### End {0} #####".format(stream_name))
+
+
+if __name__ == '__main__':
+    sys.exit(main())
diff --git a/lms/templates/choicegroup.html b/common/lib/capa/templates/choicegroup.html
similarity index 100%
rename from lms/templates/choicegroup.html
rename to common/lib/capa/templates/choicegroup.html
diff --git a/lms/templates/imageinput.html b/common/lib/capa/templates/imageinput.html
similarity index 100%
rename from lms/templates/imageinput.html
rename to common/lib/capa/templates/imageinput.html
diff --git a/lms/templates/jstextline.html b/common/lib/capa/templates/jstextline.html
similarity index 100%
rename from lms/templates/jstextline.html
rename to common/lib/capa/templates/jstextline.html
diff --git a/lms/templates/mathstring.html b/common/lib/capa/templates/mathstring.html
similarity index 100%
rename from lms/templates/mathstring.html
rename to common/lib/capa/templates/mathstring.html
diff --git a/lms/templates/schematicinput.html b/common/lib/capa/templates/schematicinput.html
similarity index 100%
rename from lms/templates/schematicinput.html
rename to common/lib/capa/templates/schematicinput.html
diff --git a/lms/templates/solutionspan.html b/common/lib/capa/templates/solutionspan.html
similarity index 100%
rename from lms/templates/solutionspan.html
rename to common/lib/capa/templates/solutionspan.html
diff --git a/lms/templates/textinput.html b/common/lib/capa/templates/textinput.html
similarity index 100%
rename from lms/templates/textinput.html
rename to common/lib/capa/templates/textinput.html