Revert "Revert "refactor: move common/lib/capa/capa to xmodule/capa" (#30762)"

This reverts commit 4463ee751d.

xmodule/capa/tests/test_customrender.py

@@ -0,0 +1,80 @@
+# lint-amnesty, pylint: disable=missing-module-docstring
+
+import unittest
+import xml.sax.saxutils as saxutils
+
+from lxml import etree
+
+from xmodule.capa import customrender
+from xmodule.capa.tests.helpers import test_capa_system
+
+# just a handy shortcut
+lookup_tag = customrender.registry.get_class_for_tag
+
+
+def extract_context(xml):
+    """
+    Given an xml element corresponding to the output of test_capa_system.render_template, get back the
+    original context
+    """
+    return eval(xml.text)  # lint-amnesty, pylint: disable=eval-used
+
+
+def quote_attr(s):
+    return saxutils.quoteattr(s)[1:-1]  # don't want the outer quotes
+
+
+class HelperTest(unittest.TestCase):
+    '''
+    Make sure that our helper function works!
+    '''
+    def check(self, d):
+        xml = etree.XML(test_capa_system().render_template('blah', d))
+        assert d == extract_context(xml)
+
+    def test_extract_context(self):
+        self.check({})
+        self.check({1, 2})
+        self.check({'id', 'an id'})
+        self.check({'with"quote', 'also"quote'})
+
+
+class SolutionRenderTest(unittest.TestCase):
+    '''
+    Make sure solutions render properly.
+    '''
+
+    def test_rendering(self):
+        solution = 'To compute unicorns, count them.'
+        xml_str = """<solution id="solution_12">{s}</solution>""".format(s=solution)
+        element = etree.fromstring(xml_str)
+
+        renderer = lookup_tag('solution')(test_capa_system(), element)
+
+        assert renderer.id == 'solution_12'
+
+        # Our test_capa_system "renders" templates to a div with the repr of the context.
+        xml = renderer.get_html()
+        context = extract_context(xml)
+        assert context == {'id': 'solution_12'}
+
+
+class MathRenderTest(unittest.TestCase):
+    '''
+    Make sure math renders properly.
+    '''
+
+    def check_parse(self, latex_in, mathjax_out):  # lint-amnesty, pylint: disable=missing-function-docstring
+        xml_str = """<math>{tex}</math>""".format(tex=latex_in)
+        element = etree.fromstring(xml_str)
+
+        renderer = lookup_tag('math')(test_capa_system(), element)
+
+        assert renderer.mathstr == mathjax_out
+
+    def test_parsing(self):
+        self.check_parse('$abc$', '[mathjaxinline]abc[/mathjaxinline]')
+        self.check_parse('$abc', '$abc')
+        self.check_parse(r'$\displaystyle 2+2$', '[mathjax] 2+2[/mathjax]')
+
+    # NOTE: not testing get_html yet because I don't understand why it's doing what it's doing.