Change handling for course enrollment offsets.

Make courses appear (and count) if the courses have offsets, even if
they have no explicit enrollment counts since the offset date.  At
present, such courses are ignored, which results in an undercount for
total enrollment over all courses.

Change-Id: I67c4b6fba671a1bfc7024c566fe51212cb7eda44

edx/analytics/tasks/reports/enrollments.py

@@ -71,6 +71,12 @@ class CourseEnrollmentCountMixin(object):
                 # add them to the counts by the end of that day to
                 # get the correct count for the day.
                 count_by_day.loc[date, course_id] += count
+            else:
+                # We have an offset for the course, but no current
+                # counts.  Create an course entry, set the offset, and set
+                # all subsequent counts to zero.
+                count_by_day.loc[date, course_id] = count
+                count_by_day.loc[count_by_day.index > date, course_id] = 0
 
             # Flag values before the offset day with NaN,
             # since they are not "available".

edx/analytics/tasks/reports/tests/test_enrollments.py

+"""Tests for Enrollments-by-week report."""
+
 import datetime
 import textwrap
 from StringIO import StringIO
@@ -5,16 +7,16 @@ from StringIO import StringIO
 import luigi
 import luigi.hdfs
 from mock import MagicMock
-from numpy import isnan
+from numpy import isnan  # pylint: disable=no-name-in-module
 import pandas
 
 from edx.analytics.tasks.tests import unittest
 from edx.analytics.tasks.tests.target import FakeTarget
 from edx.analytics.tasks.reports.enrollments import EnrollmentsByWeek
-from edx.analytics.tasks.reports.enrollments import ExternalURL
 
 
 class TestEnrollmentsByWeek(unittest.TestCase):
+    """Tests for EnrollmentsByWeek report task."""
 
     def run_task(self, source, date, weeks, offset=None, statuses=None):
         """
@@ -36,7 +38,7 @@ class TestEnrollmentsByWeek(unittest.TestCase):
         # Mock the input and output targets
 
         def reformat(string):
-            # Reformat string to make it like a hadoop tsv
+            """Reformat string to make it like a TSV."""
             return textwrap.dedent(string).strip().replace(' ', '\t')
 
         input_targets = {
@@ -96,7 +98,8 @@ class TestEnrollmentsByWeek(unittest.TestCase):
         """
         res = self.run_task(source, '2013-01-21', 4)
         weeks = set(['2012-12-31', '2013-01-07', '2013-01-14', '2013-01-21'])
-        self.assertEqual(weeks | set(['org_id', 'status']), set(str(w) for w in res.columns))
+        self.assertEqual(weeks | set(['org_id', 'status']),
+                         set(str(w) for w in res.columns))
 
         course_1 = res.loc['course_1']
         self.assertTrue(isnan(course_1['2012-12-31']))  # no data
@@ -142,6 +145,7 @@ class TestEnrollmentsByWeek(unittest.TestCase):
         offset = """
         course_2 2013-03-07 8
         course_3 2013-03-15 6
+        course_4 2013-03-12 150000
         """
         res = self.run_task(source, '2013-03-28', 4, offset=offset)
 
@@ -154,6 +158,11 @@ class TestEnrollmentsByWeek(unittest.TestCase):
         self.assertTrue(isnan(course_3['2013-03-14']))  # no data
         self.assertEqual(course_3['2013-03-21'], 9)
 
+        course_4 = res.loc['course_4']
+        self.assertTrue(isnan(course_4['2013-03-07']))  # no data
+        self.assertEqual(course_4['2013-03-14'], 150000)
+        self.assertEqual(course_4['2013-03-21'], 150000)
+
     def test_unicode(self):
         course_id = u'course_\u2603'