Add test coverage measurement and reporting

- Implement coverage functionality as a setuptools Command subclass
  (in plinth/tests/coverage/test_coverage.py)
- Register the new 'test_coverage' command in setup.py
- Modify the INSTALL file to specify python3-coverage as a new dependency
- Modify the HACKING file to document the new 'test_coverage' command
- Have git (via .gitignore) ignore the '.coverage' output data file and
  the contents of the 'plinth/tests/coverage/report' directory

.gitignore

@@ -28,3 +28,5 @@ build/
 .emacs.desktop*
 *.egg-info/
 dist/
+.coverage
+plinth/tests/coverage/report/

HACKING

@@ -8,7 +8,7 @@
     $ sudo python3 setup.py develop
 
     This will install the python package in a special development mode.  Run it
-    normally.  Any updates to the code (and core pakcage data files) do not
+    normally.  Any updates to the code (and core package data files) do not
     require re-installation after every modification.
 
     CherryPy web server also monitors changes to the source files and reloads
@@ -28,7 +28,7 @@
     *Note:* This mode is supported only in a limited manner.  The following are
     the unknown issues with it:
 
-    1. Help pages are also not built. Run 'make -C doc' manaully.
+    1. Help pages are also not built. Run 'make -C doc' manually.
 
     2. Actions do not work when running as normal user without 'sudo' prefix.
        You need to add 'actions' directory to be allowed for 'sudo' commands.
@@ -40,6 +40,24 @@
 
     $ python3 setup.py test
 
+## Running the Test Coverage Analysis
+
+1. Run the coverage tool:
+
+    $ python3 setup.py test_coverage
+
+    Invoking this command generates a binary-format '.coverage' data file in
+    the top-level project directory which is recreated with each run, and
+    writes a set of HTML and other supporting files which comprise the
+    browsable coverage report to the 'plinth/tests/coverage/report' directory.
+    Index.html presents the coverage summary, broken down by module.  Data
+    columns can be sorted by clicking on the column header or by using mnemonic
+    hot-keys specified in the keyboard widget in the upper-right corner of the
+    page.  Clicking on the name of a particular source file opens a page that
+    displays the contents of that file, with color-coding in the left margin to
+    indicate which statements or branches were executed via the tests (green)
+    and which statements or branches were not executed (red).
+
 ## Testing Inside a Virtual Machine
 
 1. Checkout source on the host.
@@ -96,6 +114,8 @@ infrastructure in place for it from the start.  Use it like this:
 
 * *CherryPy3* - WSGI web server since Django does not have proper web server
 
+* *Coverage* - Test coverage measurement and reporting tool
+
 * *Django* - Web application framework for Plinth
 
 * *JQuery* - Javascript framework used for convenience

INSTALL

@@ -6,7 +6,8 @@
 
     $ sudo apt-get install libjs-jquery libjs-modernizr \
     libjs-bootstrap make pandoc python3 python3-cherrypy3 \
-    python3-django python3-bootstrapform python3-setuptools
+    python3-coverage python3-django python3-bootstrapform \
+    python3-setuptools
 
 2. Install Plinth:
 

plinth/tests/coverage/test_coverage.py

@@ -0,0 +1,80 @@
+#!/usr/bin/python3
+# -*- mode: python; mode: auto-fill; fill-column: 80 -*-
+
+"""Support for integration of code test coverage analysis with setuptools.
+
+Derived from 'Adding Test Code Coverage Analysis to a Python Project’s Setup Command'
+<http://jeetworks.org/adding-test-code-coverage-analysis-to-a-python-projects-setup-command/>
+"""
+
+import coverage
+import glob
+import setuptools
+import shutil
+import time
+import unittest
+
+from plinth import tests
+
+
+# project directories with testable source code
+SOURCE_DIRS = ['plinth'] + glob.glob('plinth/modules/*')
+
+# files to exclude from coverage analysis and reporting
+FILES_TO_OMIT = ['plinth/tests/*.py']
+
+# location of coverage HTML report files
+COVERAGE_REPORT_DIR = 'plinth/tests/coverage/report'
+
+
+class TestCoverageCommand(setuptools.Command):
+    """
+    Subclass of setuptools Command to perform code test coverage analysis.
+    """
+
+    description = "Run test coverage analysis"
+    user_options = [
+        ('test-module=', 't', "Explicitly specify a single module to test")
+    ]
+
+    def initialize_options(self):
+        """
+        Initialize options to default values.
+        """
+        self.test_module = None
+
+    def finalize_options(self):
+        pass
+
+    def run(self):
+        """
+        Main command implementation.
+        """
+
+        # erase any existing HTML report files
+        try:
+            shutil.rmtree(COVERAGE_REPORT_DIR, True)
+        except:
+            pass
+
+        # initialize a test suite for one or all modules
+        if self.test_module is None:
+            test_suite = tests.TEST_SUITE
+        else:
+            test = unittest.defaultTestLoader.loadTestsFromNames([self.test_module])
+            test_suite = unittest.TestSuite(test)
+
+        # run the coverage analysis
+        runner = unittest.TextTestRunner()
+        cov = coverage.coverage(auto_data=True, branch=True, source=SOURCE_DIRS,
+                                omit=FILES_TO_OMIT)
+        cov.erase()     # erase existing coverage data file
+        cov.start()
+        runner.run(test_suite)
+        cov.stop()
+
+        # generate an HTML report
+        html_report_title = ("FreedomBox:Plinth -- Test Coverage as of " +
+                             time.strftime("%x %X %Z"))
+        cov.html_report(directory=COVERAGE_REPORT_DIR, omit=FILES_TO_OMIT,
+                        title=html_report_title)

setup.py

@@ -31,6 +31,7 @@ import shutil
 import subprocess
 
 from plinth import __version__
+from plinth.tests.coverage import test_coverage
 
 
 DIRECTORIES_TO_CREATE = [
@@ -113,7 +114,8 @@ setuptools.setup(
     install_requires=[
         'cherrypy >= 3.0',
         'django >= 1.7.0',
-        'django-bootstrap-form'
+        'django-bootstrap-form',
+        'coverage >= 3.7'
     ],
     include_package_data=True,
     package_data={'plinth': ['templates/*',
@@ -134,6 +136,9 @@ setuptools.setup(
                 ('/etc/plinth/modules-enabled',
                  glob.glob(os.path.join('data/etc/plinth/modules-enabled',
                                         '*')))],
-    cmdclass={'clean': CustomClean,
+    cmdclass={
-              'install_data': CustomInstallData},
+        'clean': CustomClean,
+        'install_data': CustomInstallData,
+        'test_coverage': test_coverage.TestCoverageCommand
+    },
 )