add option to append coverage instead of deleting the .coverage file …

AUTHORS.rst

@@ -11,3 +11,4 @@ Authors
 * Federico Ceratto - http://firelet.net/
 * Josh Kalderimis - http://blog.cookiestack.com/
 * Ionel Cristian Mărieș - http://blog.ionelmc.ro
+* Christian Ledermann - https://github.com/cleder

README.rst

@@ -255,7 +255,9 @@ tests run on Travis-CI could produce a .coverage file for use with Coveralls.
 Coverage Data File
 ==================
 
-The data file is erased at the beginning of testing to ensure clean data for each test run.
+The data file is erased at the beginning of testing to ensure clean data for each test run. If you
+need to combine the overage of several test runs you can use the ``--cov-append`` option to append
+this coverage data to coverage data from previous test runs.
 
 The data file is left at the end of testing so that it is possible to use normal coverage tools to
 examine it.

src/pytest_cov/engine.py

@@ -111,7 +111,10 @@ def start(self):
 
         self.cov = coverage.coverage(source=self.cov_source,
                                      config_file=self.cov_config)
-        self.cov.erase()
+        if self.config.option.append_coverage:
+            self.cov.load()
+        else:
+            self.cov.erase()
         self.cov.start()
         self.set_env()
 

src/pytest_cov/plugin.py

@@ -35,6 +35,10 @@ def pytest_addoption(parser):
                          'default: False')
     group.addoption('--cov-fail-under', action='store', metavar='MIN', type='int',
                     help='Fail if the total coverage is less than MIN.')
+    group.addoption('--cov-append', action='store_true', default=False,
+                    dest='append_coverage',
+                    help='do not delete coverage but append to current, '
+                         'default: False')
 
 
 @pytest.mark.tryfirst

tests/test_pytest_cov.py

@@ -32,6 +32,16 @@ def test_foo():
         assert False
 '''
 
+SCRIPT2 = '''
+#
+
+def test_bar():
+    x = True
+    assert x
+
+'''
+
+
 COVERAGERC_SOURCE = '''\
 [run]
 source = .
@@ -717,3 +727,36 @@ def test_external_data_file_negative(testdir):
                                script)
     assert result.ret == 0
     assert glob.glob(str(testdir.tmpdir.join('.coverage*')))
+
+def test_append_coverage(testdir):
+    script = testdir.makepyfile(test_1=SCRIPT)
+    testdir.tmpdir.join('.coveragerc').write("")
+    result = testdir.runpytest('-v',
+                               '--cov=%s' % script.dirpath(),
+                               script)
+    size1 = script.dirpath().join('.coverage').size()
+    assert(size1 > 0)
+    script.remove()
+    script2 = testdir.makepyfile(test_2=SCRIPT2)
+    result = testdir.runpytest('-v', '--cov-append',
+                               '--cov=%s' % script2.dirpath(),
+                               script2)
+    size2 = script2.dirpath().join('.coverage').size()
+    assert(size2 > size1)
+
+def test_do_not_append_coverage(testdir):
+    script = testdir.makepyfile(test_1=SCRIPT)
+    testdir.tmpdir.join('.coveragerc').write("")
+    result = testdir.runpytest('-v',
+                               '--cov=%s' % script.dirpath(),
+                               script)
+    size1 = script.dirpath().join('.coverage').size()
+    assert(size1 > 0)
+    script.remove()
+    script2 = testdir.makepyfile(test_2=SCRIPT2)
+    result = testdir.runpytest('-v',
+                               '--cov=%s' % script2.dirpath(),
+                               script2)
+    size2 = script2.dirpath().join('.coverage').size()
+    assert(size1 > size2)
+    assert(size2 > 0)