diff --git a/jujucrashdump/crashdump.py b/jujucrashdump/crashdump.py
index e6c9411..4038f91 100755
--- a/jujucrashdump/crashdump.py
+++ b/jujucrashdump/crashdump.py
@@ -270,9 +270,12 @@ class CrashCollector(object):
         tar_cmd = (
             "sudo find {dirs} -mount -type f -size -{max_size}c -o -size "
             "{max_size}c 2>/dev/null | sudo tar -pcf /tmp/juju-dump-{uniq}.tar"
+            "{excludes}"
             " --files-from - 2>/dev/null"
         ).format(dirs=" ".join(directories),
                  max_size=self.max_size,
+                 excludes=''.join(
+                     [' --exclude {}'.format(x) for x in self.exclude]),
                  uniq=self.uniq)
         self._run_all(';'.join([
             tar_cmd,
diff --git a/tox.ini b/tox.ini
index 259c672..7585ac1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -14,8 +14,9 @@ deps =
 [testenv]
 commands = nosetests tests
 deps =
-    nose
     futures
+    mock
+    nose
     pyaml
 
 [travis]

diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..17dd8e7
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1,13 @@
+# Copyright 2020 Canonical Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/tests/test_jujucrashdump_crashdump.py b/tests/test_jujucrashdump_crashdump.py
new file mode 100644
index 0000000..158352c
--- /dev/null
+++ b/tests/test_jujucrashdump_crashdump.py
@@ -0,0 +1,77 @@
+# Copyright 2020 Canonical Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import mock
+
+import tests.utils as utils
+
+import jujucrashdump.crashdump as crashdump
+
+class TestCrashCollector(utils.BaseTestCase):
+
+    def setUp(self):
+        self.target = crashdump.CrashCollector('aModel', 42, ['extra_dir'])
+        self._patches = {}
+        self._patches_start = {}
+
+    def tearDown(self):
+        self.target = None
+        for k, v in self._patches.items():
+            v.stop()
+            setattr(self, k, None)
+        self._patches = None
+        self._patches_start = None
+
+    def patch_target(self, attr, return_value=None):
+        mocked = mock.patch.object(self.target, attr)
+        self._patches[attr] = mocked
+        started = mocked.start()
+        started.return_value = return_value
+        self._patches_start[attr] = started
+        setattr(self, attr, started)
+
+    def test_create_unit_tarballs(self):
+        self.patch_object(crashdump, 'DIRECTORIES')
+        self.target.uniq = 'fake-uuid'
+        self.patch_target('_run_all')
+        self.DIRECTORIES.__iter__.return_value = ['dir']
+        self.target.create_unit_tarballs()
+        self._run_all.assert_called_once_with(
+            'sudo find dir extra_dir /var/lib/lxd/containers/*/rootfsdir '
+            '/var/lib/lxd/containers/*/rootfsextra_dir -mount -type f '
+            '-size -42c -o -size 42c 2>/dev/null | '
+            'sudo tar -pcf /tmp/juju-dump-fake-uuid.tar '
+            '--files-from - 2>/dev/null;'
+            'sudo tar --append -f /tmp/juju-dump-fake-uuid.tar '
+            '-C /tmp/fake-uuid/cmd_output . || true;'
+            'sudo tar --append -f /tmp/juju-dump-fake-uuid.tar '
+            '-C /tmp/fake-uuid/ journalctl || true;'
+            'sudo tar --append -f /tmp/juju-dump-fake-uuid.tar '
+            '-C /tmp/fake-uuid/addon_output . || true')
+        self._run_all.reset_mock()
+        self.target.exclude = ('exc0', 'exc1')
+        self.target.create_unit_tarballs()
+        self._run_all.assert_called_once_with(
+            'sudo find dir extra_dir /var/lib/lxd/containers/*/rootfsdir '
+            '/var/lib/lxd/containers/*/rootfsextra_dir -mount -type f '
+            '-size -42c -o -size 42c 2>/dev/null | '
+            'sudo tar -pcf /tmp/juju-dump-fake-uuid.tar '
+            '--exclude exc0 --exclude exc1 '
+            '--files-from - 2>/dev/null;'
+            'sudo tar --append -f /tmp/juju-dump-fake-uuid.tar '
+            '-C /tmp/fake-uuid/cmd_output . || true;'
+            'sudo tar --append -f /tmp/juju-dump-fake-uuid.tar '
+            '-C /tmp/fake-uuid/ journalctl || true;'
+            'sudo tar --append -f /tmp/juju-dump-fake-uuid.tar '
+            '-C /tmp/fake-uuid/addon_output . || true')
diff --git a/tests/utils.py b/tests/utils.py
new file mode 100644
index 0000000..7ac4699
--- /dev/null
+++ b/tests/utils.py
@@ -0,0 +1,79 @@
+# Copyright 2016 Canonical Ltd
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Unit test helpers from https://github.com/openstack/charms.openstack/"""
+
+import contextlib
+import io
+import mock
+import unittest
+
+
+@contextlib.contextmanager
+def patch_open():
+    '''Patch open() to allow mocking both open() itself and the file that is
+    yielded.
+
+    Yields the mock for "open" and "file", respectively.'''
+    mock_open = mock.MagicMock(spec=open)
+    mock_file = mock.MagicMock(spec=io.FileIO)
+
+    @contextlib.contextmanager
+    def stub_open(*args, **kwargs):
+        mock_open(*args, **kwargs)
+        yield mock_file
+
+    with mock.patch('builtins.open', stub_open):
+        yield mock_open, mock_file
+
+
+class BaseTestCase(unittest.TestCase):
+
+    def setUp(self):
+        self._patches = {}
+        self._patches_start = {}
+
+    def tearDown(self):
+        for k, v in self._patches.items():
+            v.stop()
+            setattr(self, k, None)
+        self._patches = None
+        self._patches_start = None
+
+    def patch_object(self, obj, attr, return_value=None, name=None, new=None,
+                     **kwargs):
+        if name is None:
+            name = attr
+        if new is not None:
+            mocked = mock.patch.object(obj, attr, new=new, **kwargs)
+        else:
+            mocked = mock.patch.object(obj, attr, **kwargs)
+        self._patches[name] = mocked
+        started = mocked.start()
+        if new is None:
+            started.return_value = return_value
+        self._patches_start[name] = started
+        setattr(self, name, started)
+
+    def patch(self, item, return_value=None, name=None, new=None, **kwargs):
+        if name is None:
+            raise RuntimeError("Must pass 'name' to .patch()")
+        if new is not None:
+            mocked = mock.patch(item, new=new, **kwargs)
+        else:
+            mocked = mock.patch(item, **kwargs)
+        self._patches[name] = mocked
+        started = mocked.start()
+        if new is None:
+            started.return_value = return_value
+        self._patches_start[name] = started
+        setattr(self, name, started)

Exclude argument is not passed on to tar collecting data on units
It appears the exclude (-x / --exclude) was first developed for a specific set of juju specific files.

Since juju crashdump now also collects data from other places on the system, it would be useful to pass the exclude list on to the tar command collecting data elsewhere too.

https://github.com/juju/juju-crashdump/blob/2ec95c6a0e51dfae2410136652e01ed84d3a7fb1/jujucrashdump/crashdump.py#L270-L282
tests/test_jujucrashdump_crashdump.py::TestCrashCollector::test_create_unit_tarballs