diff --git a/.gitignore b/.gitignore
index 1ae7eac65..8ae61778d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -23,6 +23,7 @@ pip-log.txt
 # Unit test / coverage reports
 .coverage
 cover
+cover-master
 .tox
 nosetests.xml
 .testrepository
diff --git a/tools/cover.sh b/tools/cover.sh
new file mode 100755
index 000000000..7566d6a02
--- /dev/null
+++ b/tools/cover.sh
@@ -0,0 +1,71 @@
+#!/bin/bash
+#
+#    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.
+
+ALLOWED_EXTRA_MISSING=0
+
+show_diff () {
+    head -1 $1
+    diff -U 0 $1 $2 | sed 1,2d
+}
+
+if ! git diff --exit-code || ! git diff --cached --exit-code
+then
+    echo "There are uncommitted changes!"
+    echo "Please clean git working directory and try again"
+    exit 1
+fi
+
+# Checkout master and save coverage report
+git checkout HEAD^
+
+base_op_count=`grep "op\." -R zun/db/sqlalchemy/alembic/versions/ | wc -l`
+baseline_report=$(mktemp -t zun_coverageXXXXXXX)
+find . -type f -name "*.pyc" -delete && python setup.py testr --coverage --testr-args="$*"
+coverage report > $baseline_report
+mv cover cover-master
+cat $baseline_report
+baseline_missing=$(awk 'END { print $3 }' $baseline_report)
+
+# Checkout back and save coverage report
+git checkout -
+
+current_op_count=`grep "op\." -R zun/db/sqlalchemy/alembic/versions/ | wc -l`
+current_report=$(mktemp -t zun_coverageXXXXXXX)
+find . -type f -name "*.pyc" -delete && python setup.py testr --coverage --testr-args="$*"
+coverage report > $current_report
+current_missing=$(awk 'END { print $3 }' $current_report)
+
+# Show coverage details
+allowed_missing=$((baseline_missing+ALLOWED_EXTRA_MISSING+current_op_count-base_op_count))
+
+echo "Allowed to introduce missing lines : ${ALLOWED_EXTRA_MISSING}"
+echo "Missing lines in master            : ${baseline_missing}"
+echo "Missing lines in proposed change   : ${current_missing}"
+
+if [ $allowed_missing -ge $current_missing ]; then
+    if [ $baseline_missing -lt $current_missing ]; then
+        show_diff $baseline_report $current_report
+        echo "We believe you can test your code with 100% coverage!"
+    else
+        echo "Thank you! You are awesome! Keep writing unit tests! :)"
+    fi
+    exit_code=0
+else
+    show_diff $baseline_report $current_report
+    echo "Please write more unit tests, we must maintain our test coverage :( "
+    exit_code=1
+fi
+
+rm $baseline_report $current_report
+exit $exit_code
diff --git a/tox.ini b/tox.ini
index 5a1ffc226..cb8eed55b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -31,8 +31,7 @@ commands =
 commands = {posargs}
 
 [testenv:cover]
-commands = python setup.py test --coverage --testr-args='{posargs}'
-           coverage report
+commands = {toxinidir}/tools/cover.sh {posargs}
 
 [testenv:docs]
 commands =