@@ -38,5 +38,6 @@ cd test/chromium
 pip install --user -r requirements.txt
 cd -
 
-# Install a hook to run tests before pushing.
+# Install git hooks to run tests before committing and pushing.
 ln -sf ../../test.sh .git/hooks/pre-push
+ln -sf ../../test/commit.sh .git/hooks/pre-commit
@@ -0,0 +1,51 @@
+#!/bin/bash
+# Run https-everywhere-checker for each changed ruleset
+
+# Folder paths, relative to parent
+RULESETFOLDER="src/chrome/content/rules"
+RULETESTFOLDER="test/rules"
+
+# Go to git repo root; taken from ../test.sh. Note that
+# $GIT_DIR is .git in this case.
+if [ -n "$GIT_DIR" ]
+then
+  # $GIT_DIR is set, so we're running as a hook.
+  cd $GIT_DIR
+  cd ..
+else
+  # Git command exists? Cool, let's CD to the right place.
+  git rev-parse && cd "$(git rev-parse --show-toplevel)"
+fi
+
+RULESETS_CHANGED=$(git diff --name-only HEAD | grep $RULESETFOLDER | grep '.xml')
+
+# Only run test if something has changed.
+if [ "$RULESETS_CHANGED" ]; then
+  echo >&2 "Ruleset database has changed. Testing test URLs in all changed rulesets."
+
+  # Make a list of all changed rulesets, but exclude those
+  # that do not exist.
+  for RULESET in $RULESETS_CHANGED; do
+    # First check if the given ruleset actually exists
+    if [ ! -f $RULESET ]; then
+      echo >&2 "Skipped $RULESET; file not found."
+      continue
+    fi
+    TO_BE_TESTED="$TO_BE_TESTED $RULESET"
+  done
+
+  if [ "$TO_BE_TESTED" ]; then
+    # Do the actual test, using https-everywhere-checker.
+    TESTOUTPUT=$(python $RULETESTFOLDER/src/https_everywhere_checker/check_rules.py $RULETESTFOLDER/http.checker.config $TO_BE_TESTED 2>&1)
+    echo >&2 "$TESTOUTPUT"
+    # Unfortunately, no specific exit codes are available for connection
+    # failures, so we catch those with grep.
+    if [[ "$TESTOUTPUT" =~ "ERROR" ]]; then
+      echo >&2 "Test URL test failed."
+      exit 1
+    fi
+  fi
+  echo >&2 "Test URL test succeeded."
+fi
+
+exit 0