Add tests for c-ares wrapper using a local DNS server.
diff --git a/tools/dockerfile/test/php_jessie_x64/Dockerfile b/tools/dockerfile/test/php_jessie_x64/Dockerfile
index 245a642..ae82a8d 100644
--- a/tools/dockerfile/test/php_jessie_x64/Dockerfile
+++ b/tools/dockerfile/test/php_jessie_x64/Dockerfile
@@ -22,6 +22,7 @@
bzip2 \
ccache \
curl \
+ dnsutils \
gcc \
gcc-multilib \
git \
@@ -65,7 +66,7 @@
# Install Python packages from PyPI
RUN pip install pip --upgrade
RUN pip install virtualenv
-RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.2.0 six==1.10.0
+RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.2.0 six==1.10.0 twisted==17.5.0
#=================
# PHP dependencies