diff --git a/t/Dockerfile b/t/Dockerfile
index 31692b6c..be612c03 100644
--- a/t/Dockerfile
+++ b/t/Dockerfile
@@ -5,10 +5,11 @@ FROM docker.mgm.sipwise.com/sipwise-bullseye:latest
 # is updated with the current date. It will force refresh of all
 # of the base images and things like `apt-get update` won't be using
 # old cached versions when the Dockerfile is built.
-ENV REFRESHED_AT 2021-07-01
+ENV REFRESHED_AT 2023-03-07
 
 RUN apt-get update && apt-get install --assume-yes python3-yaml python3-junitxml \
-  make libtemplate-perl libyaml-perl python3-pytest
+  make libtemplate-perl libyaml-perl python3-pytest \
+  && rm -rf /var/lib/apt/lists/*
 
 RUN echo './t/testrunner' >>/root/.bash_history
 
@@ -20,10 +21,6 @@ WORKDIR /code/
 # When you want to build the base image from scratch
 # (jump to the next section if you don't want to build yourself!):
 #
-# you need to put the proper NGCP sources at t/sources.list.d/builddeps.list
-# for instance, trunk:
-# echo "deb https://deb.sipwise.com/autobuild/ release-trunk-bullseye main" > t/sources.list.d/builddeps.list
-#
 # % docker build --tag="kamailio-config-tests-bullseye" -f t//Dockerfile .
 # % docker run --rm -i -t -v $(pwd):/code:rw kamailio-config-tests-bullseye:latest bash
 #
diff --git a/t/external/Dockerfile b/t/external/Dockerfile
new file mode 100644
index 00000000..484e8679
--- /dev/null
+++ b/t/external/Dockerfile
@@ -0,0 +1,33 @@
+# DOCKER_NAME=k-c-t-bullseye
+FROM docker.mgm.sipwise.com/sipwise-bullseye:latest
+
+# Important! Update this no-op ENV variable when this Dockerfile
+# is updated with the current date. It will force refresh of all
+# of the base images and things like `apt-get update` won't be using
+# old cached versions when the Dockerfile is built.
+ENV REFRESHED_AT 2023-03-07
+ENV BASE_DIR=/code
+
+RUN apt-get update && apt-get install --assume-yes \
+    parallel python3-yaml sip-tester tcpdump \
+    libconfig-tiny-perl libdata-dump-perl libjson-perl \
+    liblist-moreutils-perl libtemplate-perl libtext-csv-perl \
+    libtext-diff-perl libtry-tiny-perl libyaml-libyaml-perl \
+    libfile-slurp-perl libhash-merge-perl libwww-perl \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /code/
+################################################################################
+# Instructions for usage
+# ----------------------
+# When you want to build the base image from scratch
+# (jump to the next section if you don't want to build yourself!):
+#
+# % docker build --tag="k-c-t-bullseye" -f t/external/Dockerfile .
+# % docker run --rm -i -t -v $(pwd):/code:rw k-c-t-bullseye:latest bash
+#
+# Use the existing docker image:
+# % docker pull docker.mgm.sipwise.com/k-c-t-bullseye
+# % docker run --rm -i -t -v $(pwd):/code:rw docker.mgm.sipwise.com/k-c-t-bullseye:latest bash
+#
+################################################################################