diff --git a/build/build.sh b/build/build.sh
index 25d3515b..92db534f 100644
--- a/build/build.sh
+++ b/build/build.sh
@@ -36,11 +36,7 @@ EOF
     echo "weave:*:::::::" >>/etc/shadow
     echo "weave	ALL=(ALL)	NOPASSWD: ALL" >>/etc/sudoers
 
-    if [ "$1" = "tests" ] ; then
-        su weave -c "PATH=$PATH make -C $WEAVE_SRC tests"
-    else
-        su weave -c "PATH=$PATH make -C $WEAVE_SRC build"
-    fi
+    su weave -c "PATH=$PATH make -C $WEAVE_SRC build"
 else
     # There are arguments to pass to git-clone
     mkdir -p ${WEAVE_SRC%/*}
diff --git a/circle.yml b/circle.yml
index 70117e68..63bcc109 100644
--- a/circle.yml
+++ b/circle.yml
@@ -12,18 +12,19 @@ machine:
     SRCDIR: /home/ubuntu/src/github.com/weaveworks/weave
     PATH: $PATH:$HOME/.local/bin:$HOME/google-cloud-sdk/bin/
     CLOUDSDK_CORE_DISABLE_PROMPTS: 1
-    WEAVE_BUILD: $HOME/docker/weave-build.tar
+    WEAVE_TEST: $HOME/docker/weave-test.tar
 
 dependencies:
   cache_directories:
     - "~/docker"
   override:
-    - if [[ -e "$WEAVE_BUILD" ]]; then
-        docker load -i $WEAVE_BUILD;
+    - if [[ -e "$WEAVE_TEST" ]]; then
+        docker load -i $WEAVE_TEST;
       else
         docker build -t weaveworks/weave-build build;
-        mkdir -p $(dirname "$WEAVE_BUILD");
-        docker save weaveworks/weave-build >$WEAVE_BUILD;
+        docker build -t weaveworks/weave-test test/image;
+        mkdir -p $(dirname "$WEAVE_TEST");
+        docker save weaveworks/weave-test >$WEAVE_TEST;
       fi
   post:
     - sudo apt-get update
@@ -36,7 +37,7 @@ dependencies:
 
 test:
   override:
-    - docker run -v /var/run/docker.sock:/run/docker.sock -v /home/ubuntu:/home/go -e COVERDIR=test/coverage -e SLOW=true -e CIRCLECI -e CIRCLE_BUILD_NUM -e CIRCLE_NODE_TOTAL -e CIRCLE_NODE_INDEX weaveworks/weave-build tests:
+    - docker run -v /home/ubuntu:/home/go -e COVERDIR=test/coverage -e SLOW=true -e CIRCLECI -e CIRCLE_BUILD_NUM -e CIRCLE_NODE_TOTAL -e CIRCLE_NODE_INDEX weaveworks/weave-test:
         parallel: true
     - docker run -v /var/run/docker.sock:/run/docker.sock -v /home/ubuntu:/home/go -e COVERAGE=true weaveworks/weave-build:
         parallel: true
diff --git a/test/image/Dockerfile b/test/image/Dockerfile
new file mode 100644
index 00000000..c8f62174
--- /dev/null
+++ b/test/image/Dockerfile
@@ -0,0 +1,3 @@
+FROM weaveworks/weave-build
+COPY test.sh /
+ENTRYPOINT ["sh", "/test.sh"]
diff --git a/test/image/test.sh b/test/image/test.sh
new file mode 100644
index 00000000..1b137b24
--- /dev/null
+++ b/test/image/test.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+set -e
+
+GOPATH=/home/go
+export GOPATH
+
+WEAVE_SRC=$GOPATH/src/github.com/weaveworks/weave
+
+# Expect that the weave repo will be bind-mounted into $GOPATH
+if ! [ -e $WEAVE_SRC ] ; then
+    cat 2>&1 <<EOF
+Nothing at ${WEAVE_SRC}.  Please
+bind-mount the golang workspace containing weave with the
+docker run -v option, e.g.:
+
+$ docker run -v <host gopath>:${GOPATH} \\
+      weaveworks/weave-test
+EOF
+    exit 1
+fi
+
+# If we run make directly, any files created on the bind mount
+# will have awkward ownership.  So we switch to a user with the
+# same user and group IDs as source directory.  We have to set a
+# few things up so that sudo works without complaining later on.
+uid=$(stat --format="%u" $WEAVE_SRC)
+gid=$(stat --format="%g" $WEAVE_SRC)
+echo "weave:x:$uid:$gid::$WEAVE_SRC:/bin/sh" >>/etc/passwd
+echo "weave:*:::::::" >>/etc/shadow
+echo "weave	ALL=(ALL)	NOPASSWD: ALL" >>/etc/sudoers
+
+su weave -c "PATH=$PATH make -C $WEAVE_SRC tests"
+