diff --git a/.gitignore b/.gitignore
index c604a48..a722348 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 tests/dokku
 tests/fixtures
+tests/bin/plugn
diff --git a/README.md b/README.md
index 9f9ae33..1b67fd8 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,6 @@ dokku plugin:install https://github.com/dokku/dokku-mongo.git mongo
 ## commands
 
 ```
-mongo:alias <name> <alias>     Set an alias for the docker link
 mongo:clone <name> <new-name>  Create container <new-name> then copy data from <name> into <new-name>
 mongo:connect <name>           Connect via telnet to a mongo service
 mongo:create <name>            Create a mongo service
@@ -34,6 +33,7 @@ mongo:info <name>              Print the connection information
 mongo:link <name> <app>        Link the mongo service to the app
 mongo:list                     List all mongo services
 mongo:logs <name> [-t]         Print the most recent log(s) for this service
+mongo:promote <name> <app>     Promote service <name> as MONGO_URL in <app>
 mongo:restart <name>           Graceful shutdown and restart of the mongo service container
 mongo:start <name>             Start a previously stopped mongo service
 mongo:stop <name>              Stop a running mongo service
@@ -57,8 +57,6 @@ dokku mongo:create lolipop
 # get connection information as follows
 dokku mongo:info lolipop
 
-# lets assume the ip of our mongo service is 172.17.0.1
-
 # a mongo service can be linked to a
 # container this will use native docker
 # links via the docker-options plugin
@@ -68,24 +66,42 @@ dokku mongo:link lolipop playground
 
 # the above will expose the following environment variables
 #
-#   MONGO_URL=mongo://l:PASSWORD@172.17.0.1:27017/lolipop
-#   MONGO_NAME=/lolipop/DATABASE
-#   MONGO_PORT=tcp://172.17.0.1:27017
-#   MONGO_PORT_27017_TCP=tcp://172.17.0.1:27017
-#   MONGO_PORT_27017_TCP_PROTO=tcp
-#   MONGO_PORT_27017_TCP_PORT=27017
-#   MONGO_PORT_27017_TCP_ADDR=172.17.0.1
+#   DOKKU_MONGO_LOLIPOP_NAME=/lolipop/DATABASE
+#   DOKKU_MONGO_LOLIPOP_PORT=tcp://172.17.0.1:27017
+#   DOKKU_MONGO_LOLIPOP_PORT_27017_TCP=tcp://172.17.0.1:27017
+#   DOKKU_MONGO_LOLIPOP_PORT_27017_TCP_PROTO=tcp
+#   DOKKU_MONGO_LOLIPOP_PORT_27017_TCP_PORT=27017
+#   DOKKU_MONGO_LOLIPOP_PORT_27017_TCP_ADDR=172.17.0.1
+#
+# and the following will be set on the linked application by default
+#
+#   MONGO_URL=mongodb://lolipop:SOME_PASSWORD@dokku-mongo-lolipop:27017/lolipop
+#
+# NOTE: the host exposed here only works internally in docker containers. If
+# you want your container to be reachable from outside, you should use `expose`.
 
-# you can examine the environment variables
-# using our 'playground' app's env command
-dokku run playground env
+# another service can be linked to your app
+dokku mongo:link other_service playground
 
-# you can customize the environment
-# variables through a custom docker link alias
-dokku mongo:alias lolipop MONGO_DATABASE
+# since DATABASE_URL is already in use, another environment variable will be
+# generated automatically
+#
+#   DOKKU_MONGO_BLUE_URL=mongodb://other_service:ANOTHER_PASSWORD@dokku-mongo-other-service:27017/other_service
+
+# you can then promote the new service to be the primary one
+# NOTE: this will restart your app
+dokku mongo:promote other_service playground
+
+# this will replace MONGO_URL with the url from other_service and generate
+# another environment variable to hold the previous value if necessary.
+# you could end up with the following for example:
+#
+#   MONGO_URL=mongodb://other_service:ANOTHER_PASSWORD@dokku-mongo-other-service:27017/other_service
+#   DOKKU_MONGO_BLUE_URL=mongodb://other_service:ANOTHER_PASSWORD@dokku-mongo-other-service:27017/other_service
+#   DOKKU_MONGO_SILVER_URL=mongodb://lolipop:SOME_PASSWORD@dokku-mongo-lolipop:27017/lolipop
 
 # you can also unlink a mongo service
-# NOTE: this will restart your app
+# NOTE: this will restart your app and unset related environment variables
 dokku mongo:unlink lolipop playground
 
 # you can tail logs for a particular service
diff --git a/commands b/commands
index 39d851f..04272a7 100755
--- a/commands
+++ b/commands
@@ -16,13 +16,6 @@ if [[ $1 == $PLUGIN_COMMAND_PREFIX:* ]]; then
 fi
 
 case "$1" in
-  $PLUGIN_COMMAND_PREFIX:alias)
-    [[ -z $2 ]] && dokku_log_fail "Please specify a name for the service"
-    [[ -z $3 ]] && dokku_log_fail "Please specify an alias for the service"
-    verify_service_name "$2"
-    service_set_alias "$2" "$3"
-    ;;
-
   $PLUGIN_COMMAND_PREFIX:create)
     [[ -z $2 ]] && dokku_log_fail "Please specify a name for the service"
     [[ ! -d "$PLUGIN_DATA_ROOT/$2" ]] || dokku_log_fail "$PLUGIN_SERVICE service $2 already exists"
@@ -205,9 +198,16 @@ case "$1" in
     service_port_unexpose "$2"
     ;;
 
+  $PLUGIN_COMMAND_PREFIX:promote)
+    [[ -z $2 ]] && dokku_log_fail "Please specify a name for the service"
+    [[ -z $3 ]] && dokku_log_fail "Please specify an app to run the command on"
+    verify_service_name "$2"
+    verify_app_name "$3"
+    promote "$2" "$3"
+    ;;
+
   help | $PLUGIN_COMMAND_PREFIX:help)
     HELP=$(cat<<EOF
-    $PLUGIN_COMMAND_PREFIX:alias <name> <alias>, Set an alias for the docker link
     $PLUGIN_COMMAND_PREFIX:create <name>, Create a $PLUGIN_SERVICE service
     $PLUGIN_COMMAND_PREFIX:destroy <name>, Delete the $PLUGIN_SERVICE service and stop its container if there are no links left
     $PLUGIN_COMMAND_PREFIX:link <name> <app>, Link the $PLUGIN_SERVICE service to the app
@@ -224,6 +224,7 @@ case "$1" in
     $PLUGIN_COMMAND_PREFIX:unexpose <name>, Unexpose a previously exposed $PLUGIN_SERVICE service
     $PLUGIN_COMMAND_PREFIX:start <name>, Start a previously stopped $PLUGIN_SERVICE service
     $PLUGIN_COMMAND_PREFIX:stop <name>, Stop a running $PLUGIN_SERVICE service
+    $PLUGIN_COMMAND_PREFIX:promote <name> <app>, Promote service <name> as ${PLUGIN_DEFAULT_ALIAS}_URL in <app>
 EOF
 )
     if [[ -n $DOKKU_API_VERSION ]]; then
diff --git a/config b/config
index 7e55857..ff57ac0 100644
--- a/config
+++ b/config
@@ -7,6 +7,7 @@ export PLUGIN_COMMAND_PREFIX="mongo"
 export PLUGIN_DATA_ROOT=$MONGO_ROOT
 export PLUGIN_DATASTORE_PORTS=(27017 27018 27019 28017)
 export PLUGIN_DEFAULT_ALIAS="MONGO"
+export PLUGIN_ALT_ALIAS="DOKKU_MONGO"
 export PLUGIN_IMAGE=$MONGO_IMAGE
 export PLUGIN_IMAGE_VERSION=$MONGO_IMAGE_VERSION
 export PLUGIN_SCHEME="mongodb"
diff --git a/docker-args-build b/docker-args-build
deleted file mode 120000
index 68dea36..0000000
--- a/docker-args-build
+++ /dev/null
@@ -1 +0,0 @@
-docker-args-deploy
\ No newline at end of file
diff --git a/docker-args-deploy b/docker-args-deploy
deleted file mode 100755
index e56b2c8..0000000
--- a/docker-args-deploy
+++ /dev/null
@@ -1,31 +0,0 @@
-#!/usr/bin/env bash
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
-PLUGIN_BASE_PATH="$PLUGIN_PATH"
-if [[ -n $DOKKU_API_VERSION ]]; then
-  PLUGIN_BASE_PATH="$PLUGIN_ENABLED_PATH"
-fi
-source "$PLUGIN_BASE_PATH/common/functions"
-source "$(dirname "$0")/functions"
-source "$(dirname "$0")/config"
-
-STDIN=$(cat)
-APP="$1"
-
-output=""
-for i in $PLUGIN_DATA_ROOT/*; do
-  [[ -d $i ]] || continue
-  SERVICE=$(echo "$i" | cut -d'/' -f 7)
-  LINKS_FILE="$PLUGIN_DATA_ROOT/$SERVICE/LINKS"
-  ALIAS="$(service_alias "$SERVICE")"
-  SERVICE_URL="$(service_url "$SERVICE")"
-  if [[ -f "$LINKS_FILE" ]]; then
-    while read line; do
-      if [[ "$line" == "$APP" ]]; then
-        output="$output --link dokku.mongo.$SERVICE:$ALIAS --env ${ALIAS}_URL=$SERVICE_URL"
-        break
-      fi
-    done < "$LINKS_FILE"
-  fi
-done
-
-echo "$STDIN$output"
diff --git a/docker-args-run b/docker-args-run
deleted file mode 120000
index 68dea36..0000000
--- a/docker-args-run
+++ /dev/null
@@ -1 +0,0 @@
-docker-args-deploy
\ No newline at end of file
diff --git a/functions b/functions
index 7f53b15..864a496 100755
--- a/functions
+++ b/functions
@@ -32,14 +32,8 @@ verify_service_name() {
 
 service_alias() {
   local SERVICE="$1"
-  local ALIAS_FILE="$PLUGIN_DATA_ROOT/$SERVICE/ALIAS"
-
-  verify_service_name "$1"
-  if [[ -f "$ALIAS_FILE" ]]; then
-    cat "$ALIAS_FILE"
-  else
-    echo "$PLUGIN_DEFAULT_ALIAS"
-  fi
+  local SERVICE_NAME=$(get_service_name "$SERVICE")
+  echo "$SERVICE_NAME" | tr ._ -
 }
 
 service_info() {
@@ -77,16 +71,44 @@ service_exposed_ports() {
 service_link() {
   local APP="$2"
   local SERVICE="$1"
+  local SERVICE_URL=$(service_url "$SERVICE")
+  local SERVICE_NAME=$(get_service_name "$SERVICE")
   local SERVICE_ROOT="$PLUGIN_DATA_ROOT/$SERVICE"
+  local EXISTING_CONFIG=$(dokku config "$APP")
+  local LINK=$(echo "$EXISTING_CONFIG" | grep "$SERVICE_URL" | cut -d: -f1) || true
+  local DEFAULT_ALIAS=$(echo "$EXISTING_CONFIG" | grep "${PLUGIN_DEFAULT_ALIAS}_URL") || true
+  local SERVICE_ALIAS=$(service_alias "$SERVICE")
   local LINKS_FILE="$SERVICE_ROOT/LINKS"
 
+  [[ -n $LINK ]] && dokku_log_fail "Already linked as $LINK"
   mkdir -p "$SERVICE_ROOT" || dokku_log_fail "Unable to create service directory"
   touch "$LINKS_FILE"
   echo "$APP" >> "$LINKS_FILE"
   sort "$LINKS_FILE" -u -o "$LINKS_FILE"
 
-  dokku_log_info1 "Restarting app $APP"
-  dokku ps:restart "$APP"
+  local ALIAS="$PLUGIN_DEFAULT_ALIAS"
+  if [[ -n $DEFAULT_ALIAS ]]; then
+    ALIAS=$(service_alternative_alias "$EXISTING_CONFIG")
+  fi
+  dokku docker-options:add "$APP" build,deploy,run "--link $SERVICE_NAME:$SERVICE_ALIAS"
+  dokku config:set "$APP" "${ALIAS}_URL=$SERVICE_URL"
+}
+
+service_alternative_alias() {
+  local EXISTING_CONFIG="$1"
+  local COLORS=(AQUA BLACK BLUE FUCHSIA GRAY GREEN LIME MAROON NAVY OLIVE PURPLE RED SILVER TEAL WHITE YELLOW)
+  local ALIAS;
+
+  while [[ -z $ALIAS ]]; do
+    local IDX=$((RANDOM % ${#COLORS[*]}))
+    local COLOR=${COLORS[IDX]}
+    ALIAS="${PLUGIN_ALT_ALIAS}_${COLOR}"
+    local IN_USE=$(echo "$EXISTING_CONFIG" | grep "${ALIAS}_URL")
+    if [[ -n $IN_USE ]]; then
+      unset ALIAS
+    fi
+  done
+  echo "$ALIAS"
 }
 
 service_logs() {
@@ -232,25 +254,25 @@ service_stop() {
 service_unlink() {
   local APP="$2"
   local SERVICE="$1"
-  local SERVICE_ROOT="$PLUGIN_DATA_ROOT/$SERVICE"
-  local LINKS_FILE="$SERVICE_ROOT/LINKS"
+  local SERVICE_URL=$(service_url "$SERVICE")
+  local SERVICE_NAME=$(get_service_name "$SERVICE")
+  local EXISTING_CONFIG=$(dokku config "$APP")
+  local SERVICE_ALIAS=$(service_alias "$SERVICE")
+  local LINK=($(echo "$EXISTING_CONFIG" | grep "$SERVICE_URL" | cut -d: -f1)) || true
 
-  mkdir -p "$SERVICE_ROOT" || dokku_log_fail "Unable to create service directory"
-  touch "$LINKS_FILE"
-  sed -i "/^$APP\$/d" "$LINKS_FILE"
-  sort "$LINKS_FILE" -u -o "$LINKS_FILE"
+  [[ -z ${LINK[*]} ]] && dokku_log_fail "Not linked to app $APP"
+  remove_from_links_file "$SERVICE" "$APP"
 
-  dokku_log_info1 "Restarting app $APP"
-  dokku ps:restart "$APP"
+  dokku docker-options:remove "$APP" build,deploy,run "--link $SERVICE_NAME:$SERVICE_ALIAS"
+  dokku config:unset "$APP" "${LINK[*]}"
 }
 
 service_url() {
   local SERVICE="$1"
   local SERVICE_ROOT="$PLUGIN_DATA_ROOT/$SERVICE"
-  local ID="$(cat "$SERVICE_ROOT/ID")"
-  local IP="$(get_container_ip "$ID")"
   local PASSWORD="$(cat "$SERVICE_ROOT/PASSWORD")"
-  echo "$PLUGIN_SCHEME://$SERVICE:$PASSWORD@$IP:${PLUGIN_DATASTORE_PORTS[0]}/$SERVICE"
+  local SERVICE_ALIAS="$(service_alias "$SERVICE")"
+  echo "$PLUGIN_SCHEME://$SERVICE:$PASSWORD@$SERVICE_ALIAS:${PLUGIN_DATASTORE_PORTS[0]}/$SERVICE"
 }
 
 is_container_status () {
@@ -275,3 +297,46 @@ service_version() {
   local SERVICE_NAME="$(get_service_name "$SERVICE")"
   docker inspect -f '{{.Config.Image}}' "$SERVICE_NAME"
 }
+
+get_url_from_config() {
+  local EXISTING_CONFIG="$1"
+  local CONFIG_VAR="$2"
+  echo "$EXISTING_CONFIG" | grep "$CONFIG_VAR" | sed "s/$CONFIG_VAR:\s*//"
+}
+
+promote() {
+  local SERVICE="$1"
+  local APP="$2"
+  local PLUGIN_DEFAULT_CONFIG_VAR="${PLUGIN_DEFAULT_ALIAS}_URL"
+  local EXISTING_CONFIG=$(dokku config "$APP")
+  local SERVICE_URL=$(service_url "$SERVICE")
+  local CONFIG_VARS=($(echo "$EXISTING_CONFIG" | grep "$SERVICE_URL" | cut -d: -f1)) || true
+  local PREVIOUS_DEFAULT_URL=$(get_url_from_config "$EXISTING_CONFIG" "$PLUGIN_DEFAULT_CONFIG_VAR")
+
+  [[ -z ${CONFIG_VARS[*]} ]] && dokku_log_fail "Not linked to app $APP"
+  [[ ${CONFIG_VARS[*]} =~ $PLUGIN_DEFAULT_CONFIG_VAR ]] && dokku_log_fail "Service $1 already promoted as $PLUGIN_DEFAULT_CONFIG_VAR"
+
+  local NEW_CONFIG_VARS=""
+  if [[ -n $PREVIOUS_DEFAULT_URL ]]; then
+    local PREVIOUS_ALIAS=$(echo "$EXISTING_CONFIG" | grep "$PREVIOUS_DEFAULT_URL" | grep -v "$PLUGIN_DEFAULT_CONFIG_VAR") || true
+    if [[ -z $PREVIOUS_ALIAS ]]; then
+      local ALIAS=$(service_alternative_alias "$EXISTING_CONFIG")
+      NEW_CONFIG_VARS+="${ALIAS}_URL=$PREVIOUS_DEFAULT_URL "
+    fi
+  fi
+  local PROMOTE_URL=$(get_url_from_config "$EXISTING_CONFIG" "${CONFIG_VARS[0]}")
+  NEW_CONFIG_VARS+="$PLUGIN_DEFAULT_CONFIG_VAR=$PROMOTE_URL"
+  dokku config:set "$APP" $NEW_CONFIG_VARS
+}
+
+remove_from_links_file() {
+  local SERVICE="$1"
+  local APP="$2"
+  local SERVICE_ROOT="$PLUGIN_DATA_ROOT/$SERVICE"
+  local LINKS_FILE="$SERVICE_ROOT/LINKS"
+
+  mkdir -p "$SERVICE_ROOT" || dokku_log_fail "Unable to create service directory"
+  touch "$LINKS_FILE"
+  sed -i "/^$APP\$/d" "$LINKS_FILE"
+  sort "$LINKS_FILE" -u -o "$LINKS_FILE"
+}
diff --git a/pre-delete b/pre-delete
new file mode 100755
index 0000000..22897dc
--- /dev/null
+++ b/pre-delete
@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+PLUGIN_BASE_PATH="$PLUGIN_PATH"
+if [[ -n $DOKKU_API_VERSION ]]; then
+  PLUGIN_BASE_PATH="$PLUGIN_ENABLED_PATH"
+fi
+source "$PLUGIN_BASE_PATH/common/functions"
+source "$(dirname "$0")/functions"
+source "$(dirname "$0")/config"
+
+APP="$1"
+for SERVICE in "$PLUGIN_DATA_ROOT"/*; do
+  remove_from_links_file "$(basename "$SERVICE")" "$APP"
+done
+exit 0
diff --git a/tests/bin/sudo b/tests/bin/sudo
new file mode 100755
index 0000000..742e13d
--- /dev/null
+++ b/tests/bin/sudo
@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+exit 0
diff --git a/tests/hook_pre_delete.bats b/tests/hook_pre_delete.bats
new file mode 100755
index 0000000..62b79f4
--- /dev/null
+++ b/tests/hook_pre_delete.bats
@@ -0,0 +1,20 @@
+#!/usr/bin/env bats
+load test_helper
+
+setup() {
+  dokku apps:create my_app >&2
+  dokku "$PLUGIN_COMMAND_PREFIX:create" l >&2
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app >&2
+}
+
+teardown() {
+  dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app >&2
+  dokku --force "$PLUGIN_COMMAND_PREFIX:destroy" l >&2
+  rm "$DOKKU_ROOT/my_app" -rf
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:hook:pre-delete) removes app from links file when destroying app" {
+  [[ -n $(< "$PLUGIN_DATA_ROOT/l/LINKS") ]]
+  dokku --force apps:destroy my_app
+  [[ -z $(< "$PLUGIN_DATA_ROOT/l/LINKS") ]]
+}
diff --git a/tests/service_alias.bats b/tests/service_alias.bats
deleted file mode 100755
index 570f469..0000000
--- a/tests/service_alias.bats
+++ /dev/null
@@ -1,32 +0,0 @@
-#!/usr/bin/env bats
-load test_helper
-
-setup() {
-  dokku "$PLUGIN_COMMAND_PREFIX:create" l >&2
-}
-
-teardown() {
-  dokku --force "$PLUGIN_COMMAND_PREFIX:destroy" l >&2
-}
-
-@test "($PLUGIN_COMMAND_PREFIX:alias) error when there are no arguments" {
-  run dokku "$PLUGIN_COMMAND_PREFIX:alias"
-  assert_contains "${lines[*]}" "Please specify a name for the service"
-}
-
-@test "($PLUGIN_COMMAND_PREFIX:alias) error when alias is missing" {
-  run dokku "$PLUGIN_COMMAND_PREFIX:alias" l
-  assert_contains "${lines[*]}" "Please specify an alias for the service"
-}
-
-@test "($PLUGIN_COMMAND_PREFIX:alias) error when service does not exist" {
-  run dokku "$PLUGIN_COMMAND_PREFIX:alias" not_existing_service MY_ALIAS
-  assert_contains "${lines[*]}" "service not_existing_service does not exist"
-}
-
-@test "($PLUGIN_COMMAND_PREFIX:alias) success" {
-  run dokku "$PLUGIN_COMMAND_PREFIX:alias" l MY_ALIAS
-  new_alias=$(cat "$PLUGIN_DATA_ROOT/l/ALIAS")
-  [[ $new_alias == "MY_ALIAS" ]]
-}
-
diff --git a/tests/service_info.bats b/tests/service_info.bats
index 559efae..cd69d69 100755
--- a/tests/service_info.bats
+++ b/tests/service_info.bats
@@ -22,5 +22,13 @@ teardown() {
 @test "($PLUGIN_COMMAND_PREFIX:info) success" {
   run dokku "$PLUGIN_COMMAND_PREFIX:info" l
   password="$(cat "$PLUGIN_DATA_ROOT/l/PASSWORD")"
-  assert_contains "${lines[*]}" "DSN: mongodb://l:$password@172.17.0.34:27017/l"
+  assert_contains "${lines[*]}" "DSN: mongodb://l:$password@dokku-mongo-l:27017/l"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:info) replaces underscores by dash in hostname" {
+  dokku "$PLUGIN_COMMAND_PREFIX:create" test_with_underscores
+  run dokku "$PLUGIN_COMMAND_PREFIX:info" test_with_underscores
+  password="$(cat "$PLUGIN_DATA_ROOT/test_with_underscores/PASSWORD")"
+  assert_contains "${lines[*]}" "DSN: mongodb://test_with_underscores:$password@dokku-mongo-test-with-underscores:27017/test_with_underscores"
+  dokku --force "$PLUGIN_COMMAND_PREFIX:destroy" test_with_underscores
 }
diff --git a/tests/service_link.bats b/tests/service_link.bats
index df17c0d..fd18fcf 100755
--- a/tests/service_link.bats
+++ b/tests/service_link.bats
@@ -31,8 +31,31 @@ teardown() {
   assert_contains "${lines[*]}" "service not_existing_service does not exist"
 }
 
-@test "($PLUGIN_COMMAND_PREFIX:link) success" {
+@test "($PLUGIN_COMMAND_PREFIX:link) error when the service is already linked to app" {
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app
   run dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app
-  links=$(cat "$PLUGIN_DATA_ROOT/l/LINKS")
-  assert_equal "$links" "my_app"
+  assert_contains "${lines[*]}" "Already linked as MONGO_URL"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:link) exports MONGO_URL to app" {
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app
+  url=$(dokku config:get my_app MONGO_URL)
+  password="$(cat "$PLUGIN_DATA_ROOT/l/PASSWORD")"
+  assert_contains "$url" "mongodb://l:$password@dokku-mongo-l:27017/l"
+  dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:link) generates an alternate config url when MONGO_URL already in use" {
+  dokku config:set my_app MONGO_URL=mongodb://user:pass@host:27017/db
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app
+  run dokku config my_app
+  assert_contains "${lines[*]}" "DOKKU_MONGO_"
+  dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:link) links to app with docker-options" {
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app
+  run dokku docker-options my_app
+  assert_contains "${lines[*]}" "--link dokku.mongo.l:dokku-mongo-l"
+  dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
 }
diff --git a/tests/service_promote.bats b/tests/service_promote.bats
new file mode 100755
index 0000000..c708233
--- /dev/null
+++ b/tests/service_promote.bats
@@ -0,0 +1,55 @@
+#!/usr/bin/env bats
+load test_helper
+
+setup() {
+  dokku "$PLUGIN_COMMAND_PREFIX:create" l >&2
+  dokku apps:create my_app >&2
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app
+}
+
+teardown() {
+  dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
+  dokku --force "$PLUGIN_COMMAND_PREFIX:destroy" l >&2
+  rm "$DOKKU_ROOT/my_app" -rf
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:promote) error when there are no arguments" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:promote"
+  assert_contains "${lines[*]}" "Please specify a name for the service"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:promote) error when the app argument is missing" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:promote" l
+  assert_contains "${lines[*]}" "Please specify an app to run the command on"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:promote) error when the app does not exist" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:promote" l not_existing_app
+  assert_contains "${lines[*]}" "App not_existing_app does not exist"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:promote) error when the service does not exist" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:promote" not_existing_service my_app
+  assert_contains "${lines[*]}" "service not_existing_service does not exist"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:promote) error when the service is already promoted" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:promote" l my_app
+  assert_contains "${lines[*]}" "already promoted as MONGO_URL"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:promote) changes MONGO_URL" {
+  password="$(cat "$PLUGIN_DATA_ROOT/l/PASSWORD")"
+  dokku config:set my_app "MONGO_URL=mongodb://u:p@host:27017/db" "DOKKU_MONGO_BLUE_URL=mongodb://l:$password@dokku-mongo-l:27017/l"
+  dokku "$PLUGIN_COMMAND_PREFIX:promote" l my_app
+  url=$(dokku config:get my_app MONGO_URL)
+  assert_equal "$url" "mongodb://l:$password@dokku-mongo-l:27017/l"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:promote) creates new config url when needed" {
+  password="$(cat "$PLUGIN_DATA_ROOT/l/PASSWORD")"
+  dokku config:set my_app "MONGO_URL=mongodb://u:p@host:27017/db" "DOKKU_MONGO_BLUE_URL=mongodb://l:$password@dokku-mongo-l:27017/l"
+  dokku "$PLUGIN_COMMAND_PREFIX:promote" l my_app
+  run dokku config my_app
+  assert_contains "${lines[*]}" "DOKKU_MONGO_"
+}
diff --git a/tests/service_unlink.bats b/tests/service_unlink.bats
index 98233ad..e97093f 100755
--- a/tests/service_unlink.bats
+++ b/tests/service_unlink.bats
@@ -31,9 +31,21 @@ teardown() {
   assert_contains "${lines[*]}" "service not_existing_service does not exist"
 }
 
-@test "($PLUGIN_COMMAND_PREFIX:unlink) success" {
-  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app >&2
+@test "($PLUGIN_COMMAND_PREFIX:unlink) error when service not linked to app" {
   run dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
-  links=$(cat "$PLUGIN_DATA_ROOT/l/LINKS")
-  assert_equal "$links" ""
+  assert_contains "${lines[*]}" "Not linked to app my_app"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:unlink) removes link from docker-options" {
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app >&2
+  dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
+  options=$(dokku docker-options my_app)
+  assert_equal "$options" ""
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:unlink) unsets config url from app" {
+  dokku "$PLUGIN_COMMAND_PREFIX:link" l my_app >&2
+  dokku "$PLUGIN_COMMAND_PREFIX:unlink" l my_app
+  config=$(dokku config:get my_app MONGO_URL)
+  assert_equal "$config" ""
 }
diff --git a/tests/setup.sh b/tests/setup.sh
index a29514f..e5e0e5e 100644
--- a/tests/setup.sh
+++ b/tests/setup.sh
@@ -1,6 +1,8 @@
 #!/usr/bin/env bash
 source "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/test_helper.bash"
 
+BIN_STUBS="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/bin"
+
 if [[ ! -d $DOKKU_ROOT ]]; then
   git clone https://github.com/progrium/dokku.git $DOKKU_ROOT > /dev/null
 fi
@@ -13,3 +15,10 @@ cd -
 rm -rf $DOKKU_ROOT/plugins/service
 mkdir -p $DOKKU_ROOT/plugins/service
 find ./ -maxdepth 1 -type f -exec cp '{}' $DOKKU_ROOT/plugins/service \;
+
+if [[ ! -f $BIN_STUBS/plugn ]]; then
+  wget -O- "$PLUGN_URL" | tar xzf - -C "$BIN_STUBS"
+  plugn init
+  ln -s "$DOKKU_ROOT"/plugins/* "$DOKKU_ROOT"/plugins/available
+  ln -s "$DOKKU_ROOT"/plugins/* "$DOKKU_ROOT"/plugins/enabled
+fi
diff --git a/tests/test_helper.bash b/tests/test_helper.bash
index 560cbb5..67abfda 100644
--- a/tests/test_helper.bash
+++ b/tests/test_helper.bash
@@ -10,6 +10,7 @@ export PLUGIN_AVAILABLE_PATH="$PLUGIN_PATH"
 export PLUGIN_CORE_AVAILABLE_PATH="$PLUGIN_PATH"
 export MONGO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/fixtures"
 export PLUGIN_DATA_ROOT="$MONGO_ROOT"
+export PLUGN_URL="https://github.com/progrium/plugn/releases/download/v0.1.0/plugn_0.1.0_linux_x86_64.tgz"
 
 mkdir -p "$PLUGIN_DATA_ROOT"
 rm -rf "${PLUGIN_DATA_ROOT:?}"/*