diff --git a/test/mail_dhparams_manual_not_one_dir.bats b/test/mail_dhparams_manual_not_one_dir.bats
index f2072a8b..928e3bb3 100644
--- a/test/mail_dhparams_manual_not_one_dir.bats
+++ b/test/mail_dhparams_manual_not_one_dir.bats
@@ -21,12 +21,12 @@ function teardown() {
 }
 
 function setup_file() {
-    private_config=$(duplicate_config_for_container .)
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     # copy the custom DHE params in local config
-    cp "`pwd`/test/test-files/ssl/custom-dhe-params.pem" "${private_config}/dhparams.pem"
+    cp "`pwd`/test/test-files/ssl/custom-dhe-params.pem" "${PRIVATE_CONFIG}/dhparams.pem"
 
     docker run -d --name mail_manual_dhparams_not_one_dir \
-		-v "${private_config}":/tmp/docker-mailserver \
+		-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 		-v "`pwd`/test/test-files":/tmp/docker-mailserver-test:ro \
 		-e DMS_DEBUG=0 \
 		-e ONE_DIR=0 \
diff --git a/test/mail_lmtp_ip.bats b/test/mail_lmtp_ip.bats
index 02547436..42ad9639 100644
--- a/test/mail_lmtp_ip.bats
+++ b/test/mail_lmtp_ip.bats
@@ -43,7 +43,7 @@ teardown_file() {
   wait_for_smtp_port_in_container mail_lmtp_ip
   run docker exec mail_lmtp_ip /bin/sh -c "nc 0.0.0.0 25 < /tmp/docker-mailserver-test/email-templates/existing-user1.txt"
   assert_success
-  
+
   # polling needs to avoid wc -l's unconditionally successful return status
   repeat_until_success_or_timeout 60 docker exec mail_lmtp_ip /bin/sh -c "grep 'postfix/lmtp' /var/log/mail/mail.log | grep 'status=sent' | grep ' Saved)'"
   run docker exec mail_lmtp_ip /bin/sh -c "grep 'postfix/lmtp' /var/log/mail/mail.log | grep 'status=sent' | grep ' Saved)' | wc -l"
@@ -53,4 +53,4 @@ teardown_file() {
 
 @test "last" {
     skip 'only used to call teardown_file from teardown'
-}
\ No newline at end of file
+}
diff --git a/test/mail_ssl_letsencrypt.bats b/test/mail_ssl_letsencrypt.bats
index c6e74a91..45714509 100644
--- a/test/mail_ssl_letsencrypt.bats
+++ b/test/mail_ssl_letsencrypt.bats
@@ -9,31 +9,31 @@ function teardown() {
 }
 
 function setup_file() {
-  private_config="$(duplicate_config_for_container . mail_lets_domain)"
+  PRIVATE_CONFIG="$(duplicate_config_for_container . mail_lets_domain)"
   docker run -d --name mail_lets_domain \
-  -v "${private_config}":/tmp/docker-mailserver \
+  -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
   -v "`pwd`/test/test-files":/tmp/docker-mailserver-test:ro \
-  -v "${private_config}/letsencrypt/my-domain.com":/etc/letsencrypt/live/my-domain.com \
+  -v "${PRIVATE_CONFIG}/letsencrypt/my-domain.com":/etc/letsencrypt/live/my-domain.com \
   -e DMS_DEBUG=0 \
   -e SSL_TYPE=letsencrypt \
   -h mail.my-domain.com -t ${NAME}
   wait_for_finished_setup_in_container mail_lets_domain
 
-  private_config="$(duplicate_config_for_container . mail_lets_hostname)"
+  PRIVATE_CONFIG="$(duplicate_config_for_container . mail_lets_hostname)"
   docker run -d --name mail_lets_hostname \
-  -v "${private_config}":/tmp/docker-mailserver \
+  -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
   -v "`pwd`/test/test-files":/tmp/docker-mailserver-test:ro \
-  -v "${private_config}/letsencrypt/mail.my-domain.com":/etc/letsencrypt/live/mail.my-domain.com \
+  -v "${PRIVATE_CONFIG}/letsencrypt/mail.my-domain.com":/etc/letsencrypt/live/mail.my-domain.com \
   -e DMS_DEBUG=0 \
   -e SSL_TYPE=letsencrypt \
   -h mail.my-domain.com -t ${NAME}
   wait_for_finished_setup_in_container mail_lets_hostname
 
-  private_config="$(duplicate_config_for_container . mail_lets_acme_json)"
+  PRIVATE_CONFIG="$(duplicate_config_for_container . mail_lets_acme_json)"
   cp "$(private_config_path mail_lets_acme_json)/letsencrypt/acme.json" "$(private_config_path mail_lets_acme_json)/acme.json"
   docker run -d --name mail_lets_acme_json \
-    -v "${private_config}":/tmp/docker-mailserver \
-    -v "${private_config}/acme.json":/etc/letsencrypt/acme.json:ro \
+    -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
+    -v "${PRIVATE_CONFIG}/acme.json":/etc/letsencrypt/acme.json:ro \
     -v "`pwd`/test/test-files":/tmp/docker-mailserver-test:ro \
     -e DMS_DEBUG=0 \
     -e SSL_TYPE=letsencrypt \
diff --git a/test/test_helper.bats b/test/test_helper.bats
index 30f791b6..f69b368b 100644
--- a/test/test_helper.bats
+++ b/test/test_helper.bats
@@ -5,13 +5,13 @@ load 'test_helper/common'
 @test "repeat_until_success_or_timeout returns instantly on success" {
     SECONDS=0
     repeat_until_success_or_timeout 1 true
-    [[ $SECONDS -le 1 ]]
+    [[ ${SECONDS} -le 1 ]]
 }
 
 @test "repeat_until_success_or_timeout waits for timeout on persistent failure" {
     SECONDS=0
     run repeat_until_success_or_timeout 2 false
-    [[ $SECONDS -ge 2 ]]
+    [[ ${SECONDS} -ge 2 ]]
     assert_failure
     assert_output --partial "Timed out on command"
 }
@@ -19,7 +19,7 @@ load 'test_helper/common'
 @test "repeat_until_success_or_timeout aborts immediately on fatal failure" {
     SECONDS=0
     run repeat_until_success_or_timeout --fatal-test false 2 false
-    [[ $SECONDS -le 1 ]]
+    [[ ${SECONDS} -le 1 ]]
     assert_failure
     assert_output --partial "early aborting"
 }
@@ -30,7 +30,7 @@ load 'test_helper/common'
 
     run repeat_until_success_or_timeout timeout true
     assert_failure
-    
+
     run repeat_until_success_or_timeout --fatal-test true timeout true
     assert_failure
 }
@@ -38,44 +38,44 @@ load 'test_helper/common'
 @test "run_until_success_or_timeout returns instantly on success" {
     SECONDS=0
     run_until_success_or_timeout 2 true
-    [[ $SECONDS -le 1 ]]
+    [[ ${SECONDS} -le 1 ]]
     assert_success
 }
 
 @test "run_until_success_or_timeout waits for timeout on persistent failure" {
     SECONDS=0
     ! run_until_success_or_timeout 2 false
-    [[ $SECONDS -ge 2 ]]
+    [[ ${SECONDS} -ge 2 ]]
     assert_failure
 }
 
 @test "repeat_in_container_until_success_or_timeout fails immediately for non-running container" {
     SECONDS=0
     ! repeat_in_container_until_success_or_timeout 10 name-of-non-existing-container true
-    [[ $SECONDS -le 1 ]]
+    [[ ${SECONDS} -le 1 ]]
 }
 
 @test "repeat_in_container_until_success_or_timeout run command in container" {
     local CONTAINER_NAME=$(docker run --rm -d alpine sleep 100)
     SECONDS=0
-    ! repeat_in_container_until_success_or_timeout 10 "$CONTAINER_NAME" sh -c "echo '$CONTAINER_NAME' > /tmp/marker"
-    [[ $SECONDS -le 1 ]]
-    run docker exec "$CONTAINER_NAME" cat /tmp/marker
-    assert_output "$CONTAINER_NAME"
+    ! repeat_in_container_until_success_or_timeout 10 "${CONTAINER_NAME}" sh -c "echo '${CONTAINER_NAME}' > /tmp/marker"
+    [[ ${SECONDS} -le 1 ]]
+    run docker exec "${CONTAINER_NAME}" cat /tmp/marker
+    assert_output "${CONTAINER_NAME}"
 }
 
 @test "container_is_running" {
     local CONTAINER_NAME=$(docker run --rm -d alpine sleep 100)
-    container_is_running "$CONTAINER_NAME"
-    docker rm -f "$CONTAINER_NAME"
-    ! container_is_running "$CONTAINER_NAME"
+    container_is_running "${CONTAINER_NAME}"
+    docker rm -f "${CONTAINER_NAME}"
+    ! container_is_running "${CONTAINER_NAME}"
 }
 
 @test "wait_for_smtp_port_in_container aborts wait after timeout" {
     local CONTAINER_NAME=$(docker run --rm -d alpine sleep 100)
     SECONDS=0
-    TEST_TIMEOUT_IN_SECONDS=2 run wait_for_smtp_port_in_container "$CONTAINER_NAME"
-    [[ $SECONDS -ge 2 ]]
+    TEST_TIMEOUT_IN_SECONDS=2 run wait_for_smtp_port_in_container "${CONTAINER_NAME}"
+    [[ ${SECONDS} -ge 2 ]]
     assert_failure
     assert_output --partial "Timed out on command"
 }
@@ -83,11 +83,11 @@ load 'test_helper/common'
 @test "wait_for_smtp_port_in_container returns immediately when port found" {
     local CONTAINER_NAME=$(docker run --rm -d alpine sh -c "sleep 10")
 
-    docker exec "$CONTAINER_NAME" apk add netcat-openbsd
-    docker exec "$CONTAINER_NAME" nc -l 25 &
+    docker exec "${CONTAINER_NAME}" apk add netcat-openbsd
+    docker exec "${CONTAINER_NAME}" nc -l 25 &
 
     SECONDS=0
-    TEST_TIMEOUT_IN_SECONDS=5 run wait_for_smtp_port_in_container "$CONTAINER_NAME"
-    [[ $SECONDS -lt 5 ]]
+    TEST_TIMEOUT_IN_SECONDS=5 run wait_for_smtp_port_in_container "${CONTAINER_NAME}"
+    [[ ${SECONDS} -lt 5 ]]
     assert_success
-}
\ No newline at end of file
+}
diff --git a/test/test_helper/common.bash b/test/test_helper/common.bash
index e65dd3ec..120f835d 100644
--- a/test/test_helper/common.bash
+++ b/test/test_helper/common.bash
@@ -1,7 +1,7 @@
 load 'test_helper/bats-support/load'
 load 'test_helper/bats-assert/load'
 
-NAME=tvial/docker-mailserver:testing
+# NAME=tvial/docker-mailserver:testing
 
 # default timeout is 120 seconds
 TEST_TIMEOUT_IN_SECONDS=${TEST_TIMEOUT_IN_SECONDS-120}
@@ -11,9 +11,9 @@ NUMBER_OF_LOG_LINES=${NUMBER_OF_LOG_LINES-10}
 # @param --fatal-test <command eval string> additional test whose failure aborts immediately
 # @param ... test to run
 function repeat_until_success_or_timeout {
-    local fatal_failure_test_command
+    local FATAL_FAILURE_TEST_COMMAND
     if [[ "${1}" == "--fatal-test" ]]; then
-        fatal_failure_test_command="${2}"
+        FATAL_FAILURE_TEST_COMMAND="${2}"
         shift 2
     fi
     if ! [[ "${1}" =~ ^[0-9]+$ ]]; then
@@ -25,8 +25,8 @@ function repeat_until_success_or_timeout {
     shift 1
     until "${@}"
     do
-        if [[ -n "${fatal_failure_test_command}" ]] && ! eval "${fatal_failure_test_command}"; then
-            echo "\`${fatal_failure_test_command}\` failed, early aborting repeat_until_success of \`${*}\`" >&2
+        if [[ -n "${FATAL_FAILURE_TEST_COMMAND}" ]] && ! eval "${FATAL_FAILURE_TEST_COMMAND}"; then
+            echo "\`${FATAL_FAILURE_TEST_COMMAND}\` failed, early aborting repeat_until_success of \`${*}\`" >&2
             return 1
         fi
         sleep 1
@@ -75,7 +75,7 @@ function container_is_running() {
 # @param ${1} port
 # @param ${2} container name
 function wait_for_tcp_port_in_container() {
-    repeat_until_success_or_timeout --fatal-test "container_is_running ${2}" "${TEST_TIMEOUT_IN_SECONDS}" docker exec ${2} /bin/sh -c "nc -z 0.0.0.0 ${1}"
+    repeat_until_success_or_timeout --fatal-test "container_is_running ${2}" "${TEST_TIMEOUT_IN_SECONDS}" docker exec "${2}" /bin/sh -c "nc -z 0.0.0.0 ${1}"
 }
 
 # @param ${1} name of the postfix container
@@ -90,13 +90,13 @@ function wait_for_amavis_port_in_container() {
 
 # @param ${1} name of the postfix container
 function wait_for_finished_setup_in_container() {
-    local status=0
-    repeat_until_success_or_timeout --fatal-test "container_is_running ${1}" "${TEST_TIMEOUT_IN_SECONDS}" sh -c "docker logs ${1} | grep 'is up and running'" || status=1
-    if [[ ${status} -eq 1 ]]; then
+    local STATUS=0
+    repeat_until_success_or_timeout --fatal-test "container_is_running ${1}" "${TEST_TIMEOUT_IN_SECONDS}" sh -c "docker logs ${1} | grep 'is up and running'" || STATUS=1
+    if [[ ${STATUS} -eq 1 ]]; then
         echo "Last ${NUMBER_OF_LOG_LINES} lines of container \`${1}\`'s log"
         docker logs "${1}" | tail -n "${NUMBER_OF_LOG_LINES}"
     fi
-    return ${status}
+    return ${STATUS}
 }
 
 SETUP_FILE_MARKER="${BATS_TMPDIR}/$(basename "${BATS_TEST_FILENAME}").setup_file"
@@ -177,6 +177,8 @@ function wait_for_service() {
 function wait_for_changes_to_be_detected_in_container() {
     local CONTAINER_NAME="${1}"
     local TIMEOUT=${TEST_TIMEOUT_IN_SECONDS}
-    repeat_in_container_until_success_or_timeout "${TIMEOUT}" "${CONTAINER_NAME}" \
+    repeat_in_container_until_success_or_timeout \
+        "${TIMEOUT}" \
+        "${CONTAINER_NAME}" \
         bash -c 'source /usr/local/bin/helper_functions.sh; cmp --silent -- <(_monitored_files_checksums) "${CHKSUM_FILE}"  >/dev/null'
 }