From 628e90223359534168ec9157637e09c78099edfd Mon Sep 17 00:00:00 2001
From: Casper <casperklein@users.noreply.github.com>
Date: Thu, 5 May 2022 10:28:38 +0200
Subject: [PATCH] Remove unnecessary quotes from command substitutions (#2561)

---
 Dockerfile                                    |  4 +-
 setup.sh                                      |  6 +--
 target/bin/addmailuser                        |  2 +-
 target/bin/updatemailuser                     |  2 +-
 target/scripts/check-for-changes.sh           |  2 +-
 target/scripts/helpers/dns.sh                 |  2 +-
 target/scripts/helpers/lock.sh                |  4 +-
 target/scripts/helpers/ssl.sh                 |  4 +-
 target/scripts/startup/daemons-stack.sh       |  2 +-
 target/scripts/startup/setup-stack.sh         |  4 +-
 test/default_relay_host.bats                  |  2 +-
 test/dovecot_inet_protocol.bats               |  2 +-
 test/helper-functions.bats                    |  2 +-
 test/linting/lint.sh                          | 10 ++---
 test/mail_changedetector.bats                 |  2 +-
 test/mail_disabled_clamav_spamassassin.bats   |  2 +-
 test/mail_dnsbl.bats                          |  2 +-
 test/mail_fail2ban.bats                       |  2 +-
 test/mail_fetchmail.bats                      |  2 +-
 test/mail_fetchmail_parallel.bats             |  2 +-
 test/mail_hostname.bats                       |  8 ++--
 test/mail_lmtp_ip.bats                        |  4 +-
 test/mail_pop3.bats                           |  2 +-
 test/mail_postfix_inet.bats                   |  8 ++--
 test/mail_postscreen.bats                     |  2 +-
 test/mail_privacy.bats                        |  2 +-
 test/mail_quotas_disabled.bats                |  2 +-
 test/mail_smtponly.bats                       |  2 +-
 test/mail_spam_junk_folder.bats               |  4 +-
 test/mail_special_use_folders.bats            |  2 +-
 test/mail_ssl_manual.bats                     |  2 +-
 test/mail_time.bats                           |  2 +-
 test/mail_tls_dhparams.bats                   | 14 +++----
 test/mail_undef_spam_subject.bats             |  4 +-
 test/mail_with_imap.bats                      |  2 +-
 test/mail_with_ldap.bats                      |  2 +-
 test/mail_with_mdbox.bats                     |  2 +-
 test/mail_with_postgrey.bats                  |  2 +-
 ...ail_with_postgrey_disabled_by_default.bats |  2 +-
 test/mail_with_sdbox.bats                     |  2 +-
 test/open_dkim.bats                           | 20 +++++-----
 test/permit_docker.bats                       |  4 +-
 test/security_tls_cipherlists.bats            |  2 +-
 test/test_helper.bats                         | 38 +++++++++----------
 test/test_helper/common.bash                  |  8 ++--
 test/tests.bats                               |  2 +-
 46 files changed, 102 insertions(+), 102 deletions(-)

diff --git a/Dockerfile b/Dockerfile
index d2c9e922..ad1b048f 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -69,9 +69,9 @@ RUN \
     --recv-keys ${FAIL2BAN_GPG_PUBLIC_KEY_ID} 2>&1 && \
   curl -Lkso fail2ban.deb ${FAIL2BAN_DEB_URL} && \
   curl -Lkso fail2ban.deb.asc ${FAIL2BAN_DEB_ASC_URL} && \
-  FINGERPRINT="$(LANG=C gpg --verify \
+  FINGERPRINT=$(LANG=C gpg --verify \
   fail2ban.deb.asc fail2ban.deb 2>&1 \
-    | sed -n 's#Primary key fingerprint: \(.*\)#\1#p')" && \
+    | sed -n 's#Primary key fingerprint: \(.*\)#\1#p') && \
   if [[ -z ${FINGERPRINT} ]]; then \
     echo "ERROR: Invalid GPG signature!" >&2; exit 1; fi && \
   if [[ ${FINGERPRINT} != "${FAIL2BAN_GPG_FINGERPRINT}" ]]; then \
diff --git a/setup.sh b/setup.sh
index 62dfd3e7..e0dd8aef 100755
--- a/setup.sh
+++ b/setup.sh
@@ -9,7 +9,7 @@ CONTAINER_NAME=
 CRI=
 DEFAULT_CONFIG_PATH=
 DESIRED_CONFIG_PATH=
-DIR="$(pwd)"
+DIR=$(pwd)
 DMS_CONFIG='/tmp/docker-mailserver'
 IMAGE_NAME=
 DEFAULT_IMAGE_NAME='docker.io/mailserver/docker-mailserver:latest'
@@ -90,10 +90,10 @@ function _get_absolute_script_directory
 {
   if dirname "$(readlink -f "${0}")" &>/dev/null
   then
-    DIR="$(dirname "$(readlink -f "${0}")")"
+    DIR=$(dirname "$(readlink -f "${0}")")
   elif realpath -e -L "${0}" &>/dev/null
   then
-    DIR="$(realpath -e -L "${0}")"
+    DIR=$(realpath -e -L "${0}")
     DIR="${DIR%/setup.sh}"
   fi
 }
diff --git a/target/bin/addmailuser b/target/bin/addmailuser
index 4882dbc8..069a0f57 100755
--- a/target/bin/addmailuser
+++ b/target/bin/addmailuser
@@ -56,7 +56,7 @@ then
   [[ -z ${PASSWD} ]] && _exit_with_error "Password must not be empty"
 fi
 
-HASH="$(doveadm pw -s SHA512-CRYPT -u "${FULL_EMAIL}" -p "${PASSWD}")"
+HASH=$(doveadm pw -s SHA512-CRYPT -u "${FULL_EMAIL}" -p "${PASSWD}")
 echo "${FULL_EMAIL}|${HASH}" >> "${DATABASE}"
 
 USER="${FULL_EMAIL%@*}"
diff --git a/target/bin/updatemailuser b/target/bin/updatemailuser
index f07d6f1e..d43999c4 100755
--- a/target/bin/updatemailuser
+++ b/target/bin/updatemailuser
@@ -25,7 +25,7 @@ then
   [[ -z ${PASSWD} ]] && _exit_with_error 'Password must not be empty'
 fi
 
-HASH="$(doveadm pw -s SHA512-CRYPT -u "${USER}" -p "${PASSWD}")"
+HASH=$(doveadm pw -s SHA512-CRYPT -u "${USER}" -p "${PASSWD}")
 
 touch "${DATABASE}"
 _create_lock # Protect config file with lock to avoid race conditions
diff --git a/target/scripts/check-for-changes.sh b/target/scripts/check-for-changes.sh
index daeaf590..9d0b8ff4 100755
--- a/target/scripts/check-for-changes.sh
+++ b/target/scripts/check-for-changes.sh
@@ -94,7 +94,7 @@ function _check_for_changes
 
       # Prevent an unnecessary change detection from the newly extracted cert files by updating their hashes in advance:
       local CERT_DOMAIN
-      CERT_DOMAIN="$(_find_letsencrypt_domain)"
+      CERT_DOMAIN=$(_find_letsencrypt_domain)
       ACME_CERT_DIR="/etc/letsencrypt/live/${CERT_DOMAIN}"
 
       sed -i "\|${ACME_CERT_DIR}|d" "${CHKSUM_FILE}.new"
diff --git a/target/scripts/helpers/dns.sh b/target/scripts/helpers/dns.sh
index 2237c601..d47ab204 100644
--- a/target/scripts/helpers/dns.sh
+++ b/target/scripts/helpers/dns.sh
@@ -52,7 +52,7 @@ function _obtain_hostname_and_domainname
       # going forward. In future our docs should drop any mention of it.
 
       #shellcheck disable=SC2034
-      DOMAINNAME="$(hostname -d)"
+      DOMAINNAME=$(hostname -d)
     fi
   fi
 
diff --git a/target/scripts/helpers/lock.sh b/target/scripts/helpers/lock.sh
index a8fef039..80e74aa0 100644
--- a/target/scripts/helpers/lock.sh
+++ b/target/scripts/helpers/lock.sh
@@ -2,10 +2,10 @@
 
 # This becomes the sourcing script name
 # (example: check-for-changes.sh)
-SCRIPT_NAME="$(basename "$0")"
+SCRIPT_NAME=$(basename "$0")
 # Used inside of lock files to identify them and
 # prevent removal by other instances of docker-mailserver
-LOCK_ID="$(uuid)"
+LOCK_ID=$(uuid)
 
 function _create_lock
 {
diff --git a/target/scripts/helpers/ssl.sh b/target/scripts/helpers/ssl.sh
index daca4b6d..28a907b8 100644
--- a/target/scripts/helpers/ssl.sh
+++ b/target/scripts/helpers/ssl.sh
@@ -187,8 +187,8 @@ function _setup_ssl
 
       # checks folders in /etc/letsencrypt/live to identify which one to implicitly use:
       local LETSENCRYPT_DOMAIN LETSENCRYPT_KEY
-      LETSENCRYPT_DOMAIN="$(_find_letsencrypt_domain)"
-      LETSENCRYPT_KEY="$(_find_letsencrypt_key "${LETSENCRYPT_DOMAIN}")"
+      LETSENCRYPT_DOMAIN=$(_find_letsencrypt_domain)
+      LETSENCRYPT_KEY=$(_find_letsencrypt_key "${LETSENCRYPT_DOMAIN}")
 
       # Update relevant config for Postfix and Dovecot
       _log 'trace' "Adding ${LETSENCRYPT_DOMAIN} SSL certificate to the postfix and dovecot configuration"
diff --git a/target/scripts/startup/daemons-stack.sh b/target/scripts/startup/daemons-stack.sh
index cdfcbd82..8215ff83 100644
--- a/target/scripts/startup/daemons-stack.sh
+++ b/target/scripts/startup/daemons-stack.sh
@@ -15,7 +15,7 @@ function _default_start_daemon
   _log 'debug' "Starting ${1:?}"
 
   local RESULT
-  RESULT="$(supervisorctl start "${1}" 2>&1)"
+  RESULT=$(supervisorctl start "${1}" 2>&1)
 
   # shellcheck disable=SC2181
   if [[ ${?} -ne 0 ]]
diff --git a/target/scripts/startup/setup-stack.sh b/target/scripts/startup/setup-stack.sh
index 21607296..d6e7159d 100644
--- a/target/scripts/startup/setup-stack.sh
+++ b/target/scripts/startup/setup-stack.sh
@@ -714,7 +714,7 @@ function _setup_docker_permit
 
   CONTAINER_IP=$(ip addr show "${NETWORK_INTERFACE}" | \
     grep 'inet ' | sed 's|[^0-9\.\/]*||g' | cut -d '/' -f 1)
-  CONTAINER_NETWORK="$(echo "${CONTAINER_IP}" | cut -d '.' -f1-2).0.0"
+  CONTAINER_NETWORK=$(echo "${CONTAINER_IP}" | cut -d '.' -f1-2).0.0
 
   if [[ -z ${CONTAINER_IP} ]]
   then
@@ -955,7 +955,7 @@ function _setup_security_stack
       cat >"${SPAMASSASSIN_KAM_CRON_FILE}" <<"EOM"
 #! /bin/bash
 
-RESULT="$(sa-update --gpgkey 24C063D8 --channel kam.sa-channels.mcgrail.com 2>&1)"
+RESULT=$(sa-update --gpgkey 24C063D8 --channel kam.sa-channels.mcgrail.com 2>&1)
 EXIT_CODE=${?}
 
 # see https://spamassassin.apache.org/full/3.1.x/doc/sa-update.html#exit_codes
diff --git a/test/default_relay_host.bats b/test/default_relay_host.bats
index ee38d529..be8008c2 100644
--- a/test/default_relay_host.bats
+++ b/test/default_relay_host.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup() {
 	local PRIVATE_CONFIG
- 	PRIVATE_CONFIG="$(duplicate_config_for_container relay-hosts)"
+ 	PRIVATE_CONFIG=$(duplicate_config_for_container relay-hosts)
     docker run -d --name mail_with_default_relay \
 		-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 		-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/dovecot_inet_protocol.bats b/test/dovecot_inet_protocol.bats
index 7b0c21cd..dfb63c8b 100644
--- a/test/dovecot_inet_protocol.bats
+++ b/test/dovecot_inet_protocol.bats
@@ -4,7 +4,7 @@ function setup_file() {
   local PRIVATE_CONFIG
   export ALL IPV4 IPV6
 
-  PRIVATE_CONFIG="$(duplicate_config_for_container . "${IPV4}")"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . "${IPV4}")
   ALL="mail_dovecot_all_protocols"
   IPV4="mail_dovecot_ipv4"
   IPV6="mail_dovecot_ipv6"
diff --git a/test/helper-functions.bats b/test/helper-functions.bats
index bd48c1d4..2145a1d7 100644
--- a/test/helper-functions.bats
+++ b/test/helper-functions.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_helper_functions \
         --cap-add=NET_ADMIN \
         -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
diff --git a/test/linting/lint.sh b/test/linting/lint.sh
index c7e125f8..191313c2 100755
--- a/test/linting/lint.sh
+++ b/test/linting/lint.sh
@@ -7,7 +7,7 @@
 SCRIPT="lint.sh"
 
 SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
-REPO_ROOT="$(realpath "${SCRIPT_DIR}"/../../)"
+REPO_ROOT=$(realpath "${SCRIPT_DIR}"/../../)
 
 HADOLINT_VERSION=2.8.0
 ECLINT_VERSION=2.3.5
@@ -93,14 +93,14 @@ function _shellcheck
   local SCRIPT='SHELLCHECK'
 
   # File paths for shellcheck:
-  F_SH="$(find . -type f -iname '*.sh' \
+  F_SH=$(find . -type f -iname '*.sh' \
     -not -path './test/bats/*' \
     -not -path './test/test_helper/*' \
     -not -path './target/docker-configomat/*'
-  )"
+  )
   # shellcheck disable=SC2248
-  F_BIN="$(find 'target/bin' -type f -not -name '*.py')"
-  F_BATS="$(find 'test' -maxdepth 1 -type f -iname '*.bats')"
+  F_BIN=$(find 'target/bin' -type f -not -name '*.py')
+  F_BATS=$(find 'test' -maxdepth 1 -type f -iname '*.bats')
 
   # This command is a bit easier to grok as multi-line.
   # There is a `.shellcheckrc` file, but it's only supports half of the options below, thus kept as CLI:
diff --git a/test/mail_changedetector.bats b/test/mail_changedetector.bats
index 536c28e2..7e6f73dc 100644
--- a/test/mail_changedetector.bats
+++ b/test/mail_changedetector.bats
@@ -6,7 +6,7 @@ load 'test_helper/common'
 
 function setup_file() {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . mail_changedetector_one)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . mail_changedetector_one)
 
   docker run -d --name mail_changedetector_one \
   -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
diff --git a/test/mail_disabled_clamav_spamassassin.bats b/test/mail_disabled_clamav_spamassassin.bats
index 37018357..79190462 100644
--- a/test/mail_disabled_clamav_spamassassin.bats
+++ b/test/mail_disabled_clamav_spamassassin.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run --rm -d --name mail_disabled_clamav_spamassassin \
 		  -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 		  -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_dnsbl.bats b/test/mail_dnsbl.bats
index 08d6ad51..c1043154 100644
--- a/test/mail_dnsbl.bats
+++ b/test/mail_dnsbl.bats
@@ -5,7 +5,7 @@ CONTAINER2="mail_dnsbl_disabled"
 
 function setup_file() {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . "${CONTAINER}")"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . "${CONTAINER}")
 
 	docker run --rm -d --name "${CONTAINER}" \
 		-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
diff --git a/test/mail_fail2ban.bats b/test/mail_fail2ban.bats
index 44768c68..fa5ce29f 100644
--- a/test/mail_fail2ban.bats
+++ b/test/mail_fail2ban.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run --rm -d --name mail_fail2ban \
 		-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 		-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_fetchmail.bats b/test/mail_fetchmail.bats
index 49aa7e6c..07f2fb07 100644
--- a/test/mail_fetchmail.bats
+++ b/test/mail_fetchmail.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_fetchmail \
 		-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 		-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_fetchmail_parallel.bats b/test/mail_fetchmail_parallel.bats
index dec6f4a3..a1d87d86 100644
--- a/test/mail_fetchmail_parallel.bats
+++ b/test/mail_fetchmail_parallel.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_fetchmail_parallel \
 		-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 		-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_hostname.bats b/test/mail_hostname.bats
index 1cf135b7..caa5b08f 100644
--- a/test/mail_hostname.bats
+++ b/test/mail_hostname.bats
@@ -3,7 +3,7 @@ load 'test_helper/common'
 
 function setup_file() {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . mail_override_hostname)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . mail_override_hostname)
 	docker run --rm -d --name mail_override_hostname \
 		-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 		-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -13,7 +13,7 @@ function setup_file() {
 		-h unknown.domain.tld \
 		-t "${NAME}"
 
-  PRIVATE_CONFIG_TWO="$(duplicate_config_for_container . mail_non_subdomain_hostname)"
+  PRIVATE_CONFIG_TWO=$(duplicate_config_for_container . mail_non_subdomain_hostname)
 	docker run --rm -d --name mail_non_subdomain_hostname \
 		-v "${PRIVATE_CONFIG_TWO}":/tmp/docker-mailserver \
 		-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -23,7 +23,7 @@ function setup_file() {
     --domainname domain.com \
 		-t "${NAME}"
 
-  PRIVATE_CONFIG_THREE="$(duplicate_config_for_container . mail_srs_domainname)"
+  PRIVATE_CONFIG_THREE=$(duplicate_config_for_container . mail_srs_domainname)
   docker run --rm -d --name mail_srs_domainname \
     -v "${PRIVATE_CONFIG_THREE}":/tmp/docker-mailserver \
     -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -34,7 +34,7 @@ function setup_file() {
     --hostname 'mail' \
     -t "${NAME}"
 
-  PRIVATE_CONFIG_FOUR="$(duplicate_config_for_container . mail_domainname)"
+  PRIVATE_CONFIG_FOUR=$(duplicate_config_for_container . mail_domainname)
   docker run --rm -d --name mail_domainname \
     -v "${PRIVATE_CONFIG_FOUR}":/tmp/docker-mailserver \
     -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_lmtp_ip.bats b/test/mail_lmtp_ip.bats
index 8b95dadd..341bd553 100644
--- a/test/mail_lmtp_ip.bats
+++ b/test/mail_lmtp_ip.bats
@@ -2,8 +2,8 @@ load 'test_helper/common'
 
 setup_file() {
     local PRIVATE_CONFIG PRIVATE_ETC
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
-    PRIVATE_ETC="$(duplicate_config_for_container dovecot-lmtp/ mail_lmtp_ip_dovecot-lmtp)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
+    PRIVATE_ETC=$(duplicate_config_for_container dovecot-lmtp/ mail_lmtp_ip_dovecot-lmtp)
     docker run -d --name mail_lmtp_ip \
     -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
     -v "${PRIVATE_ETC}":/etc/dovecot \
diff --git a/test/mail_pop3.bats b/test/mail_pop3.bats
index 93f8a3ae..fb397658 100644
--- a/test/mail_pop3.bats
+++ b/test/mail_pop3.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_pop3 \
     -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
     -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_postfix_inet.bats b/test/mail_postfix_inet.bats
index 14977e0a..3f90b735 100644
--- a/test/mail_postfix_inet.bats
+++ b/test/mail_postfix_inet.bats
@@ -6,7 +6,7 @@ load 'test_helper/common'
 
 @test "checking postfix: inet default" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . )"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . )
   docker run -d --name mail_postfix_inet_default \
             -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
             -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -23,7 +23,7 @@ load 'test_helper/common'
 
 @test "checking postfix: inet all" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . )"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . )
   docker run -d --name mail_postfix_inet_all \
             -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
             -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -41,7 +41,7 @@ load 'test_helper/common'
 
 @test "checking postfix: inet ipv4" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . )"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . )
   docker run -d --name mail_postfix_inet_ipv4 \
 		-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 		-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -59,7 +59,7 @@ load 'test_helper/common'
 
 @test "checking postfix: inet ipv6" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . )"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . )
   docker run -d --name mail_postfix_inet_ipv6 \
             -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
             -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_postscreen.bats b/test/mail_postscreen.bats
index 3c25d14b..166f4d38 100644
--- a/test/mail_postscreen.bats
+++ b/test/mail_postscreen.bats
@@ -7,7 +7,7 @@ setup() {
 
 setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_postscreen \
               -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
               -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_privacy.bats b/test/mail_privacy.bats
index d21c0dfc..a09a3f32 100644
--- a/test/mail_privacy.bats
+++ b/test/mail_privacy.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup_file() {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container .)
   docker run -d --name mail_privacy \
     -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
     -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_quotas_disabled.bats b/test/mail_quotas_disabled.bats
index 56cedad5..27577178 100644
--- a/test/mail_quotas_disabled.bats
+++ b/test/mail_quotas_disabled.bats
@@ -7,7 +7,7 @@ load 'test_helper/common'
 
 function setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_no_quotas \
               -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
               -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_smtponly.bats b/test/mail_smtponly.bats
index 62990345..083a4245 100644
--- a/test/mail_smtponly.bats
+++ b/test/mail_smtponly.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run --rm -d --name mail_smtponly \
               -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
               -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_spam_junk_folder.bats b/test/mail_spam_junk_folder.bats
index 6f0fd03e..23d64c8e 100644
--- a/test/mail_spam_junk_folder.bats
+++ b/test/mail_spam_junk_folder.bats
@@ -6,7 +6,7 @@ load 'test_helper/common'
 
 @test "checking amavis: spam message is delivered and moved to the Junk folder (MOVE_SPAM_TO_JUNK=1)" {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_spam_moved_junk)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_spam_moved_junk)
     docker run -d --name mail_spam_moved_junk \
               -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
               -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -35,7 +35,7 @@ load 'test_helper/common'
 
 @test "checking amavis: spam message is delivered to INBOX (MOVE_SPAM_TO_JUNK=0)" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . mail_spam_moved_new)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . mail_spam_moved_new)
   docker run -d --name mail_spam_moved_new \
             -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
             -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_special_use_folders.bats b/test/mail_special_use_folders.bats
index 9cdf21b4..7c141c71 100644
--- a/test/mail_special_use_folders.bats
+++ b/test/mail_special_use_folders.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_special_use_folders \
                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                 -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_ssl_manual.bats b/test/mail_ssl_manual.bats
index 9171494a..81e326a0 100644
--- a/test/mail_ssl_manual.bats
+++ b/test/mail_ssl_manual.bats
@@ -16,7 +16,7 @@ function setup_file() {
 
     local PRIVATE_CONFIG
     export DOMAIN_SSL_MANUAL='example.test'
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
 
     docker run -d --name mail_manual_ssl \
         --volume "${PRIVATE_CONFIG}/:/tmp/docker-mailserver/" \
diff --git a/test/mail_time.bats b/test/mail_time.bats
index 4fb5e9bc..52407a59 100644
--- a/test/mail_time.bats
+++ b/test/mail_time.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 setup_file() {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container .)
 
   docker run -d --name mail_time \
     -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
diff --git a/test/mail_tls_dhparams.bats b/test/mail_tls_dhparams.bats
index 12f53994..05e5f608 100644
--- a/test/mail_tls_dhparams.bats
+++ b/test/mail_tls_dhparams.bats
@@ -35,10 +35,10 @@ function setup_file() {
 
 
   DH_DEFAULT_PARAMS="$(pwd)/target/shared/ffdhe4096.pem"
-  DH_DEFAULT_CHECKSUM="$(sha512sum "${DH_DEFAULT_PARAMS}" | awk '{print $1}')"
+  DH_DEFAULT_CHECKSUM=$(sha512sum "${DH_DEFAULT_PARAMS}" | awk '{print $1}')
 
   DH_CUSTOM_PARAMS="$(pwd)/test/test-files/ssl/custom-dhe-params.pem"
-  DH_CUSTOM_CHECKSUM="$(sha512sum "${DH_CUSTOM_PARAMS}" | awk '{print $1}')"
+  DH_CUSTOM_CHECKSUM=$(sha512sum "${DH_CUSTOM_PARAMS}" | awk '{print $1}')
 }
 
 # Not used
@@ -54,12 +54,12 @@ function setup_file() {
 
     # Verify the FFDHE params file has not been modified (equivalent to `target/shared/ffdhe4096.pem.sha512sum`):
     local DH_MOZILLA_CHECKSUM
-    DH_MOZILLA_CHECKSUM="$(curl https://ssl-config.mozilla.org/ffdhe4096.txt -s | sha512sum | awk '{print $1}')"
+    DH_MOZILLA_CHECKSUM=$(curl https://ssl-config.mozilla.org/ffdhe4096.txt -s | sha512sum | awk '{print $1}')
     assert_equal "${DH_DEFAULT_CHECKSUM}" "${DH_MOZILLA_CHECKSUM}"
 }
 
 @test "testing tls: DH Parameters - Default [ONE_DIR=0]" {
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_dhparams_default_0)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_dhparams_default_0)
     DMS_ONE_DIR=0
 
     common_container_setup
@@ -67,14 +67,14 @@ function setup_file() {
 }
 
 @test "testing tls: DH Parameters - Default [ONE_DIR=1]" {
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_dhparams_default_1)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_dhparams_default_1)
 
     common_container_setup
     should_have_valid_checksum "${DH_DEFAULT_CHECKSUM}"
 }
 
 @test "testing tls: DH Parameters - Custom [ONE_DIR=0]" {
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_dhparams_custom_0)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_dhparams_custom_0)
     # shellcheck disable=SC2030
     DMS_ONE_DIR=0
 
@@ -87,7 +87,7 @@ function setup_file() {
 
 @test "testing tls: DH Parameters - Custom [ONE_DIR=1]" {
     # shellcheck disable=SC2030
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_dhparams_custom_1)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_dhparams_custom_1)
 
     cp "${DH_CUSTOM_PARAMS}" "${PRIVATE_CONFIG}/dhparams.pem"
 
diff --git a/test/mail_undef_spam_subject.bats b/test/mail_undef_spam_subject.bats
index 31728965..4f44ebfd 100644
--- a/test/mail_undef_spam_subject.bats
+++ b/test/mail_undef_spam_subject.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_undef_spam_subject \
             -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
             -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -10,7 +10,7 @@ function setup() {
             -e SA_SPAM_SUBJECT="undef" \
             -h mail.my-domain.com -t "${NAME}"
 
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_undef_spam_subject_2)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_undef_spam_subject_2)
     CONTAINER=$(docker run -d \
                           -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                           -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_with_imap.bats b/test/mail_with_imap.bats
index 04ce3052..74ae5cd6 100644
--- a/test/mail_with_imap.bats
+++ b/test/mail_with_imap.bats
@@ -3,7 +3,7 @@ load 'test_helper/common'
 
 setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_with_imap \
     -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
     -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_with_ldap.bats b/test/mail_with_ldap.bats
index 5f8a6b50..137ecf17 100644
--- a/test/mail_with_ldap.bats
+++ b/test/mail_with_ldap.bats
@@ -25,7 +25,7 @@ function setup_file() {
 
   # _setup_ldap uses configomat with .ext files and ENV vars like DOVECOT_TLS with a prefix (eg DOVECOT_ or LDAP_)
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container .)
   docker run -d --name mail_with_ldap \
     -v "${PRIVATE_CONFIG}:/tmp/docker-mailserver" \
     -v "$(pwd)/test/test-files:/tmp/docker-mailserver-test:ro" \
diff --git a/test/mail_with_mdbox.bats b/test/mail_with_mdbox.bats
index d0925879..a607f35a 100644
--- a/test/mail_with_mdbox.bats
+++ b/test/mail_with_mdbox.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_with_mdbox_format \
                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                 -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_with_postgrey.bats b/test/mail_with_postgrey.bats
index d81c38d1..660a508a 100644
--- a/test/mail_with_postgrey.bats
+++ b/test/mail_with_postgrey.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_with_postgrey \
               -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
               -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_with_postgrey_disabled_by_default.bats b/test/mail_with_postgrey_disabled_by_default.bats
index 28249544..23c5e6da 100644
--- a/test/mail_with_postgrey_disabled_by_default.bats
+++ b/test/mail_with_postgrey_disabled_by_default.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 function setup() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     CONTAINER=$(docker run -d \
                           -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                           -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/mail_with_sdbox.bats b/test/mail_with_sdbox.bats
index 696ecbca..6167daae 100644
--- a/test/mail_with_sdbox.bats
+++ b/test/mail_with_sdbox.bats
@@ -2,7 +2,7 @@ load 'test_helper/common'
 
 setup_file() {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     docker run -d --name mail_with_sdbox_format \
                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                 -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/open_dkim.bats b/test/open_dkim.bats
index d8937032..e4fc3616 100644
--- a/test/open_dkim.bats
+++ b/test/open_dkim.bats
@@ -10,7 +10,7 @@ TEST_FILE='checking OpenDKIM: '
 function setup_file
 {
 	local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . "${CONTAINER_NAME}")"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . "${CONTAINER_NAME}")
 
   docker run -d \
     --name "${CONTAINER_NAME}" \
@@ -62,7 +62,7 @@ function teardown_file
 # TODO Needs complete re-write
 @test "${TEST_FILE}generator creates default keys size" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . mail_default_key_size)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . mail_default_key_size)
 
   # Prepare default key size 4096
   rm -rf "${PRIVATE_CONFIG}/keyDefault"
@@ -93,7 +93,7 @@ function teardown_file
 # TODO Needs complete re-write
 @test "${TEST_FILE}generator creates key size 4096" {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_key_size_4096)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_key_size_4096)
 
     rm -rf "${PRIVATE_CONFIG}/key4096"
     mkdir -p "${PRIVATE_CONFIG}/config/key4096"
@@ -122,7 +122,7 @@ function teardown_file
 # TODO Needs complete re-write
 @test "${TEST_FILE}generator creates key size 2048" {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_key_size_2048)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_key_size_2048)
 
     rm -rf "${PRIVATE_CONFIG}/key2048"
     mkdir -p "${PRIVATE_CONFIG}/config/key2048"
@@ -151,7 +151,7 @@ function teardown_file
 # TODO Needs complete re-write
 @test "${TEST_FILE}generator creates key size 1024" {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container . mail_key_size_1024)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container . mail_key_size_1024)
 
     rm -rf "${PRIVATE_CONFIG}/key1024"
     mkdir -p "${PRIVATE_CONFIG}/key1024"
@@ -176,7 +176,7 @@ function teardown_file
 
 @test "${TEST_FILE}generator creates keys, tables and TrustedHosts" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . mail_dkim_generator_creates_keys_tables_TrustedHosts)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . mail_dkim_generator_creates_keys_tables_TrustedHosts)
   rm -rf "${PRIVATE_CONFIG}/empty"
   mkdir -p "${PRIVATE_CONFIG}/empty"
   run docker run --rm \
@@ -212,7 +212,7 @@ function teardown_file
 
 @test "${TEST_FILE}generator creates keys, tables and TrustedHosts without postfix-accounts.cf" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . )"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . )
   rm -rf "${PRIVATE_CONFIG}/without-accounts"
   mkdir -p "${PRIVATE_CONFIG}/without-accounts"
   run docker run --rm \
@@ -248,7 +248,7 @@ function teardown_file
 
 @test "${TEST_FILE}generator creates keys, tables and TrustedHosts without postfix-virtual.cf" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . "${BATS_TEST_NAME}")"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . "${BATS_TEST_NAME}")
   rm -rf "${PRIVATE_CONFIG}/without-virtual"
   mkdir -p "${PRIVATE_CONFIG}/without-virtual"
   run docker run --rm \
@@ -286,7 +286,7 @@ function teardown_file
 
 @test "${TEST_FILE}generator creates keys, tables and TrustedHosts using manual provided domain name" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . "${BATS_TEST_NAME}")"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . "${BATS_TEST_NAME}")
   rm -rf "${PRIVATE_CONFIG}/with-domain" && mkdir -p "${PRIVATE_CONFIG}/with-domain"
 
   # generate first key
@@ -374,7 +374,7 @@ function teardown_file
 
 @test "${TEST_FILE}generator creates keys, tables and TrustedHosts using manual provided selector name" {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . "${BATS_TEST_NAME}")"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . "${BATS_TEST_NAME}")
   rm -rf "${PRIVATE_CONFIG}/with-selector" && mkdir -p "${PRIVATE_CONFIG}/with-selector"
 
   # Generate first key
diff --git a/test/permit_docker.bats b/test/permit_docker.bats
index ef7fb1b5..5ba4d9fb 100644
--- a/test/permit_docker.bats
+++ b/test/permit_docker.bats
@@ -8,7 +8,7 @@ setup_file() {
 	# currently we cannot use --network in `docker run` multiple times, it will just use the last one
 	# instead we need to use create, network connect and start (see https://success.docker.com/article/multiple-docker-networks)
 	local PRIVATE_CONFIG
-  	PRIVATE_CONFIG="$(duplicate_config_for_container . mail_smtponly_second_network)"
+  	PRIVATE_CONFIG=$(duplicate_config_for_container . mail_smtponly_second_network)
 	docker create --name mail_smtponly_second_network \
 					-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 					-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
@@ -19,7 +19,7 @@ setup_file() {
 					-t "${NAME}"
 	docker network connect "${NON_DEFAULT_DOCKER_MAIL_NETWORK_NAME}2" mail_smtponly_second_network
 	docker start mail_smtponly_second_network
-	PRIVATE_CONFIG="$(duplicate_config_for_container . mail_smtponly_second_network_sender)"
+	PRIVATE_CONFIG=$(duplicate_config_for_container . mail_smtponly_second_network_sender)
 	docker run -d --name mail_smtponly_second_network_sender \
 				-v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
 				-v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
diff --git a/test/security_tls_cipherlists.bats b/test/security_tls_cipherlists.bats
index fabe1a03..5c2b3b45 100644
--- a/test/security_tls_cipherlists.bats
+++ b/test/security_tls_cipherlists.bats
@@ -23,7 +23,7 @@ function setup_file() {
     # Copies all of `./test/config/` to specific directory for testing
     # `${PRIVATE_CONFIG}` becomes `$(pwd)/test/duplicate_configs/<bats test filename>`
     export PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
 
     # Pull `testssl.sh` image in advance to avoid it interfering with the `run` captured output.
     # Only interferes (potential test failure) with `assert_output` not `assert_success`?
diff --git a/test/test_helper.bats b/test/test_helper.bats
index 86317652..57d54967 100644
--- a/test/test_helper.bats
+++ b/test/test_helper.bats
@@ -99,11 +99,11 @@ load 'test_helper/common'
 @test "wait_for_finished_setup_in_container" {
     # variable not local to make visible to teardown
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
-    CONTAINER_NAME="$(docker run -d --rm \
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
+    CONTAINER_NAME=$(docker run -d --rm \
                                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                                 -h mail.my-domain.com \
-                                -t "${NAME}")"
+                                -t "${NAME}")
     teardown() { docker rm -f "${CONTAINER_NAME}"; }
 
     # the setup should not be finished immediately after starting
@@ -117,7 +117,7 @@ load 'test_helper/common'
 
 @test "duplicate_config_for_container" {
     local path
-    path="$(duplicate_config_for_container duplicate_config_test)"
+    path=$(duplicate_config_for_container duplicate_config_test)
 
     run cat "${path}/marker"
     assert_line "This marker file is there to identify the correct config being copied"
@@ -128,12 +128,12 @@ load 'test_helper/common'
 
 @test "container_has_service_running/wait_for_service" {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     # variable not local to make visible to teardown
-    CONTAINER_NAME="$(docker run -d --rm \
+    CONTAINER_NAME=$(docker run -d --rm \
                                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                                 -h mail.my-domain.com \
-                                -t "${NAME}")"
+                                -t "${NAME}")
     teardown() { docker rm -f "${CONTAINER_NAME}"; }
 
     # pick a service that was not started
@@ -154,12 +154,12 @@ load 'test_helper/common'
 
 @test "wait_for_changes_to_be_detected_in_container fails when timeout is reached" {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     # variable not local to make visible to teardown
-    CONTAINER_NAME="$(docker run -d --rm \
+    CONTAINER_NAME=$(docker run -d --rm \
                                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                                 -h mail.my-domain.com \
-                                -t "${NAME}")"
+                                -t "${NAME}")
     teardown() { docker rm -f "${CONTAINER_NAME}"; }
 
     # wait for the initial checksum detection to complete
@@ -177,12 +177,12 @@ load 'test_helper/common'
 
 @test "wait_for_changes_to_be_detected_in_container succeeds within timeout" {
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     # variable not local to make visible to teardown
-    CONTAINER_NAME="$(docker run -d --rm \
+    CONTAINER_NAME=$(docker run -d --rm \
                                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                                 -h mail.my-domain.com \
-                                -t "${NAME}")"
+                                -t "${NAME}")
     teardown() { docker rm -f "${CONTAINER_NAME}"; }
 
     # wait for the initial checksum detection to complete
@@ -202,15 +202,15 @@ load 'test_helper/common'
     skip 'disabled as it fails randomly: https://github.com/docker-mailserver/docker-mailserver/pull/2177'
 
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     # variable not local to make visible to teardown
     # enable ClamAV to make message delivery slower, so we can detect it
-    CONTAINER_NAME="$(docker run -d --rm \
+    CONTAINER_NAME=$(docker run -d --rm \
                                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                                 -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
                                 -e ENABLE_CLAMAV=1 \
                                 -h mail.my-domain.com \
-                                -t "${NAME}")"
+                                -t "${NAME}")
 
     teardown() { docker rm -f "${CONTAINER_NAME}"; }
 
@@ -233,15 +233,15 @@ load 'test_helper/common'
     skip 'disabled as it fails randomly: https://github.com/docker-mailserver/docker-mailserver/pull/2177'
 
     local PRIVATE_CONFIG
-    PRIVATE_CONFIG="$(duplicate_config_for_container .)"
+    PRIVATE_CONFIG=$(duplicate_config_for_container .)
     # variable not local to make visible to teardown
     # enable ClamAV to make message delivery slower, so we can detect it
-    CONTAINER_NAME="$(docker run -d --rm \
+    CONTAINER_NAME=$(docker run -d --rm \
                                 -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \
                                 -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
                                 -e ENABLE_CLAMAV=1 \
                                 -h mail.my-domain.com \
-                                -t "${NAME}")"
+                                -t "${NAME}")
 
     teardown() { docker rm -f "${CONTAINER_NAME}"; }
 
diff --git a/test/test_helper/common.bash b/test/test_helper/common.bash
index 72497276..514a387f 100644
--- a/test/test_helper/common.bash
+++ b/test/test_helper/common.bash
@@ -128,7 +128,7 @@ function private_config_path() {
 # @return path to the folder where the config is duplicated
 function duplicate_config_for_container() {
     local OUTPUT_FOLDER
-    OUTPUT_FOLDER="$(private_config_path "${2}")"  || return $?
+    OUTPUT_FOLDER=$(private_config_path "${2}")  || return $?
     rm -rf "${OUTPUT_FOLDER:?}/" || return $? # cleanup
     mkdir -p "${OUTPUT_FOLDER}" || return $?
     cp -r "${PWD}/test/config/${1:?}/." "${OUTPUT_FOLDER}" || return $?
@@ -169,16 +169,16 @@ function wait_for_empty_mail_queue_in_container() {
 # For individual test override the var via `local` var instead.
 #
 # For example, if you need an immutable config volume that can't be affected by other tests
-# in the file, then use `local TEST_TMP_CONFIG="$(duplicate_config_for_container . "${UNIQUE_ID_HERE}")"`
+# in the file, then use `local TEST_TMP_CONFIG=$(duplicate_config_for_container . "${UNIQUE_ID_HERE}")`
 function init_with_defaults() {
   export TEST_NAME TEST_TMP_CONFIG
 
   # In `setup_file()` the default name to use for the currently tested docker container
   # is `${TEST_NAME}` global defined here. It derives the name from the test filename:
   # `basename` to ignore absolute dir path and file extension, only extract filename.
-  TEST_NAME="$(basename "${BATS_TEST_FILENAME}" '.bats')"
+  TEST_NAME=$(basename "${BATS_TEST_FILENAME}" '.bats')
   # In `setup_file()` creates a single copy of the test config folder to use for an entire test file:
-  TEST_TMP_CONFIG="$(duplicate_config_for_container . "${TEST_NAME}")"
+  TEST_TMP_CONFIG=$(duplicate_config_for_container . "${TEST_NAME}")
 
   # Common complimentary test files, read-only safe to share across containers:
   export TEST_FILES_CONTAINER_PATH='/tmp/docker-mailserver-test'
diff --git a/test/tests.bats b/test/tests.bats
index 38a34e8d..0766e2a3 100644
--- a/test/tests.bats
+++ b/test/tests.bats
@@ -7,7 +7,7 @@ IMAGE_NAME="${NAME}"
 
 setup_file() {
   local PRIVATE_CONFIG
-  PRIVATE_CONFIG="$(duplicate_config_for_container . mail)"
+  PRIVATE_CONFIG=$(duplicate_config_for_container . mail)
   mv "${PRIVATE_CONFIG}/user-patches/user-patches.sh" "${PRIVATE_CONFIG}/user-patches.sh"
   docker run --rm -d --name mail \
     -v "${PRIVATE_CONFIG}":/tmp/docker-mailserver \