diff --git a/docker-bench-security.sh b/docker-bench-security.sh
index dc2ba9e..2b2ad1a 100755
--- a/docker-bench-security.sh
+++ b/docker-bench-security.sh
@@ -25,8 +25,7 @@ for p in $req_progs; do
 done
 
 # Ensure we can connect to docker daemon
-docker ps -q >/dev/null 2>&1
-if [ $? -ne 0 ]; then
+if ! docker ps -q >/dev/null 2>&1; then
   printf "Error connecting to docker daemon (does docker ps work?)\n"
   exit 1
 fi
@@ -81,8 +80,10 @@ main () {
   # If there is a container with label docker_bench_security, memorize it:
   benchcont="nil"
   for c in $containers; do
-    labels=$(docker inspect --format '{{ .Config.Labels }}' "$c")
-    contains "$labels" "docker_bench_security" && benchcont="$c"
+    if docker inspect --format '{{ .Config.Labels }}' "$c" | \
+     grep -e 'docker.bench.security' >/dev/null 2>&1; then
+      benchcont="$c"
+    fi
   done
   # List all running containers except docker-bench (use names to improve readability in logs)
   containers=$(docker ps | sed '1d' |  awk '{print $NF}' | grep -v "$benchcont")
diff --git a/helper_lib.sh b/helper_lib.sh
index 8b4a635..df48084 100644
--- a/helper_lib.sh
+++ b/helper_lib.sh
@@ -25,18 +25,6 @@ do_version_check() {
     fi
 }
 
-# Compares two strings and returns 0 if the second is a substring of the first
-contains() {
-    string="$1"
-    substring="$2"
-    if [ "${string#*$substring}" != "$string" ]
-    then
-        return 0    # $substring is in $string
-    else
-        return 1    # $substring is not in $string
-    fi
-}
-
 # Extracts commandline args from the newest running processes named like the first parameter
 get_command_line_args() {
     PROC="$1"
diff --git a/tests/2_docker_daemon_configuration.sh b/tests/2_docker_daemon_configuration.sh
index 641e3a0..d9cd31b 100644
--- a/tests/2_docker_daemon_configuration.sh
+++ b/tests/2_docker_daemon_configuration.sh
@@ -5,8 +5,7 @@ info "2 - Docker Daemon Configuration"
 
 # 2.1
 check_2_1="2.1  - Restrict network traffic between containers"
-get_docker_effective_command_line_args '--icc' | grep "false" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--icc' | grep "false" >/dev/null 2>&1; then
   pass "$check_2_1"
 else
   warn "$check_2_1"
@@ -14,10 +13,8 @@ fi
 
 # 2.2
 check_2_2="2.2  - Set the logging level"
-get_docker_effective_command_line_args '-l' >/dev/null 2>&1
-if [ $? -eq 0 ]; then
-  get_docker_effective_command_line_args '-l' | grep "info" >/dev/null 2>&1
-  if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '-l' >/dev/null 2>&1; then
+  if get_docker_effective_command_line_args '-l' | grep "info" >/dev/null 2>&1; then
     pass "$check_2_2"
   else
     warn "$check_2_2"
@@ -28,8 +25,7 @@ fi
 
 # 2.3
 check_2_3="2.3  - Allow Docker to make changes to iptables"
-get_docker_effective_command_line_args '--iptables' | grep "false" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--iptables' | grep "false" >/dev/null 2>&1; then
   warn "$check_2_3"
 else
   pass "$check_2_3"
@@ -37,8 +33,7 @@ fi
 
 # 2.4
 check_2_4="2.4  - Do not use insecure registries"
-get_docker_effective_command_line_args '--insecure-registry' | grep "insecure-registry" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--insecure-registry' | grep "insecure-registry" >/dev/null 2>&1; then
   warn "$check_2_4"
 else
   pass "$check_2_4"
@@ -46,8 +41,7 @@ fi
 
 # 2.5
 check_2_5="2.5  - Do not use the aufs storage driver"
-docker info 2>/dev/null | grep -e "^Storage Driver:\s*aufs\s*$" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if docker info 2>/dev/null | grep -e "^Storage Driver:\s*aufs\s*$" >/dev/null 2>&1; then
   warn "$check_2_5"
 else
   pass "$check_2_5"
@@ -55,12 +49,9 @@ fi
 
 # 2.6
 check_2_6="2.6  - Configure TLS authentication for Docker daemon"
-get_docker_cumulative_command_line_args '-H' | grep -vE '(unix|fd)://' >/dev/null 2>&1
-if [ $? -eq 0 ]; then
-  get_docker_cumulative_command_line_args '--tlskey' | grep 'tlskey=' >/dev/null 2>&1
-  if [ $? -eq 0 ]; then
-    get_docker_cumulative_command_line_args '--tlsverify' | grep 'tlsverify' >/dev/null 2>&1
-    if [ $? -eq 0 ]; then
+if get_docker_cumulative_command_line_args '-H' | grep -vE '(unix|fd)://' >/dev/null 2>&1; then
+  if get_docker_cumulative_command_line_args '--tlskey' | grep 'tlskey=' >/dev/null 2>&1; then
+    if get_docker_cumulative_command_line_args '--tlsverify' | grep 'tlsverify' >/dev/null 2>&1; then
       pass "$check_2_6"
     else
       warn "$check_2_6"
@@ -78,8 +69,7 @@ fi
 
 # 2.7
 check_2_7="2.7  - Set default ulimit as appropriate"
-get_docker_effective_command_line_args '--default-ulimit' | grep "default-ulimit" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--default-ulimit' | grep "default-ulimit" >/dev/null 2>&1; then
   pass "$check_2_7"
 else
   info "$check_2_7"
@@ -88,8 +78,7 @@ fi
 
 # 2.8
 check_2_8="2.8  - Enable user namespace support"
-get_docker_effective_command_line_args '--userns-remap' | grep "userns-remap" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--userns-remap' | grep "userns-remap" >/dev/null 2>&1; then
   pass "$check_2_8"
 else
   warn "$check_2_8"
@@ -97,8 +86,7 @@ fi
 
 # 2.9
 check_2_9="2.9  - Confirm default cgroup usage"
-get_docker_effective_command_line_args '--cgroup-parent' | grep "cgroup-parent" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--cgroup-parent' | grep "cgroup-parent" >/dev/null 2>&1; then
   warn "$check_2_9"
   info "     * Confirm cgroup usage"
 else
@@ -107,8 +95,7 @@ fi
 
 # 2.10
 check_2_10="2.10 - Do not change base device size until needed"
-get_docker_effective_command_line_args '--storage-opt' | grep "dm.basesize" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--storage-opt' | grep "dm.basesize" >/dev/null 2>&1; then
   warn "$check_2_10"
 else
   pass "$check_2_10"
@@ -116,8 +103,7 @@ fi
 
 # 2.11
 check_2_11="2.11 - Use authorization plugin"
-get_docker_effective_command_line_args '--authorization-plugin' | grep "authorization-plugin" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--authorization-plugin' | grep "authorization-plugin" >/dev/null 2>&1; then
   pass "$check_2_11"
 else
   warn "$check_2_11"
@@ -125,8 +111,7 @@ fi
 
 # 2.12
 check_2_12="2.12 - Configure centralized and remote logging"
-get_docker_effective_command_line_args '--log-driver' | grep "log-driver" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--log-driver' | grep "log-driver" >/dev/null 2>&1; then
   pass "$check_2_12"
 else
   warn "$check_2_12"
@@ -134,8 +119,7 @@ fi
 
 # 2.13
 check_2_13="2.13 - Disable operations on legacy registry (v1)"
-get_docker_effective_command_line_args '--disable-legacy-registry' | grep "disable-legacy-registry" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--disable-legacy-registry' | grep "disable-legacy-registry" >/dev/null 2>&1; then
   pass "$check_2_13"
 else
   warn "$check_2_13"
@@ -155,8 +139,7 @@ fi
 
 # 2.15
 check_2_15="2.15 - Do not enable swarm mode, if not needed"
-docker info 2>/dev/null | grep -e "Swarm:\s*active\s*" >/dev/null 2>&1
-if [ $? -eq 1 ]; then
+if docker info 2>/dev/null | grep -e "Swarm:\s*active\s*" >/dev/null 2>&1; then
   pass "$check_2_15"
 else
   warn "$check_2_15"
@@ -186,8 +169,7 @@ fi
 
 # 2.18
 check_2_18="2.18 - Disable Userland Proxy"
-get_docker_effective_command_line_args '--userland-proxy=false' 2>/dev/null | grep "userland-proxy=false" >/dev/null 2>&1
-if [ $? -eq 0 ]; then
+if get_docker_effective_command_line_args '--userland-proxy=false' 2>/dev/null | grep "userland-proxy=false" >/dev/null 2>&1; then
   pass "$check_2_18"
 else
   warn "$check_2_18"
diff --git a/tests/4_container_images.sh b/tests/4_container_images.sh
index 620a766..7bbca57 100644
--- a/tests/4_container_images.sh
+++ b/tests/4_container_images.sh
@@ -64,8 +64,7 @@ fi
 check_4_6="4.6  - Add HEALTHCHECK instruction to the container image"
 fail=0
 for img in $images; do
-  docker inspect --format='{{.Config.Healthcheck}}' "$img" 2>/dev/null | grep -e "<nil>" >/dev/null 2>&1
-  if [ $? -eq 0 ]; then
+  if docker inspect --format='{{.Config.Healthcheck}}' "$img" 2>/dev/null | grep -e "<nil>" >/dev/null 2>&1; then
     if [ $fail -eq 0 ]; then
       fail=1
       warn "$check_4_6"
@@ -84,8 +83,7 @@ fi
 check_4_7="4.7  - Do not use update instructions alone in the Dockerfile"
 fail=0
 for img in $images; do
-  docker history "$img" 2>/dev/null | grep -e "update" >/dev/null 2>&1
-  if [ $? -eq 0 ]; then
+  if docker history "$img" 2>/dev/null | grep -e "update" >/dev/null 2>&1; then
     if [ $fail -eq 0 ]; then
       fail=1
       info "$check_4_7"