diff --git a/tests/Makefile.am b/tests/Makefile.am
index 6bf7eef..86796c3 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -26,7 +26,7 @@ clean-local:
 distclean: distclean-keys
 
 shellcheck:
-	shellcheck -i SC2086 \
+	shellcheck -i SC2086,SC2181 \
 		functions.sh gen-keys.sh install-fsverity.sh \
 		install-mount-idmapped.sh install-openssl3.sh \
 		install-swtpm.sh install-tss.sh softhsm_setup \
diff --git a/tests/boot_aggregate.test b/tests/boot_aggregate.test
index ccc45f9..04aef9b 100755
--- a/tests/boot_aggregate.test
+++ b/tests/boot_aggregate.test
@@ -47,8 +47,7 @@ swtpm_start() {
 	fi
 
 	if [ -n "${swtpm}" ]; then
-		pgrep swtpm
-		if [ $? -eq 0 ]; then
+		if pgrep swtpm; then
 			echo "INFO: Software TPM (swtpm) already running"
 			return 114
 		else
@@ -60,8 +59,7 @@ swtpm_start() {
 	elif [ -n "${tpm_server}" ]; then
 		# tpm_server uses the Microsoft simulator encapsulated packet format
 		export TPM_SERVER_TYPE="mssim"
-		pgrep tpm_server
-		if [ $? -eq 0 ]; then
+		if pgrep tpm_server; then
 			echo "INFO: Software TPM (tpm_server) already running"
 			return 114
 		else
@@ -81,16 +79,13 @@ swtpm_init() {
 	fi
 
 	echo "INFO: Sending software TPM startup"
-	"${TSSDIR}/tssstartup"
-	if [ $? -ne 0 ]; then
+	if ! "${TSSDIR}/tssstartup"; then
 		echo "INFO: Retry sending software TPM startup"
 		sleep 1
-		"${TSSDIR}/tssstartup"
-	fi
-
-	if [ $? -ne 0 ]; then
-		echo "INFO: Software TPM startup failed"
-		return "$SKIP"
+		if ! "${TSSDIR}/tssstartup"; then
+			echo "INFO: Software TPM startup failed"
+			return "$SKIP"
+		fi
 	fi
 
 	echo "INFO: Walking ${BINARY_BIOS_MEASUREMENTS} initializing the software TPM"
@@ -129,8 +124,7 @@ check() {
 	local options=$1
 
 	echo "INFO: Calculating the boot_aggregate (PCRs 0 - 9) for multiple banks"
-	bootaggr=$(evmctl ima_boot_aggregate "${options}")
-	if [ $? -ne 0 ]; then
+	if ! bootaggr=$(evmctl ima_boot_aggregate "${options}"); then
 		echo "${CYAN}SKIP: evmctl ima_boot_aggregate: $bootaggr${NORM}"
 		exit "$SKIP"
 	fi
diff --git a/tests/functions.sh b/tests/functions.sh
index 2105f21..9670b3a 100755
--- a/tests/functions.sh
+++ b/tests/functions.sh
@@ -368,8 +368,7 @@ _softhsm_setup() {
 
   mkdir -p "${SOFTHSM_SETUP_CONFIGDIR}"
 
-  msg=$(./softhsm_setup setup 2>&1)
-  if [ $? -eq 0 ]; then
+  if msg=$(./softhsm_setup setup 2>&1); then
     echo "softhsm_setup setup succeeded: $msg"
     PKCS11_KEYURI=$(echo "$msg" | sed -n 's|^keyuri: \(.*\)|\1|p')
 
diff --git a/tests/ima_hash.test b/tests/ima_hash.test
index e88fd59..9a8d7b6 100755
--- a/tests/ima_hash.test
+++ b/tests/ima_hash.test
@@ -33,8 +33,8 @@ check() {
   # unless it's negative test, then pass to evmctl
   cmd="openssl dgst $OPENSSL_ENGINE -$alg $file"
   echo - "$cmd"
-  hash=$(set -o pipefail; $cmd 2>/dev/null | cut -d' ' -f2)
-  if [ $? -ne 0 ] && _test_expected_to_pass; then
+  if ! hash=$(set -o pipefail; $cmd 2>/dev/null | cut -d' ' -f2) \
+    && _test_expected_to_pass; then
     echo "${CYAN}$alg test is skipped$NORM"
     rm "$file"
     return "$SKIP"
diff --git a/tests/sign_verify.test b/tests/sign_verify.test
index 5cc0393..1b6cf2a 100755
--- a/tests/sign_verify.test
+++ b/tests/sign_verify.test
@@ -185,8 +185,7 @@ check_sign() {
 
   # Insert keyid from cert into PREFIX in-place of marker `:K:'
   if [[ $PREFIX =~ :K: ]]; then
-    keyid=$(_keyid_from_cert "$key")
-    if [ $? -ne 0 ]; then
+    if ! keyid=$(_keyid_from_cert "$key"); then
       color_red
       echo "Unable to determine keyid for $key"
       color_restore
diff --git a/tests/softhsm_setup b/tests/softhsm_setup
index 10e4013..95bf0b1 100755
--- a/tests/softhsm_setup
+++ b/tests/softhsm_setup
@@ -30,8 +30,7 @@ UNAME_S="$(uname -s)"
 
 case "${UNAME_S}" in
 Darwin)
-	msg=$(sudo -v -n)
-	if [ $? -ne 0 ]; then
+	if ! msg=$(sudo -v -n); then
 		echo "Need password-less sudo rights on OS X to change /etc/gnutls/pkcs11.conf"
 		exit 1
 	fi
@@ -113,18 +112,16 @@ slots.removable = false
 _EOF_
 	fi
 
-	msg=$(p11tool --list-tokens 2>&1 | grep "token=${NAME}" | tail -n1)
-	if [ $? -ne 0 ]; then
+	if ! msg=$(p11tool --list-tokens 2>&1 | grep "token=${NAME}" | tail -n1); then
 		echo "Could not list existing tokens"
 		echo "$msg"
 	fi
 	tokenuri=$(echo "$msg" | sed -n 's/.*URL: \([[:print:]*]\)/\1/p')
 
 	if [ -z "$tokenuri" ]; then
-		msg=$(softhsm2-util \
+		if ! msg=$(softhsm2-util \
 			--init-token --pin "${PIN}" --so-pin "${SO_PIN}" \
-			--free --label "${NAME}" 2>&1)
-		if [ $? -ne 0 ]; then
+			--free --label "${NAME}" 2>&1); then
 			echo "Could not initialize token"
 			echo "$msg"
 			return 2
@@ -143,9 +140,8 @@ _EOF_
 			fi
 		fi
 
-		msg=$(p11tool --list-tokens 2>&1 | \
-			grep "token=${NAME}" | tail -n1)
-		if [ $? -ne 0 ]; then
+		if ! msg=$(p11tool --list-tokens 2>&1 | \
+			grep "token=${NAME}" | tail -n1); then
 			echo "Could not list existing tokens"
 			echo "$msg"
 		fi
@@ -156,15 +152,13 @@ _EOF_
 		fi
 
 		# more recent versions of p11tool have --generate-privkey ...
-		msg=$(GNUTLS_PIN=$PIN p11tool \
+		if ! msg=$(GNUTLS_PIN=$PIN p11tool \
 			--generate-privkey=rsa --bits 2048 --label mykey --login \
-			"${tokenuri}" 2>&1)
-		if [ $? -ne 0 ]; then
+			"${tokenuri}" 2>&1); then
 			# ... older versions have --generate-rsa
-			msg=$(GNUTLS_PIN=$PIN p11tool \
+			if ! msg=$(GNUTLS_PIN=$PIN p11tool \
 				--generate-rsa --bits 2048 --label mykey --login \
-				"${tokenuri}" 2>&1)
-			if [ $? -ne 0 ]; then
+				"${tokenuri}" 2>&1); then
 				echo "Could not create RSA key!"
 				echo "$msg"
 				return 5
@@ -184,8 +178,7 @@ _EOF_
 _getkeyuri_softhsm() {
 	local msg tokenuri keyuri
 
-	msg=$(p11tool --list-tokens 2>&1 | grep "token=${NAME}")
-	if [ $? -ne 0 ]; then
+	if ! msg=$(p11tool --list-tokens 2>&1 | grep "token=${NAME}"); then
 		echo "Could not list existing tokens"
 		echo "$msg"
 		return 5
@@ -196,8 +189,7 @@ _getkeyuri_softhsm() {
 		echo "$msg"
 		return 6
 	fi
-	msg=$(p11tool --list-all "${tokenuri}" 2>&1)
-	if [ $? -ne 0 ]; then
+	if ! msg=$(p11tool --list-all "${tokenuri}" 2>&1); then
 		echo "Could not list object under token $tokenuri"
 		echo "$msg"
 		softhsm2-util --show-slots
