diff --git a/tests/assemble-quest.test.sh b/tests/assemble-quest.test.sh
index 68def40f..73869f06 100755
--- a/tests/assemble-quest.test.sh
+++ b/tests/assemble-quest.test.sh
@@ -3,7 +3,7 @@
 set -e
 
 EXECUTABLE="$1"
-if [ "$EXECUTABLE" == "" ]; then
+if [ -z "$EXECUTABLE" ]; then
   EXECUTABLE="./newserv"
 fi
 
diff --git a/tests/compression.sh b/tests/compression.sh
index bc3b4997..bf23d480 100755
--- a/tests/compression.sh
+++ b/tests/compression.sh
@@ -5,7 +5,7 @@ set -e
 SCHEME=$1
 
 EXECUTABLE="$2"
-if [ "$EXECUTABLE" == "" ]; then
+if [ -z "$EXECUTABLE" ]; then
   EXECUTABLE="./newserv"
 fi
 
diff --git a/tests/custom-sjis.test.sh b/tests/custom-sjis.test.sh
index 1a471827..87c5cac5 100755
--- a/tests/custom-sjis.test.sh
+++ b/tests/custom-sjis.test.sh
@@ -3,7 +3,7 @@
 set -e
 
 EXECUTABLE="$1"
-if [ "$EXECUTABLE" == "" ]; then
+if [ -z "$EXECUTABLE" ]; then
   EXECUTABLE="./newserv"
 fi
 
diff --git a/tests/decode-gci-quest.test.sh b/tests/decode-gci-quest.test.sh
index 5fe93177..e01aa8dd 100755
--- a/tests/decode-gci-quest.test.sh
+++ b/tests/decode-gci-quest.test.sh
@@ -3,7 +3,7 @@
 set -e
 
 EXECUTABLE="$1"
-if [ "$EXECUTABLE" == "" ]; then
+if [ -z "$EXECUTABLE" ]; then
   EXECUTABLE="./newserv"
 fi
 
diff --git a/tests/decode-vms-quest.test.sh b/tests/decode-vms-quest.test.sh
index c5325fcc..3d0a3ca1 100755
--- a/tests/decode-vms-quest.test.sh
+++ b/tests/decode-vms-quest.test.sh
@@ -3,7 +3,7 @@
 set -e
 
 EXECUTABLE="$1"
-if [ "$EXECUTABLE" == "" ]; then
+if [ -z "$EXECUTABLE" ]; then
   EXECUTABLE="./newserv"
 fi
 
diff --git a/tests/decrypt-gci-save.test.sh b/tests/decrypt-gci-save.test.sh
index 01a22a8d..502017f8 100755
--- a/tests/decrypt-gci-save.test.sh
+++ b/tests/decrypt-gci-save.test.sh
@@ -3,7 +3,7 @@
 set -e
 
 EXECUTABLE="$1"
-if [ "$EXECUTABLE" == "" ]; then
+if [ -z "$EXECUTABLE" ]; then
   EXECUTABLE="./newserv"
 fi
 
diff --git a/tests/decrypt-pc-save.test.sh b/tests/decrypt-pc-save.test.sh
index d8712181..7b66308c 100755
--- a/tests/decrypt-pc-save.test.sh
+++ b/tests/decrypt-pc-save.test.sh
@@ -3,7 +3,7 @@
 set -e
 
 EXECUTABLE="$1"
-if [ "$EXECUTABLE" == "" ]; then
+if [ -z "$EXECUTABLE" ]; then
   EXECUTABLE="./newserv"
 fi
 
diff --git a/tests/load-maps.test.sh b/tests/load-maps.test.sh
index 60a15fef..50b5496d 100755
--- a/tests/load-maps.test.sh
+++ b/tests/load-maps.test.sh
@@ -3,7 +3,7 @@
 set -e
 
 EXECUTABLE="$1"
-if [ "$EXECUTABLE" == "" ]; then
+if [ -z "$EXECUTABLE" ]; then
   EXECUTABLE="./newserv"
 fi