diff --git a/scripts/run-tests.sh b/scripts/run-tests.sh
index 7106bba..974ca4b 100755
--- a/scripts/run-tests.sh
+++ b/scripts/run-tests.sh
@@ -1,18 +1,27 @@
 #!/bin/bash
-set -euo pipefail
-ROOT="$(cd -- "$(dirname -- "$0")" && pwd)"
-cd "$ROOT"
-if ! command -v xcodebuild >/dev/null 2>&1; then
-  echo 'ERROR: Xcode and xcodebuild are required on macOS.' >&2
-  exit 1
+# Compatible with bash and zsh, whether launched directly or via /bin/zsh.
+set -uo pipefail
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+if [ ! -d "$ROOT/DBSyn.xcodeproj" ]; then
+  echo "ERROR: DBSyn.xcodeproj not found at $ROOT" >&2
+  exit 2
 fi
-mkdir -p test-results
-STAMP="$(date +%Y%m%d-%H%M%S)"
+if ! command -v xcodebuild >/dev/null 2>&1; then
+  echo 'ERROR: xcodebuild requires Xcode on macOS.' >&2
+  exit 2
+fi
+cd "$ROOT" || exit 2
+mkdir -p "$ROOT/test-results"
+STAMP="$(date +%Y%m%d-%H%M%S)-$$"
 RESULT="$ROOT/test-results/DBSyn-$STAMP.xcresult"
 LOG="$ROOT/test-results/DBSyn-$STAMP.log"
 echo "Running DBSyn XCTest suite. Log: $LOG"
-if xcodebuild test \
-  -project DBSyn.xcodeproj \
+# pipefail preserves xcodebuild's failure even though output is piped to tee.
+# Avoid PIPESTATUS, which is Bash-specific and fails under zsh with nounset.
+set +e
+xcodebuild test \
+  -project "$ROOT/DBSyn.xcodeproj" \
   -scheme DBSyn \
   -configuration Debug \
   -destination 'platform=macOS,arch=arm64' \
@@ -21,10 +30,7 @@ if xcodebuild test \
   ONLY_ACTIVE_ARCH=YES \
   ENABLE_TESTABILITY=YES \
   SWIFT_ENABLE_EXPLICIT_MODULES=NO \
-  CODE_SIGNING_ALLOWED=NO 2>&1 | tee "$LOG"; then
-  STATUS=0
-else
-  STATUS=${PIPESTATUS[0]}
-fi
+  CODE_SIGNING_ALLOWED=NO 2>&1 | tee "$LOG"
+STATUS=$?
 printf '\nTest log: %s\nTest results: %s\n' "$LOG" "$RESULT"
 exit "$STATUS"