diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 881f9e3..b5fe6e6 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -22,6 +22,9 @@ jobs:
           go-version: "1.24.6"
 
       - name: Run test script
+        env:
+          MOLE_PERF_BYTES_TO_HUMAN_LIMIT_MS: "6000"
+          MOLE_PERF_GET_FILE_SIZE_LIMIT_MS: "3000"
         run: ./scripts/test.sh
 
   compatibility:
diff --git a/install.sh b/install.sh
index b74820a..6b08dbc 100755
--- a/install.sh
+++ b/install.sh
@@ -61,7 +61,14 @@ ACTION="install"
 
 # Resolve source dir (local checkout, env override, or download).
 needs_sudo() {
-    [[ ! -w "$INSTALL_DIR" ]]
+    if [[ -e "$INSTALL_DIR" ]]; then
+        [[ ! -w "$INSTALL_DIR" ]]
+        return
+    fi
+
+    local parent_dir
+    parent_dir="$(dirname "$INSTALL_DIR")"
+    [[ ! -w "$parent_dir" ]]
 }
 
 maybe_sudo() {
diff --git a/scripts/test.sh b/scripts/test.sh
index 992f20d..627b79e 100755
--- a/scripts/test.sh
+++ b/scripts/test.sh
@@ -10,15 +10,8 @@ PROJECT_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
 
 cd "$PROJECT_ROOT"
 
-RED='\033[0;31m'
-GREEN='\033[0;32m'
-YELLOW='\033[1;33m'
-NC='\033[0m'
-
-readonly ICON_SUCCESS="✓"
-readonly ICON_ERROR="☻"
-readonly ICON_WARNING="●"
-readonly ICON_LIST="•"
+# shellcheck source=lib/core/file_ops.sh
+source "$PROJECT_ROOT/lib/core/file_ops.sh"
 
 echo "==============================="
 echo "Mole Test Runner"
@@ -123,7 +116,7 @@ else
     printf "${RED}${ICON_ERROR} Installation test failed${NC}\n"
     ((FAILED++))
 fi
-rm -rf /tmp/mole-test
+safe_remove "/tmp/mole-test" true || true
 echo ""
 
 echo "==============================="
diff --git a/tests/dev_caches.bats b/tests/dev_caches.bats
index c2d7565..96377d0 100644
--- a/tests/dev_caches.bats
+++ b/tests/dev_caches.bats
@@ -30,6 +30,7 @@ stop_section_spinner() { :; }
 clean_tool_cache() { echo "$1"; }
 safe_clean() { echo "$2"; }
 note_activity() { :; }
+run_with_timeout() { shift; "$@"; }
 pnpm() {
     if [[ "$1" == "store" && "$2" == "prune" ]]; then
         return 0
diff --git a/tests/performance.bats b/tests/performance.bats
index 4ac7a64..dfc4037 100644
--- a/tests/performance.bats
+++ b/tests/performance.bats
@@ -18,6 +18,7 @@ setup() {
 
 @test "bytes_to_human handles large values efficiently" {
     local start end elapsed
+    local limit_ms="${MOLE_PERF_BYTES_TO_HUMAN_LIMIT_MS:-4000}"
 
     bytes_to_human 1073741824 > /dev/null
 
@@ -29,7 +30,7 @@ setup() {
 
     elapsed=$(( (end - start) / 1000000 ))
 
-    [ "$elapsed" -lt 2000 ]
+    [ "$elapsed" -lt "$limit_ms" ]
 }
 
 @test "bytes_to_human produces correct output for GB range" {
@@ -74,6 +75,7 @@ setup() {
     dd if=/dev/zero of="$test_file" bs=1024 count=100 2> /dev/null
 
     local start end elapsed
+    local limit_ms="${MOLE_PERF_GET_FILE_SIZE_LIMIT_MS:-2000}"
     start=$(date +%s%N)
     for i in {1..100}; do
         get_file_size "$test_file" > /dev/null
@@ -82,7 +84,7 @@ setup() {
 
     elapsed=$(( (end - start) / 1000000 ))
 
-    [ "$elapsed" -lt 1000 ]
+    [ "$elapsed" -lt "$limit_ms" ]
 }
 
 @test "get_file_mtime returns valid timestamp" {