diff --git a/CHANGELOG.md b/CHANGELOG.md
index 38662be1..dc949e73 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 - Enable parallel tests on Windows
 - Add `assert_not_called`
 - Improve `find_total_tests` performance
+- Improve `clock` performance
 
 ## [0.19.1](https://github.com/TypedDevs/bashunit/compare/0.19.0...0.19.1) - 2025-05-23
 
diff --git a/src/clock.sh b/src/clock.sh
index 5e851e95..51d4b913 100644
--- a/src/clock.sh
+++ b/src/clock.sh
@@ -1,9 +1,17 @@
 #!/usr/bin/env bash
 
 function clock::now() {
+  if [[ -n ${EPOCHREALTIME+x} && -n "$EPOCHREALTIME" ]]; then
+    local seconds microseconds
+    seconds=${EPOCHREALTIME%%.*}
+    microseconds=${EPOCHREALTIME##*.}
+    printf '%d\n' $((10#$seconds * 1000000000 + 10#$microseconds * 1000))
+    return 0
+  fi
+
   if dependencies::has_perl && perl -MTime::HiRes -e "" > /dev/null 2>&1; then
     if perl -MTime::HiRes -e 'printf("%.0f\n",Time::HiRes::time()*1000000000)'; then
-        return 0
+      return 0
     fi
   fi
 
@@ -52,7 +60,7 @@ function clock::shell_time() {
 function clock::total_runtime_in_milliseconds() {
   end_time=$(clock::now)
   if [[ -n $end_time ]]; then
-    math::calculate "($end_time-$_START_TIME)/1000000"
+    printf '%d\n' $(((end_time - _START_TIME)/1000000))
   else
     echo ""
   fi
@@ -61,7 +69,7 @@ function clock::total_runtime_in_milliseconds() {
 function clock::total_runtime_in_nanoseconds() {
   end_time=$(clock::now)
   if [[ -n $end_time ]]; then
-    math::calculate "($end_time-$_START_TIME)"
+    printf '%d\n' $((end_time - _START_TIME))
   else
     echo ""
   fi
diff --git a/src/env.sh b/src/env.sh
index 50cc5165..c140d854 100644
--- a/src/env.sh
+++ b/src/env.sh
@@ -79,15 +79,19 @@ function env::active_internet_connection() {
 function env::find_terminal_width() {
   local cols=""
 
-  if [[ -z "$cols" ]] && command -v stty > /dev/null; then
+  if command -v tput >/dev/null; then
     cols=$(tput cols 2>/dev/null)
   fi
-  if [[ -n "$TERM" ]] && command -v tput > /dev/null; then
+
+  if [[ -n "$TERM" ]] && command -v stty >/dev/null; then
     cols=$(stty size 2>/dev/null | cut -d' ' -f2)
   fi
 
-  # Directly echo the value with fallback
-  echo "${cols:-100}"
+  if [[ -z "$cols" || "$cols" == "0" ]]; then
+    cols=100
+  fi
+
+  echo "$cols"
 }
 
 function env::print_verbose() {
diff --git a/src/runner.sh b/src/runner.sh
index a39e06ed..a26f266b 100755
--- a/src/runner.sh
+++ b/src/runner.sh
@@ -178,8 +178,8 @@ function runner::run_test() {
   exec 3>&-
 
   local end_time=$(clock::now)
-  local duration_ns=$(math::calculate "($end_time - $start_time) ")
-  local duration=$(math::calculate "$duration_ns / 1000000")
+  local duration_ns=$((end_time - start_time))
+  local duration=$((duration_ns / 1000000))
 
   if env::is_verbose_enabled; then
     if env::is_simple_output_enabled; then
diff --git a/tests/unit/clock_test.sh b/tests/unit/clock_test.sh
index 5ab0d5ba..81edb0ff 100644
--- a/tests/unit/clock_test.sh
+++ b/tests/unit/clock_test.sh
@@ -4,10 +4,12 @@ __ORIGINAL_OS=""
 
 function set_up_before_script() {
   __ORIGINAL_OS=$_OS
+  unset EPOCHREALTIME
 }
 
 function tear_down_after_script() {
   export _OS=$__ORIGINAL_OS
+  unset EPOCHREALTIME
 }
 
 function mock_non_existing_fn() {
@@ -20,6 +22,12 @@ function test_now_with_perl() {
   assert_same "1720705883457" "$(clock::now)"
 }
 
+function test_now_with_epochrealtime() {
+  EPOCHREALTIME="12345.678901"
+
+  assert_same "12345678901000" "$(clock::now)"
+}
+
 function test_now_on_linux_unknown() {
   mock_unknown_linux_os
   mock perl mock_non_existing_fn
diff --git a/tests/unit/directory_test.sh b/tests/unit/directory_test.sh
index eeb26046..4716ed84 100644
--- a/tests/unit/directory_test.sh
+++ b/tests/unit/directory_test.sh
@@ -111,7 +111,7 @@ function test_unsuccessful_assert_is_directory_readable_when_a_file_is_given() {
 }
 
 function test_unsuccessful_assert_is_directory_readable_without_execution_permission() {
-  if [[ "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
+  if [[ "$EUID" -eq 0 || "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
     return
   fi
 
@@ -126,7 +126,7 @@ function test_unsuccessful_assert_is_directory_readable_without_execution_permis
 }
 
 function test_unsuccessful_assert_is_directory_readable_without_read_permission() {
-  if [[ "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
+  if [[ "$EUID" -eq 0 || "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
       return
   fi
 
@@ -141,7 +141,7 @@ function test_unsuccessful_assert_is_directory_readable_without_read_permission(
 }
 
 function test_successful_assert_is_directory_not_readable_without_read_permission() {
-  if [[ "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
+  if [[ "$EUID" -eq 0 || "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
       return
   fi
 
@@ -152,7 +152,7 @@ function test_successful_assert_is_directory_not_readable_without_read_permissio
 }
 
 function test_successful_assert_is_directory_not_readable_without_execution_permission() {
-  if [[ "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
+  if [[ "$EUID" -eq 0 || "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
       return
   fi
 
@@ -178,7 +178,7 @@ function test_successful_assert_is_directory_writable() {
 }
 
 function test_unsuccessful_assert_is_directory_writable() {
-  if [[ "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
+  if [[ "$EUID" -eq 0 || "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
       return
   fi
 
@@ -202,7 +202,7 @@ function test_unsuccessful_assert_is_directory_writable_when_a_file_is_given() {
 }
 
 function test_successful_assert_is_directory_not_writable() {
-  if [[ "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
+  if [[ "$EUID" -eq 0 || "$_OS" == "Windows" || $_DISTRO = "Alpine" ]]; then
       return
   fi