fix(test-doubles): use builtin echo/printf in spy to prevent recursion (#607) (#614)

Co-authored-by: SauronBot <sauronbot@users.noreply.github.com>

Author: SauronBot

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+### Fixed
+- Fix spying on `echo` or `printf` causing bashunit to hang due to infinite recursion (#607)
+
 ## [0.34.1](https://github.com/TypedDevs/bashunit/compare/0.34.0...0.34.1) - 2026-03-20
 
 ### Added

src/helpers.sh

@@ -273,11 +273,11 @@ function bashunit::helper::normalize_variable_name() {
   normalized_string="${input_string//[^a-zA-Z0-9_]/_}"
 
   local _re='^[a-zA-Z_]'
-  if [ "$(echo "$normalized_string" | "$GREP" -cE "$_re" || true)" -eq 0 ]; then
+  if [ "$(builtin echo "$normalized_string" | "$GREP" -cE "$_re" || true)" -eq 0 ]; then
     normalized_string="_$normalized_string"
   fi
 
-  echo "$normalized_string"
+  builtin echo "$normalized_string"
 }
 
 function bashunit::helper::get_provider_data() {

src/test_doubles.sh

@@ -34,7 +34,7 @@ function bashunit::mock() {
   if [ $# -gt 0 ]; then
     eval "function $command() { $* \"\$@\"; }"
   else
-    eval "function $command() { echo \"$($CAT)\" ; }"
+    eval "function $command() { builtin echo \"$($CAT)\" ; }"
   fi
 
   export -f "${command?}"
@@ -61,14 +61,14 @@ function bashunit::spy() {
     local serialized=\"\"
     local arg
     for arg in \"\$@\"; do
-      serialized=\"\$serialized\$(printf '%q' \"\$arg\")$'\\x1f'\"
+      serialized=\"\$serialized\$(builtin printf '%q' \"\$arg\")$'\\x1f'\"
     done
     serialized=\${serialized%$'\\x1f'}
-    printf '%s\x1e%s\\n' \"\$raw\" \"\$serialized\" >> '$params_file'
+    builtin printf '%s\x1e%s\\n' \"\$raw\" \"\$serialized\" >> '$params_file'
     local _c
-    _c=\$(cat '$times_file' 2>/dev/null || echo 0)
+    _c=\$(cat '$times_file' 2>/dev/null || builtin echo 0)
     _c=\$((_c+1))
-    echo \"\$_c\" > '$times_file'
+    builtin echo \"\$_c\" > '$times_file'
   }"
 
   export -f "${command?}"
@@ -83,7 +83,7 @@ function assert_have_been_called() {
   local file_var="${variable}_times_file"
   local times=0
   if [ -f "${!file_var-}" ]; then
-    times=$(cat "${!file_var}" 2>/dev/null || echo 0)
+    times=$(cat "${!file_var}" 2>/dev/null || builtin echo 0)
   fi
   local label="${2:-$(bashunit::helper::normalize_test_function_name "${FUNCNAME[1]}")}"
 
@@ -141,7 +141,7 @@ function assert_have_been_called_times() {
   local file_var="${variable}_times_file"
   local times=0
   if [ -f "${!file_var-}" ]; then
-    times=$(cat "${!file_var}" 2>/dev/null || echo 0)
+    times=$(cat "${!file_var}" 2>/dev/null || builtin echo 0)
   fi
   local label="${3:-$(bashunit::helper::normalize_test_function_name "${FUNCNAME[1]}")}"
   if [ "$times" -ne "$expected_count" ]; then
@@ -170,7 +170,7 @@ function assert_have_been_called_nth_with() {
 
   local times=0
   if [ -f "${!times_file_var-}" ]; then
-    times=$(cat "${!times_file_var}" 2>/dev/null || echo 0)
+    times=$(cat "${!times_file_var}" 2>/dev/null || builtin echo 0)
   fi
 
   if [ "$nth" -gt "$times" ]; then

tests/functional/doubles_test.sh

@@ -106,3 +106,21 @@ function test_mock_mktemp_does_not_break_spy_creation() {
   assert_have_been_called_times 1 rm
   assert_have_been_called_with rm "-f" "/tmp/mocked_temp_file"
 }
+
+function test_spy_on_echo_does_not_hang() {
+  source ./tests/functional/fixtures/echo_function.sh
+  bashunit::spy echo
+
+  write_message "hello world"
+
+  assert_have_been_called echo
+}
+
+function test_spy_on_printf_does_not_hang() {
+  source ./tests/functional/fixtures/printf_function.sh
+  bashunit::spy printf
+
+  format_message "hello world"
+
+  assert_have_been_called printf
+}

tests/functional/fixtures/echo_function.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+
+function write_message() {
+  echo "message: $*"
+}

tests/functional/fixtures/printf_function.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+
+function format_message() {
+  printf "formatted: %s\n" "$*"
+}

tests/unit/test_doubles_test.sh

@@ -214,3 +214,5 @@ function test_unsuccessful_spy_nth_called_with_invalid_index() {
       "expected call" "at index 5 but" "only called 1 times")" \
     "$(assert_have_been_called_nth_with 5 ps "first")"
 }
+
+