diff --git a/tests/unit/init.bats b/tests/unit/init.bats
index 1cd143a32..c432a934c 100644
--- a/tests/unit/init.bats
+++ b/tests/unit/init.bats
@@ -22,9 +22,10 @@ teardown() {
 
   local CIDS=$(get_app_container_ids "$APP")
 
-  run "$DOCKER_BIN" container top "$CIDS"
+  run /bin/bash -c "$DOCKER_BIN container top $CIDS"
   echo "output: $output"
-  assert_output_contains "<defunct>" "0"
+  echo "status: $status"
+  assert_output_not_contains "<defunct>"
 }
 
 @test "(init) dockerfile no tini" {
@@ -37,9 +38,10 @@ teardown() {
 
   local CIDS=$(get_app_container_ids "$APP")
 
-  run "$DOCKER_BIN" container top "$CIDS"
+  run /bin/bash -c "$DOCKER_BIN container top $CIDS"
   echo "output: $output"
-  assert_output_contains "<defunct>" "0"
+  echo "status: $status"
+  assert_output_not_contains "<defunct>"
 }
 
 @test "(init) dockerfile with tini" {
@@ -52,7 +54,8 @@ teardown() {
 
   local CIDS=$(get_app_container_ids "$APP")
 
-  run "$DOCKER_BIN" container top "$CIDS"
+  run /bin/bash -c "$DOCKER_BIN container top $CIDS"
   echo "output: $output"
-  assert_output_contains "<defunct>" "0"
+  echo "status: $status"
+  assert_output_not_contains "<defunct>"
 }
diff --git a/tests/unit/test_helper.bash b/tests/unit/test_helper.bash
index 60ba322e9..a998d67bc 100644
--- a/tests/unit/test_helper.bash
+++ b/tests/unit/test_helper.bash
@@ -143,11 +143,8 @@ assert_output_contains() {
   local input="$output"
   local expected="$1"
   local count="${2:-1}"
-  local found=0
-  until [ "${input/$expected/}" = "$input" ]; do
-    input="${input/$expected/}"
-    found=$((found + 1))
-  done
+  local found
+  found=$(printf '%s' "$input" | { grep -F -o -- "$expected" || true; } | wc -l | tr -d ' ')
 
   if [[ "$count" -eq -1 ]]; then
     if [[ "$found" -gt 0 ]]; then
diff --git a/tests/unit/traefik.bats b/tests/unit/traefik.bats
index f07f2a6f6..0cfc6dc13 100644
--- a/tests/unit/traefik.bats
+++ b/tests/unit/traefik.bats
@@ -468,7 +468,7 @@ teardown() {
   assert_success
   assert_output_contains "dns provider cf_api_email"
   assert_output_contains "dns provider cf_api_key"
-  assert_output_contains "*******"
+  assert_output_contains "*******" 2
   assert_output_not_contains "test@example.com"
   assert_output_not_contains "secret-key"
 
@@ -548,7 +548,7 @@ teardown() {
   echo "output: $output"
   echo "status: $status"
   assert_success
-  assert_output_contains "*******"
+  assert_output_contains "*******" 2
   assert_output_not_contains "test@example.com"
   assert_output_not_contains "secret-key"