assertions: Replace echo with printf

Author: mbland

lib/bats/assertions

@@ -279,7 +279,7 @@ assert_output_matches() {
   local pattern="$1"
 
   if [[ "$#" -ne 1 ]]; then
-    echo "ERROR: ${FUNCNAME[0]} takes exactly one argument" >&2
+    printf 'ERROR: %s takes exactly one argument\n' "${FUNCNAME[0]}" >&2
     return_from_bats_assertion '1'
   else
     assert_matches "$pattern" "$output" 'output'
@@ -568,20 +568,21 @@ __assert_lines() {
 
   if [[ "$lines_diff" -gt '0' ]]; then
     if [[ "$lines_diff" -eq '1' ]]; then
-      echo "There is one more line of output than expected:" >&2
+      printf 'There is one more line of output than expected:\n' >&2
     else
-      echo "There are $lines_diff more lines of output than expected:" >&2
+      printf 'There are %d more lines of output than expected:\n' \
+        "$lines_diff" >&2
     fi
-    local IFS=$'\n'
-    echo "${lines[*]:$num_lines}" >&2
+    printf '%s\n' "${lines[@]:$num_lines}" >&2
     ((++num_errors))
 
   elif [[ "$lines_diff" -lt '0' ]]; then
     lines_diff="$((-lines_diff))"
     if [[ "$lines_diff" -eq '1' ]]; then
-      echo "There is one fewer line of output than expected." >&2
+      printf 'There is one fewer line of output than expected.\n' >&2
     else
-      echo "There are $lines_diff fewer lines of output than expected." >&2
+      printf 'There are %d fewer lines of output than expected.\n' \
+        "$lines_diff" >&2
     fi
     ((++num_errors))
   fi
@@ -610,7 +611,7 @@ __assert_file() {
 
   if [[ "$assertion" == 'assert_matches' ]]; then
     if [[ "$#" -ne '1' ]]; then
-      echo "ERROR: ${FUNCNAME[1]} takes exactly two arguments" >&2
+      printf 'ERROR: %s takes exactly two arguments\n' "${FUNCNAME[1]}" >&2
       return '1'
     fi
     constraints=("$1" "$output" "The content of '$file_path'")