never ending quest for portable bash scripts

cw/tests/test.sh

 #/bin/bash
 uname=`uname`
-if [[ "$uname" -eq "Darwin" ]]; then
+if [ "$uname" = "Darwin" ]; then
   date="gdate"
   readlink="greadlink"
 else
 pass="\033[32mPASSED\033[0m"
 fail="\033[31mFAILED\033[0m"
 
-if [[ "$ret_only" -eq $ret_ans ]]; then
+if [ "$ret_only" -eq $ret_ans ]; then
   echo "return_only ... $pass"
 else
   echo -n "return_only ... $fail"
   echo " expected $ret_ans but got $ret_only"
   overall='1'
 fi
-if [[ "$var_maths" -eq $var_ans ]]; then
+if [ "$var_maths" -eq $var_ans ]; then
   echo "var_maths ..... $pass"
 else
   echo "var_maths ..... $fail"
   echo " expected $var_ans but got $var_maths"
   overall='1'
 fi
-if [[ "$func_call" -eq $func_ans ]]; then
+if [ "$func_call" -eq $func_ans ]; then
   echo "func_call ..... $pass"
 else
   echo -n "func_call ..... $fail"
   echo " expected $func_ans but got $func_call"
   overall='1'
 fi
-if [[ "$cond_loop" -eq $cond_ans ]]; then
+if [ "$cond_loop" -eq $cond_ans ]; then
   echo "cond_loop ..... $pass"
 else
   echo -n "cond_loop ..... $fail"
   echo " expected $cond_ans but got $cond_loop"
   overall='1'
 fi
-if [[ "$func_args" -eq $args_ans ]]; then
+if [ "$func_args" -eq $args_ans ]; then
   echo "func_args ..... $pass"
 else
   echo -n "func_args ..... $fail"