diff --git a/sh/tests/calculator_test.sh b/sh/tests/calculator_test.sh
index ea946ca78..7fed8919c 100755
--- a/sh/tests/calculator_test.sh
+++ b/sh/tests/calculator_test.sh
@@ -1,33 +1,22 @@
 #!/usr/bin/env bash
 
-# set -euo pipefail
-IFS='
-'
+set -euo pipefail
 
-script_dirS=$(cd -P "$(dirname "$BASH_SOURCE")" &>/dev/null && pwd)
+script_dir=$(cd -P "$(dirname "$BASH_SOURCE")" && pwd)
 
 challenge() {
-    submitted="./calculator.sh $@
-    "
-    expected="./calculator.sh $@
-    "
-    submitted+=$(2>&1 bash "$script_dirS"/student/calculator.sh "$@")
-    submitted+="
-    exit status: $?"
-    expected+=$(2>&1 bash "$script_dirS"/solutions/calculator.sh "$@")
-    expected+="
-    exit status: $?"
-
-    diff -U 1 <(echo "$submitted") <(echo "$expected")
-    if [ $? != 0 ]
-    then
+    local submitted expected
+    submitted=$(./calculator.sh "$@" 2>&1)
+    expected=$(bash "$script_dir/student/calculator.sh" "$@" 2>&1)
+
+    if ! diff -U 1 <(echo "$submitted") <(echo "$expected") &>/dev/null; then
+        echo "Test failed for input: $@"
         exit 1
     fi
 }
 
 # Check if student uses case statement
-if [[ $(cat "$script_dirS"/student/calculator.sh | grep case | wc -l) -eq 0 ]]
-    then
+if ! grep -q 'case' "$script_dir/student/calculator.sh"; then
     echo "Error: the use of case statement is mandatory"
     exit 1
 fi
@@ -49,7 +38,6 @@ challenge "-3491" "/" "-67"
 challenge "-3491" "*" "-67"
 
 # Invalid inputs
-
 challenge
 challenge "-3491" "*" "-67" "10" "12"
 
@@ -58,29 +46,39 @@ challenge "20" "@" "10"
 challenge "10" "*" "67invalid"
 
 # Test operators functions
+source "$script_dir/student/calculator.sh" >/dev/null
 
-source $script_dirS"/student/calculator.sh" 10 + 10 >/dev/null 2>&1
+do_add_test() {
+    if [ $(do_add 11 14) != 25 ]; then
+        echo "error in function do_add"
+        exit 1
+    fi
+}
 
-if [ $(do_add 11 14) != 25 ]
-then
-    echo "error in function do_add"
-    exit 1
-fi
+do_sub_test() {
+    if [ $(do_sub 11 14) != -3 ]; then
+        echo "error in function do_sub"
+        exit 1
+    fi
+}
 
-if [ $(do_sub 11 14) != -3 ]
-then
-    echo "error in function do_sub"
-    exit 1
-fi
+do_mult_test() {
+    if [ $(do_mult 3 5) != 15 ]; then
+        echo "error in function do_mult"
+        exit 1
+    fi
+}
 
-if [ $(do_mult 3 5) != 15 ]
-then
-    echo "error in function do_mult"
-    exit 1
-fi
+do_divide_test() {
+    if [ $(do_divide 50 5) != 10 ]; then
+        echo "error in function do_divide"
+        exit 1
+    fi
+}
 
-if [ $(do_divide 50 5) != 10 ]
-then
-    echo "error in function do_divide"
-    exit 1
-fi
+do_add_test
+do_sub_test
+do_mult_test
+do_divide_test
+
+echo "All tests passed successfully."