diff --git a/src/summary.sh b/src/summary.sh
index 95f15637..3d8a3c36 100644
--- a/src/summary.sh
+++ b/src/summary.sh
@@ -92,7 +92,7 @@ link_to_results () {
   local push_link="https://github.com/${GITHUB_REPOSITORY}/security/code-scanning?query=tool%3A${SCANNING_TOOL:-"shellcheck"}+branch%3A${GITHUB_REF_NAME:-"main"}+is%3Aopen"
   local pull_request_link="https://github.com/${GITHUB_REPOSITORY}/security/code-scanning?query=pr%3A${pull_number}+tool%3A${SCANNING_TOOL:-"shellcheck"}+is%3Aopen"
 
-  case ${INPUT_TRIGGERING_EVENT:-${GITHUB_EVENT_NAME}} in
+  case ${INPUT_TRIGGERING_EVENT-${GITHUB_EVENT_NAME}} in
     "push")
       echo -e "${push_link}"
       ;;
diff --git a/test/diff_scan_summary.bats b/test/diff_scan_summary.bats
new file mode 100644
index 00000000..9c21b68e
--- /dev/null
+++ b/test/diff_scan_summary.bats
@@ -0,0 +1,87 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+setup_file () {
+  load 'test_helper/common-setup'
+  _common_setup
+}
+
+setup () {
+  load 'test_helper/bats-assert/load'
+  load 'test_helper/bats-support/load'
+}
+
+@test "diff_scan_summary()" {
+  source "${PROJECT_ROOT}/src/summary.sh"
+
+  export only_changed_scripts=("1.sh" "\$2.sh" "3 .sh")
+  INPUT_TRIGGERING_EVENT=""
+
+  echo -e \
+"Error: SHELLCHECK_WARNING:
+src/index.sh:53:10: warning[SC2154]: MAIN_HEADING is referenced but not assigned.
+
+Error: SHELLCHECK_WARNING:
+src/index.sh:56:14: warning[SC2154]: WHITE is referenced but not assigned.
+
+Error: SHELLCHECK_WARNING:
+src/index.sh:56:56: warning[SC2154]: NOCOLOR is referenced but not assigned.
+" > ../defects.log
+
+  echo -e \
+"Error: SHELLCHECK_WARNING:
+src/index.sh:7:3: note[SC1091]: Not following: functions.sh: openBinaryFile: does not exist (No such file or directory)
+" > ../fixes.log
+
+  run diff_scan_summary
+  assert_success
+  assert_output \
+"Changed scripts: \`3\`
+
+|                    | ❌ Added                 | ✅ Fixed                 |
+|:------------------:|:------------------------:|:------------------------:|
+| ⚠️ Errors / Warnings / Notes |  **3**  |  **1**  |"
+}
+
+@test "diff_scan_summary() - no fixes or defects" {
+  source "${PROJECT_ROOT}/src/summary.sh"
+
+  export only_changed_scripts=("1.sh" "\$2.sh" "3 .sh")
+  INPUT_TRIGGERING_EVENT=""
+
+  touch ../defects.log ../fixes.log
+
+  run diff_scan_summary
+  assert_success
+  assert_output \
+"Changed scripts: \`3\`
+
+|                    | ❌ Added                 | ✅ Fixed                 |
+|:------------------:|:------------------------:|:------------------------:|
+| ⚠️ Errors / Warnings / Notes |  **0**  |  **0**  |"
+}
+
+@test "diff_scan_summary() - no changed shell scripts" {
+  source "${PROJECT_ROOT}/src/summary.sh"
+
+  export only_changed_scripts=()
+  INPUT_TRIGGERING_EVENT=""
+
+  touch ../defects.log ../fixes.log
+
+  run diff_scan_summary
+  assert_success
+  assert_output \
+"Changed scripts: \`0\`
+
+|                    | ❌ Added                 | ✅ Fixed                 |
+|:------------------:|:------------------------:|:------------------------:|
+| ⚠️ Errors / Warnings / Notes |  **0**  |  **0**  |"
+}
+
+teardown () {
+  rm -f ../defects.log ../fixes.log
+
+  export \
+    only_changed_scripts="" \
+    INPUT_TRIGGERING_EVENT=""
+}