Fix grep: invalid option -- P error on Mac

.github/workflows/test-pr.yml

@@ -5,8 +5,13 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
-
+    strategy:
+      matrix:
+        runs-on:
+          - ubuntu-latest
+          - macos-latest
+    name: Test (${{matrix.runs-on}})
+    runs-on: ${{matrix.runs-on}}
     steps:
       - uses: actions/checkout@v4
       - run: ./backport.functions_tests

backport.functions

@@ -5,5 +5,5 @@ set -e
 function get_pr_number() {
 
   local commit_msg=$1
-  echo "$commit_msg" | grep -oP '#(\d+)' | tail -n1 | cut -c2-
+  echo "$commit_msg" | grep --extended-regexp --only-matching '#[0-9]+' | tail -n1 | cut -c2-
 }

backport.functions_tests

@@ -4,9 +4,13 @@ set -eu
 SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
 
 # Source the latest version of assert.sh unit testing library and include in current shell
-assert_script_content=$(curl --silent https://raw.githubusercontent.com/hazelcast/assert.sh/main/assert.sh)
+curl --silent https://raw.githubusercontent.com/hazelcast/assert.sh/main/assert.sh --output assert.sh
+
 # shellcheck source=/dev/null
-. <(echo "${assert_script_content}")
+# You _should_ be able to avoid a temporary file with something like
+# . <(echo "${assert_script_content}")
+# But this doesn't work on the MacOS GitHub runner (but does on MacOS locally)
+. assert.sh
 . "$SCRIPT_DIR"/backport.functions
 
 TESTS_RESULT=0
@@ -15,7 +19,7 @@ function test_get_pr_number {
   local commit_msg=$1
   local expected_pr_number=$2
   local actual_pr_number=$(get_pr_number "$commit_msg")
-  local MSG="Expected PR Number extracted from \"$commit_msg\""
+  local MSG="Expected PR Number extracted from \"$commit_msg\" should be equal to \"$expected_pr_number\""
   assert_eq "$expected_pr_number" "$actual_pr_number" "$MSG" && log_success "$MSG" || TESTS_RESULT=$?
 }