Update unit test GitHub workflow (#954)

* Update unit test GitHub workflow
* Bump the OS version to 18.5

.github/workflows/unit_tests.yml

@@ -28,7 +28,7 @@ jobs:
 
     steps:
       - name: Select Xcode version
-        run: sudo xcode-select -s /Applications/Xcode_16.3.app/Contents/Developer
+        run: sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
 
       - name: Checkout code
         uses: actions/checkout@v4
@@ -55,13 +55,16 @@ jobs:
           echo "📂 Contents of .build:"
           ls -lah .build || echo ".build directory not found"
 
+      - name: List available simulators
+        run: xcrun simctl list devices available
+
       - name: Build for testing
         run: |
           set -o pipefail && \
           time xcodebuild build-for-testing \
             -workspace Trio.xcworkspace \
             -scheme "Trio Tests" \
-            -destination 'platform=iOS Simulator,name=iPhone 16,OS=18.4' \
+            -destination 'platform=iOS Simulator,name=iPhone 16,OS=18.5' \
 
       - name: Check for uncommitted changes
         run: |
@@ -104,7 +107,7 @@ jobs:
           time xcodebuild test-without-building \
             -workspace Trio.xcworkspace \
             -scheme "Trio Tests" \
-            -destination 'platform=iOS Simulator,name=iPhone 16,OS=18.4' \
+            -destination 'platform=iOS Simulator,name=iPhone 16,OS=18.5' \
             $([ "$ENABLE_PARALLEL_TESTING" = "true" ] && echo "-parallel-testing-enabled YES") \
             2>&1 | tee xcodebuild.log