Fix test: Don't run binaries with -h flag

MFC binaries don't support -h for help. Instead, they expect input files
and will error if those files don't exist. Update tests to only verify
that binaries exist and are executable, without trying to run them.

Changes:
- Replace system() calls with assert_predicate checks
- Update CI workflow to use which and test -x instead of running with -h
- This avoids MPI_ABORT errors when binaries look for missing input files

Author: sbryngelson

.github/workflows/homebrew.yml

@@ -58,12 +58,16 @@ jobs:
           echo "Running Homebrew formula tests..."
           brew test mfc
       
-      - name: Test MFC commands
+      - name: Test MFC binaries
         run: |
-          echo "Testing binaries..."
-          pre_process -h
-          simulation -h
-          post_process -h
+          echo "Verifying binaries are in PATH and executable..."
+          which pre_process
+          which simulation
+          which post_process
+          test -x $(which pre_process)
+          test -x $(which simulation)
+          test -x $(which post_process)
+          echo "All binaries are accessible and executable!"
       
       - name: Verify installation structure
         run: |

packaging/homebrew/mfc.rb

@@ -58,17 +58,16 @@ def caveats
   end
 
   test do
-    # Test that the binaries exist and can execute
-    assert_path_exists bin/"pre_process"
-    assert_path_exists bin/"simulation"
-    assert_path_exists bin/"post_process"
-
-    # Test that binaries show help (basic functionality check)
-    system bin/"pre_process", "-h"
-    system bin/"simulation", "-h"
+    # Test that the binaries exist and are executable
+    assert_predicate bin/"pre_process", :exist?
+    assert_predicate bin/"pre_process", :executable?
+    assert_predicate bin/"simulation", :exist?
+    assert_predicate bin/"simulation", :executable?
+    assert_predicate bin/"post_process", :exist?
+    assert_predicate bin/"post_process", :executable?
 
     # Verify examples were installed
-    assert_path_exists pkgshare/"examples"
-    assert_path_exists pkgshare/"examples/1D_sodshocktube/case.py"
+    assert_predicate pkgshare/"examples", :exist?
+    assert_predicate pkgshare/"examples/1D_sodshocktube/case.py", :exist?
   end
 end