Use #!/bin/sh instead of #!/bin/bash

/bin/bash is absent in some systems (e.g. Alpine Linux used in Docker), /bin/sh is more portable

test/run_all_tests.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 if [[ $1 == "--help" ]]; then
   echo "Pass custom mpirun command line as arguments to the testing script, e.g.:"