Question on TESTS_ENVIRONMENT use in serial-test

[Arthur Schwarz]

In 15.2.2 Older (and discouraged) serial test harness there is an example
of:

   TESTS_ENVIRONMENT = $(PERL) -Mstrict -w
   TESTS = foo.pl bar.pl baz.pl

I haven't written a little Makefile.am to test some conjectures (a pedantic
'guess). The example seems to indicate that the (undefined) $(PERL) compiles
all the programs in TESTS and these programs can only be perl programs. But
since perl requires a shebang (#!/usr/bin/perl) as the first executable
line, the execution might as well be from calling the program from bash. How
do I determine that program execution is from using the TESTS_ENVIRONMENT
variable and not from a direct call to bash?

The appearance is that when TESTS_ENVIRONMENT is used then the only tests
allowed in TESTS are perl programs. Since shell script and perl programs
both have the first line as the shebang, how can I verify that when TESTS
contains a mixed bag of test programs that the TESTS_ENVIRONMENT perl
compiler is called? Or is the assumption that the example requires that when
TESTS_ENVIRONMENT is used that the TESTS variable only reference test
programs which can be compiled by the TESTS_ENVIRONMENT compiler incorrect?

I have tried both with TESTS = perl_program and TESTS = perl_program
bash_script with the same result. 

The basic question is how is the association between the compiler in
TESTS_ENVIRONMENT and the test program in TESTS made. In parallel processing
this association is made explicit using TEST_EXTENSIONS and the various
ext_SOMETHING. There is no clear rule here other than an example which
leaves as many questions as it answers.

Art

=================== Makefile.am ===================

## Process this file with automake to produce Makefile.in

# select testing format
AUTOMAKE_OPTIONS = serial-tests 

# set compiler for perl program
TESTS_ENVIRONMENT = /usr/bin/perl 

# Testing 
check_SCRIPTS      = test1.sh hello.pl
TESTS              = $(check_SCRIPTS)

test1.sh:
        echo '#!/bin/bash'       > test1.sh
        echo "echo 'PASS: 0'"   >> test1.sh
        echo "exit 0"           >> test1.sh
        chmod +x test1.sh
        
hello.pl:
        echo "#!/usr/bin/perl"           > hello.pl
        echo "use warnings; "           >> hello.pl
        echo 'print "Hello, World!\n";' >> hello.pl
        echo "exit 0;"                  >> hello.pl
        chmod +x hello.pl


CLEANFILES         = $(test_SOURCES)