fortran: new test API (#45470)

* fortran: new test API
* fortran: add provides to gcc package
* fortran: simplify stand-alone test processing

---------

Co-authored-by: Tamara Dahlgren <dahlgren1@llnl.gov>

etc/spack/defaults/packages.yaml

@@ -26,6 +26,7 @@ packages:
       elf: [elfutils]
       fftw-api: [fftw, amdfftw]
       flame: [libflame, amdlibflame]
+      fortran: [gcc]
       fortran-rt: [gcc-runtime, intel-oneapi-runtime]
       fuse: [libfuse]
       gl: [glx, osmesa]

var/spack/repos/builtin/packages/fortran/package.py

@@ -14,18 +14,16 @@ class Fortran(Package):
     homepage = "https://wg5-fortran.org/"
     virtual = True
 
-    def test(self):
+    def test_fortran(self):
+        """Compile and run 'Hello world'"""
+        expected = ["Hello world", "YES!"]
+        fc = which(os.environ["FC"])
+
         test_source = self.test_suite.current_test_data_dir
-
         for test in os.listdir(test_source):
-            filepath = os.path.join(test_source, test)
-            exe_name = "%s.exe" % test
-
-            fc_exe = os.environ["FC"]
-            fc_opts = ["-o", exe_name, filepath]
-
-            compiled = self.run_test(fc_exe, options=fc_opts, installed=True)
-
-            if compiled:
-                expected = ["Hello world", "YES!"]
-                self.run_test(exe_name, expected=expected)
+            exe_name = f"{test}.exe"
+            with test_part(self, f"test_fortran_{test}", f"run {exe_name}"):
+                fc("-o", exe_name, join_path(test_source, test))
+                exe = which(exe_name)
+                out = exe(output=str.split, error=str.split)
+                check_outputs(expected, out)

var/spack/repos/builtin/packages/gcc/package.py

@@ -35,6 +35,7 @@ class Gcc(AutotoolsPackage, GNUMirrorPackage, CompilerPackage):
     license("GPL-2.0-or-later AND LGPL-2.1-or-later")
 
     provides("cxx")
+    provides("fortran")
 
     version("master", branch="master")