meson: enable test suite

devel/meson/Portfile

@@ -50,3 +50,27 @@ post-destroot {
     ln -s  ${python_prefix}/bin/meson ${destroot}${prefix}/bin/meson
     ln -s  ${python_prefix}/share/man/man1/meson.1 ${destroot}${prefix}/share/man/man1
 }
+
+# the following block avoids requiring users to 'sudo port select python3 python37'
+# doing a file test for ${prefix}/bin/python3 and requiring this 
+# to be honest would have been much simpler, but not the "MacPorts way"
+pre-test {
+    reinplace "s|/usr/bin/env python3|/usr/bin/env python3.7|" \
+        ${worksrcpath}/run_tests.py \
+        ${worksrcpath}/run_cross_test.py \
+        ${worksrcpath}/run_meson_command_tests.py \
+        ${worksrcpath}/run_project_tests.py \
+        ${worksrcpath}/run_unittests.py
+
+    set testpath "${worksrcpath}/test\\ cases"
+    fs-traverse f ${testpath} {
+        if { [string match *.py ${f}] } {
+            reinplace "s|/usr/bin/env python3|/usr/bin/env python3.7|" ${f}
+        }
+    }
+}
+
+test.run            yes
+test.env-append     configure.env{*}
+test.cmd            ./run_tests.py
+test.target