Run tests with yath

This will let us run tests in parallel, and creates a more Perl-standard
test development experience.

flake.nix

@@ -126,6 +126,7 @@
                 EmailMIME
                 EmailSender
                 FileSlurp
+                FileWhich
                 IOCompress
                 IPCRun
                 JSON
@@ -145,6 +146,7 @@
                 TermSizeAny
                 TestMore
                 TextDiff
+                Test2Harness
                 TextTable
                 XMLSimple
                 YAML

tests/Makefile.am

@@ -26,7 +26,7 @@ EXTRA_DIST = \
 
 TESTS = \
   set-up.pl \
-  evaluation-tests.pl \
+  test.pl \
   tear-down.pl
 
 check_SCRIPTS = repos

tests/test.pl

@@ -0,0 +1,24 @@
+#!/usr/bin/env perl
+# HARNESS-NO-PRELOAD
+# HARNESS-CAT-LONG
+# THIS IS A GENERATED YATH RUNNER TEST
+use strict;
+use warnings;
+
+use lib 'lib';
+BEGIN {
+    use File::Which qw(which);
+    $App::Yath::Script::SCRIPT = which 'yath';
+}
+use App::Yath::Util qw/find_yath/;
+
+system($^X, find_yath(), '-D', 'test', '--default-search' => './', @ARGV);
+my $exit = $?;
+
+# This makes sure it works with prove.
+print "1..1\n";
+print "not " if $exit;
+print "ok 1 - Passed tests when run by yath\n";
+print STDERR "yath exited with $exit" if $exit;
+
+exit($exit ? 255 : 0);