Add TEST_THREADS env var support

Author: coke

xt/space-after-comma.t

@@ -21,19 +21,16 @@ if @*ARGS {
 }
 
 plan +@files;
+my $max-jobs = %*ENV<TEST_THREADS> // 2;
+my %output;
 
-for @files -> $file {
-    my $ok = True;
-
-    my $output = "";
+sub test-promise($promise) {
+    my $file = $promise.command[*-1];
+    test-it(%output{$file}, $file);
+}
 
-    if $file ~~ / '.pod6' $/ {
-        my $a = Proc::Async.new($*EXECUTABLE-NAME, '--doc', $file);
-        $a.stdout.tap(-> $buf { $output = $output ~ $buf });
-        await $a.start;
-    } else {
-        $output = $file.IO.slurp;
-    }
+sub test-it(Str $output, Str $file) {
+    my $ok = True;
 
     for $output.lines -> $line-orig {
         next if $line-orig ~~ / ^ '    '/;
@@ -64,4 +61,24 @@ for @files -> $file {
     ok $ok, "$error: Must have space after comma.";
 }
 
+my @jobs;
+for @files -> $file {
+
+    my $output = "";
+
+    if $file ~~ / '.pod6' $/ {
+        my $a = Proc::Async.new($*EXECUTABLE-NAME, '--doc', $file);
+        %output{$file} = "";
+        $a.stdout.tap(-> $buf { %output{$file} = %output{$file} ~ $buf });
+        push @jobs: $a.start;
+        if +@jobs > $max-jobs {
+            test-promise(await @jobs.shift)
+        }
+    } else {
+        test-it($file.IO.slurp, $file);
+    }
+}
+
+for @jobs.map: {await $_} -> $r { test-promise($r) }
+
 # vim: expandtab shiftwidth=4 ft=perl6