Document {RAKU,PERL6}_TEST_TIMES

Author: stoned

doc/Language/testing.pod6

@@ -111,6 +111,28 @@ B<Note:> Before Rakudo version 2020.05 the environment variable
 C<PERL6_TEST_DIE_ON_FAIL> was used to enable this feature, it is still
 supported but deprecated.
 
+Test timing in microseconds can be emitted by setting the
+C<RAKU_TEST_TIMES> environmental variable:
+
+=for code :lang<shell>
+$ env RAKU_TEST_TIMES=1 raku -e 'use Test; plan 1; pass sleep(1);'
+1..1
+# between two timestamps 0 microseconds
+ok 1 -
+# t=1000721
+
+The same variable can be used within the test file. Set it before loading
+the C<Test> module:
+
+=for code
+BEGIN %*ENV<RAKU_TEST_TIMES> = 1;
+use Test;
+...
+
+B<Note:> Before Rakudo version 2020.05 the environment variable
+C<PERL6_TEST_TIMES> was used to enable this feature, it is still
+supported but deprecated.
+
 =head1 Test plans
 
 Tests plans use L<C<plan>|/type/Test#plan> for declaring how many plans are