Emulate the existing behavior and pretend the test already started.

Doing this mostly for compatibility.

For #242

lib/Test/Builder/Tester.pm

@@ -92,13 +92,18 @@ sub _start_testing {
 
     # Make a detached TestState
     my $state = $original_state->create(
-        formatters      => [$formatter],
+        formatters      => [],
 
         # Preserve existing handlers
         early_handlers  => $original_state->early_handlers,
         late_handlers   => $original_state->late_handlers,
     );
 
+    # To emulate existing behavior, start testing but don't
+    # let the formatter see it
+    $state->post_event( TB2::Event::TestStart->new );
+    $state->add_formatters($formatter);
+
     # remember that we're testing
     $testing     = 1;
 

t/Tester/change_formatter.t

@@ -9,8 +9,7 @@ use Test::More;
 note "change_formatter_class"; {
     change_formatter_class("TB2::Formatter::TAP");
 
-    test_out("TAP version 13");
-    test_out("1..2");
-    plan tests => 2;
+    test_out("ok 1");
+    ok(1, "");
     test_test("using the new formatter");
 }