more tests for Proc::Async

in particular:
* test .write and .print, open for writing
* .close-stdin
* more exceptions

S17-procasync/basic.t

@@ -2,7 +2,7 @@ use v6;
 
 use Test;
 
-plan 14;
+plan 24;
 
 my $pc = $*DISTRO.is-win
     ?? Proc::Async.new( 'cmd', </c echo Hello World> )
@@ -24,11 +24,11 @@ isa_ok $pm, Promise;
 
 throws_like { $pc.start }, X::Proc::Async::AlreadyStarted;
 
-throws_like { $pc.print("foo") }, X::Proc::Async::OpenForWriting, :method<print>;
-throws_like { $pc.say("foo") }, X::Proc::Async::OpenForWriting, :method<say>;
+throws_like { $pc.print("foo")      }, X::Proc::Async::OpenForWriting, :method<print>;
+throws_like { $pc.say("foo")        }, X::Proc::Async::OpenForWriting, :method<say>;
 throws_like { $pc.write(Buf.new(0)) }, X::Proc::Async::OpenForWriting, :method<write>;
 
-throws_like { $pc.stdout.tap(&say) }, X::Proc::Async::TapBeforeSpawn, :handle<stdout>;
+throws_like { $pc.stdout.tap(&say)  }, X::Proc::Async::TapBeforeSpawn, :handle<stdout>;
 
 my $ps = await $pm;
 isa_ok $ps, Proc::Status;
@@ -37,3 +37,37 @@ is $ps.?exit, 0, 'is the status ok';
 
 is $stdout, "Hello World\n", 'did we get STDOUT';
 is $stderr, "",              'did we get STDERR';
+
+# now test one for writing
+
+$pc = $*DISTRO.is-win
+    ?? Proc::Async.new( :w, 'cmd', </c type con> )
+    !! Proc::Async.new( :w, 'cat', );
+
+throws_like { $pc.close-stdin }, X::Proc::Async::MustBeStarted, :method<close-stdin>;
+throws_like { $pc.kill },        X::Proc::Async::MustBeStarted, :method<kill>;
+throws_like { $pc.say(42) },     X::Proc::Async::MustBeStarted, :method<say>;
+throws_like { $pc.print(42) },   X::Proc::Async::MustBeStarted, :method<print>;
+throws_like { $pc.write(Buf.new(0)) }, X::Proc::Async::MustBeStarted, :method<write>;
+
+$stdout = '';
+$stderr = '';
+$pc.stdout.act: { $stdout ~= $_.subst("\r", "", :g) };
+$pc.stdout.act: { $stderr ~= $_.subst("\r", "", :g) };
+
+throws_like { $pc.stdout(:bin) }, X::Proc::Async::CharsOrBytes, :handle<stdout>;
+
+my $start-promise := $pc.start;
+
+# "Perl" as hex:
+my $write-promise = $pc.write(Buf.new(0x50, 0x65, 0x72, 0x6c));
+isa_ok $write-promise, Promise, '.write returned a promise';
+await $write-promise;
+my $print-promise = $pc.print(' 6');
+isa_ok $print-promise, Promise, '.print returned a promise';
+
+is $start-promise.status, Planned, 'external program still running (stdin still open)';
+
+$pc.close-stdin;
+
+isa_ok $start-promise.result, Proc::Status, 'Can finish, return Proc::Statu';