Test IO::Handle.seek

Fixes #219

It currently throws when seeking past start of file, but doesn't complain
about seeking past end. I left throwage tests commented out for now,
will make figuring out the failure modes as part of IO improvement stuff.

Author: zoffixznet

S32-io/seek.t

@@ -0,0 +1,84 @@
+use v6;
+use Test;
+
+plan 3;
+
+constant PATH = 't-S32-io-seek-t.tmp';
+LEAVE unlink PATH;
+
+sink my $fh = open PATH, :rw, :bin, :enc<ASCII>;
+$fh.print: '1234567890abcdefghijABCDEFGHIJ';
+
+subtest 'SeekFromBeginning' => {
+    LEAVE $fh.seek: 0, SeekFromBeginning; $fh.seek: 0, SeekFromBeginning;
+
+    $fh.seek: 0, SeekFromBeginning;
+    is-deeply $fh.read(5).decode, '12345', 'seek 0';
+    $fh.seek: 3, SeekFromBeginning;
+    is-deeply $fh.read(5).decode, '45678', 'seek 3';
+
+    $fh.seek: 10, SeekFromBeginning;
+    $fh.seek: 20, SeekFromBeginning;
+    is-deeply $fh.read(5).decode, 'ABCDE', 'two successive seeks';
+
+    # TODO XXX Currently throws just past beginning; Should it fail on both?
+    # throws-like { $fh.seek: -300, SeekFromBeginning }, Exception,
+    #     'seeking past beginning throws';
+    #
+    # throws-like { $fh.seek:  300, SeekFromBeginning }, Exception,
+    #     'seeking past end throws';
+}
+
+subtest 'SeekFromCurrent' => {
+    LEAVE $fh.seek: 0, SeekFromBeginning; $fh.seek: 0, SeekFromBeginning;
+
+    $fh.seek:  10, SeekFromCurrent;
+    is-deeply $fh.read(5).decode, 'abcde', 'seek 10';
+    $fh.seek:  5, SeekFromCurrent;
+    is-deeply $fh.read(5).decode, 'ABCDE', 'read 5, then seek 5';
+    $fh.seek: -20, SeekFromCurrent;
+    is-deeply $fh.read(5).decode, '67890', 'negative seek 20';
+
+    $fh.seek:   5, SeekFromCurrent;
+    $fh.seek:  10, SeekFromCurrent;
+    is-deeply $fh.read(5).decode, 'FGHIJ', 'two successive seeks (pos, pos)';
+
+    $fh.seek: -15, SeekFromCurrent;
+    $fh.seek:   5, SeekFromCurrent;
+    is-deeply $fh.read(5).decode, 'ABCDE', 'two successive seeks (neg, pos)';
+
+    $fh.seek:  -5, SeekFromCurrent;
+    $fh.seek: -10, SeekFromCurrent;
+    is-deeply $fh.read(5).decode, 'abcde', 'two successive seeks (neg, neg)';
+
+    # TODO XXX Currently throws just past beginning; Should it fail on both?
+    # throws-like { $fh.seek: -300, SeekFromCurrent }, Exception,
+    #     'seeking past beginning throws';
+
+    # throws-like {
+    #     $fh.seek:    0, SeekFromBeginning;
+    #     $fh.seek:  300, SeekFromCurrent;
+    # }, Exception, 'seeking past end throws';
+}
+
+subtest 'SeekFromEnd' => {
+    LEAVE $fh.seek: 0, SeekFromBeginning; $fh.seek: 0, SeekFromBeginning;
+
+    $fh.seek:  -5, SeekFromEnd;
+    is-deeply $fh.read(5).decode, 'FGHIJ', 'seek -5';
+    $fh.seek: -30, SeekFromEnd;
+    is-deeply $fh.read(5).decode, '12345', 'seek -30';
+
+    $fh.seek: -5, SeekFromEnd;
+    $fh.seek: -10, SeekFromEnd;
+    is-deeply $fh.read(5).decode, 'ABCDE', 'two successive seeks';
+
+    # TODO XXX Currently throws just past beginning; Should it fail on both?
+    # throws-like { $fh.seek: -300, SeekFromEnd }, Exception,
+    #     'seeking past beginning throws';
+
+    # throws-like { $fh.seek:  300, SeekFromEnd }, Exception,
+    #     'seeking past end throws';
+}
+
+# vim: ft=perl6