Tests for low-level binary writer

Tests writing varints, fixed32, fixed64, and pairs thereof.

t/binary-writer.t

@@ -0,0 +1,90 @@
+use v6;
+
+use Test;
+use PB::Binary::Writer;
+
+
+# ENCODING TESTS
+
+# Tests for encode-field-key()
+for (0, 1, 2, 3, 200, 60_000, 20_000_000) X ^8 -> $tag, $type {
+    is encode-field-key($tag, $type), $tag +< 3 + $type,
+       "encode-field-key($tag, $type) encodes field key properly";
+}
+
+# Tests for encode-zigzag()
+my @zigzag-pairs = <
+    0     0
+    1    -1
+    2     1
+    3    -2
+    4     2
+    5    -3
+    6     3
+    7    -4
+    8     4
+    4294967294     2147483647
+    4294967295    -2147483648
+>;
+
+for @zigzag-pairs.list -> $coded, $decoded {
+    is encode-zigzag(+$decoded), +$coded, "encode-zigzag($decoded) works";
+}
+
+
+# BUFFER-WRITING TESTS
+
+# Trivial buffer (first example in Google's encoding docs)
+my buf8 $buffer := buf8.new();
+my $offset       = 0;
+write-varint($buffer, $offset, 8);
+is $buffer[0], 0x08, '1-byte varint at offset 0 written correctly';
+is $offset, 1, '... and offset was updated correctly';
+
+write-varint($buffer, $offset, 150);
+is $buffer[1], 0x96, 'First  byte of 2-byte varint at offset 1 written correctly';
+is $buffer[2], 0x01, 'Second byte of 2-byte varint at offset 1 written correctly';
+is $offset, 3, '... and offset was updated correctly';
+
+$buffer := buf8.new();
+$offset  = 0;
+write-pair($buffer, $offset, 1, 0, 150);
+my $trivial := buf8.new(0x08, 0x96, 0x01);
+is_deeply $buffer, $trivial, 'Wrote trivial buffer correctly';
+is $offset, 3, '... and offset was updated correctly';
+
+# Buffer containing fixed size fields
+$buffer := buf8.new();
+$offset  = 1;
+write-fixed32($buffer, $offset, 0x12345678);
+is $buffer[1], 0x78, 'First  byte of fixed32 at offset 1 written correctly';
+is $buffer[2], 0x56, 'Second byte of fixed32 at offset 1 written correctly';
+is $buffer[3], 0x34, 'Third  byte of fixed32 at offset 1 written correctly';
+is $buffer[4], 0x12, 'Fourth byte of fixed32 at offset 1 written correctly';
+is $offset, 5, '... and offset was updated correctly';
+
+$offset = 6;
+write-fixed64($buffer, $offset, 0x12345678BEEFCAFE);
+is $buffer[ 6], 0xFE, 'First   byte of fixed64 at offset 6 written correctly';
+is $buffer[ 7], 0xCA, 'Second  byte of fixed64 at offset 6 written correctly';
+is $buffer[ 8], 0xEF, 'Third   byte of fixed64 at offset 6 written correctly';
+is $buffer[ 9], 0xBE, 'Fourth  byte of fixed64 at offset 6 written correctly';
+is $buffer[10], 0x78, 'Fifth   byte of fixed64 at offset 6 written correctly';
+is $buffer[11], 0x56, 'Sixth   byte of fixed64 at offset 6 written correctly';
+is $buffer[12], 0x34, 'Seventh byte of fixed64 at offset 6 written correctly';
+is $buffer[13], 0x12, 'Eighth  byte of fixed64 at offset 6 written correctly';
+is $offset, 14, '... and offset was updated correctly';
+
+$buffer := buf8.new();
+$offset  = 0;
+write-pair($buffer, $offset, 1, 5, 0x12345678);
+write-pair($buffer, $offset, 2, 1, 0x12345678BEEFCAFE);
+my $fixed-fields := buf8.new(0x0D, 0x78, 0x56, 0x34, 0x12,
+                             0x11, 0xFE, 0xCA, 0xEF, 0xBE,
+                                   0x78, 0x56, 0x34, 0x12);
+is_deeply $buffer, $fixed-fields, 'Wrote fixed fields buffer correctly';
+is $offset, 14, '... and offset was updated correctly';
+
+
+# Tell prove that we've completed testing normally
+done;