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string_decoder: Improve test coverage
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The test cases are still essentially the same, but now all possible ways
of writing a buffer into the decoder are tested, which has exposed a few
failing scenarios that had not been discovered so far!
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@felixge @tjfontaine
felixge authored and tjfontaine committed Jun 6, 2014
1 parent 2efe4ab commit 22b8398
Showing 1 changed file with 82 additions and 123 deletions.
205 changes: 82 additions & 123 deletions test/simple/test-string-decoder.js
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Original file line number Diff line number Diff line change
Expand Up @@ -22,142 +22,101 @@
var common = require('../common');
var assert = require('assert');
var StringDecoder = require('string_decoder').StringDecoder;
var decoder = new StringDecoder('utf8');



var buffer = new Buffer('$');
assert.deepEqual('$', decoder.write(buffer));

buffer = new Buffer('¢');
assert.deepEqual('', decoder.write(buffer.slice(0, 1)));
assert.deepEqual('¢', decoder.write(buffer.slice(1, 2)));

buffer = new Buffer('€');
assert.deepEqual('', decoder.write(buffer.slice(0, 1)));
assert.deepEqual('', decoder.write(buffer.slice(1, 2)));
assert.deepEqual('€', decoder.write(buffer.slice(2, 3)));

buffer = new Buffer([0xF0, 0xA4, 0xAD, 0xA2]);
var s = '';
s += decoder.write(buffer.slice(0, 1));
s += decoder.write(buffer.slice(1, 2));
s += decoder.write(buffer.slice(2, 3));
s += decoder.write(buffer.slice(3, 4));
assert.ok(s.length > 0);

// CESU-8
buffer = new Buffer('EDA0BDEDB18D', 'hex'); // THUMBS UP SIGN (in CESU-8)
var s = '';
s += decoder.write(buffer.slice(0, 1));
s += decoder.write(buffer.slice(1, 2));
s += decoder.write(buffer.slice(2, 3)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(3, 4));
s += decoder.write(buffer.slice(4, 5));
s += decoder.write(buffer.slice(5, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 2));
s += decoder.write(buffer.slice(2, 4)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(4, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 3)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(3, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 4)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(4, 5));
s += decoder.write(buffer.slice(5, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 5)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(5, 6)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 6));
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)


// UCS-2
decoder = new StringDecoder('ucs2');
buffer = new Buffer('ab', 'ucs2');
assert.equal(decoder.write(buffer), 'ab'); // 2 complete chars
buffer = new Buffer('abc', 'ucs2');
assert.equal(decoder.write(buffer.slice(0, 3)), 'a'); // 'a' and first of 'b'
assert.equal(decoder.write(buffer.slice(3, 6)), 'bc'); // second of 'b' and 'c'


// UTF-16LE
buffer = new Buffer('3DD84DDC', 'hex'); // THUMBS UP SIGN (in CESU-8)
var s = '';
s += decoder.write(buffer.slice(0, 1));
s += decoder.write(buffer.slice(1, 2)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(2, 3));
s += decoder.write(buffer.slice(3, 4)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 2)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(2, 4)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 3)); // complete lead surrogate
assert.equal(s, '');
s += decoder.write(buffer.slice(3, 4)); // complete trail surrogate
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

var s = '';
s += decoder.write(buffer.slice(0, 4));
assert.equal(s, '\uD83D\uDC4D'); // THUMBS UP SIGN (in UTF-16)

process.stdout.write('scanning ');

// UTF-8
test('utf-8', new Buffer('$', 'utf-8'), '$');
test('utf-8', new Buffer('¢', 'utf-8'), '¢');
test('utf-8', new Buffer('€', 'utf-8'), '€');
test('utf-8', new Buffer('𤭢', 'utf-8'), '𤭢');
// A mixed ascii and non-ascii string
// Test stolen from deps/v8/test/cctest/test-strings.cc
// U+02E4 -> CB A4
// U+0064 -> 64
// U+12E4 -> E1 8B A4
// U+0030 -> 30
// U+3045 -> E3 81 85
var expected = '\u02e4\u0064\u12e4\u0030\u3045';
var buffer = new Buffer([0xCB, 0xA4, 0x64, 0xE1, 0x8B, 0xA4,
0x30, 0xE3, 0x81, 0x85]);
var charLengths = [0, 0, 1, 2, 2, 2, 3, 4, 4, 4, 5, 5];
test(
'utf-8',
new Buffer([0xCB, 0xA4, 0x64, 0xE1, 0x8B, 0xA4, 0x30, 0xE3, 0x81, 0x85]),
'\u02e4\u0064\u12e4\u0030\u3045'
);

// CESU-8
test('utf-8', new Buffer('EDA0BDEDB18D', 'hex'), '\ud83d\udc4d'); // thumbs up

// UCS-2
test('ucs2', new Buffer('ababc', 'ucs2'), 'ababc');

// UTF-16LE
test('ucs2', new Buffer('3DD84DDC', 'hex'), '\ud83d\udc4d'); // thumbs up

// Split the buffer into 3 segments
// |----|------|-------|
// 0 i j buffer.length
// Scan through every possible 3 segment combination
// and make sure that the string is always parsed.
common.print('scanning ');
for (var j = 2; j < buffer.length; j++) {
for (var i = 1; i < j; i++) {
var decoder = new StringDecoder('utf8');
console.log(' crayon!');

var sum = decoder.write(buffer.slice(0, i));
// test verifies that StringDecoder will correctly decode the given input
// buffer with the given encoding to the expected output. It will attempt all
// possible ways to write() the input buffer, see writeSequences(). The
// singleSequence allows for easy debugging of a specific sequence which is
// useful in case of test failures.
function test(encoding, input, expected, singleSequence) {
var sequences;
if (!singleSequence) {
sequences = writeSequences(input.length);
} else {
sequences = [singleSequence];
}
sequences.forEach(function(sequence) {
var decoder = new StringDecoder(encoding);
var output = '';
sequence.forEach(function(write) {
output += decoder.write(input.slice(write[0], write[1]));
});
process.stdout.write('.');
if (output !== expected) {
var message =
'Expected "'+unicodeEscape(expected)+'", '+
'but got "'+unicodeEscape(output)+'"\n'+
'Write sequence: '+JSON.stringify(sequence)+'\n'+
'Decoder charBuffer: 0x'+decoder.charBuffer.toString('hex')+'\n'+
'Full Decoder State: '+JSON.stringify(decoder, null, 2);
assert.fail(output, expected, message);
}
});
}

// just check that we've received the right amount
// after the first write
assert.equal(charLengths[i], sum.length);
// unicodeEscape prints the str contents as unicode escape codes.
function unicodeEscape(str) {
var r = '';
for (var i = 0; i < str.length; i++) {
r += '\\u'+str.charCodeAt(i).toString(16);
}
return r;
}

sum += decoder.write(buffer.slice(i, j));
sum += decoder.write(buffer.slice(j, buffer.length));
assert.equal(expected, sum);
common.print('.');
// writeSequences returns an array of arrays that describes all possible ways a
// buffer of the given length could be split up and passed to sequential write
// calls.
//
// e.G. writeSequences(3) will return: [
// [ [ 0, 3 ] ],
// [ [ 0, 2 ], [ 2, 3 ] ],
// [ [ 0, 1 ], [ 1, 3 ] ],
// [ [ 0, 1 ], [ 1, 2 ], [ 2, 3 ] ]
// ]
function writeSequences(length, start, sequence) {
if (start === undefined) {
start = 0;
sequence = []
} else if (start === length) {
return [sequence];
}
var sequences = [];
for (var end = length; end > start; end--) {
var subSequence = sequence.concat([[start, end]]);
var subSequences = writeSequences(length, end, subSequence, sequences);
sequences = sequences.concat(subSequences);
}
return sequences;
}
console.log(' crayon!');

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