test: check range fix for slowToString

Verify that start and end are coerced properly.

Ref: #2919
PR-URL: #4019
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

test/parallel/test-buffer.js

@@ -248,14 +248,83 @@ b.copy(new Buffer(1), 1, 1, 1);
 // try to copy 0 bytes from past the end of the source buffer
 b.copy(new Buffer(1), 0, 2048, 2048);
 
-// try to toString() a 0-length slice of a buffer, both within and without the
-// valid buffer range
-assert.equal(new Buffer('abc').toString('ascii', 0, 0), '');
-assert.equal(new Buffer('abc').toString('ascii', -100, -100), '');
-assert.equal(new Buffer('abc').toString('ascii', 100, 100), '');
+const rangeBuffer = new Buffer('abc');
+
+// if start >= buffer's length, empty string will be returned
+assert.equal(rangeBuffer.toString('ascii', 3), '');
+assert.equal(rangeBuffer.toString('ascii', +Infinity), '');
+assert.equal(rangeBuffer.toString('ascii', 3.14, 3), '');
+assert.equal(rangeBuffer.toString('ascii', 'Infinity', 3), '');
+
+// if end <= 0, empty string will be returned
+assert.equal(rangeBuffer.toString('ascii', 1, 0), '');
+assert.equal(rangeBuffer.toString('ascii', 1, -1.2), '');
+assert.equal(rangeBuffer.toString('ascii', 1, -100), '');
+assert.equal(rangeBuffer.toString('ascii', 1, -Infinity), '');
+
+// if start < 0, start will be taken as zero
+assert.equal(rangeBuffer.toString('ascii', -1, 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', -1.99, 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', -Infinity, 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', '-1', 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', '-1.99', 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', '-Infinity', 3), 'abc');
+
+// if start is an invalid integer, start will be taken as zero
+assert.equal(rangeBuffer.toString('ascii', 'node.js', 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', {}, 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', [], 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', NaN, 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', null, 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', undefined, 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', false, 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', '', 3), 'abc');
+
+// but, if start is an integer when coerced, then it will be coerced and used.
+assert.equal(rangeBuffer.toString('ascii', '-1', 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', '1', 3), 'bc');
+assert.equal(rangeBuffer.toString('ascii', '-Infinity', 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', '3', 3), '');
+assert.equal(rangeBuffer.toString('ascii', Number(3), 3), '');
+assert.equal(rangeBuffer.toString('ascii', '3.14', 3), '');
+assert.equal(rangeBuffer.toString('ascii', '1.99', 3), 'bc');
+assert.equal(rangeBuffer.toString('ascii', '-1.99', 3), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 1.99, 3), 'bc');
+assert.equal(rangeBuffer.toString('ascii', true, 3), 'bc');
+
+// if end > buffer's length, end will be taken as buffer's length
+assert.equal(rangeBuffer.toString('ascii', 0, 5), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, 6.99), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, Infinity), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, '5'), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, '6.99'), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, 'Infinity'), 'abc');
+
+// if end is an invalid integer, end will be taken as buffer's length
+assert.equal(rangeBuffer.toString('ascii', 0, 'node.js'), '');
+assert.equal(rangeBuffer.toString('ascii', 0, {}), '');
+assert.equal(rangeBuffer.toString('ascii', 0, NaN), '');
+assert.equal(rangeBuffer.toString('ascii', 0, undefined), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, null), '');
+assert.equal(rangeBuffer.toString('ascii', 0, []), '');
+assert.equal(rangeBuffer.toString('ascii', 0, false), '');
+assert.equal(rangeBuffer.toString('ascii', 0, ''), '');
+
+// but, if end is an integer when coerced, then it will be coerced and used.
+assert.equal(rangeBuffer.toString('ascii', 0, '-1'), '');
+assert.equal(rangeBuffer.toString('ascii', 0, '1'), 'a');
+assert.equal(rangeBuffer.toString('ascii', 0, '-Infinity'), '');
+assert.equal(rangeBuffer.toString('ascii', 0, '3'), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, Number(3)), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, '3.14'), 'abc');
+assert.equal(rangeBuffer.toString('ascii', 0, '1.99'), 'a');
+assert.equal(rangeBuffer.toString('ascii', 0, '-1.99'), '');
+assert.equal(rangeBuffer.toString('ascii', 0, 1.99), 'a');
+assert.equal(rangeBuffer.toString('ascii', 0, true), 'a');
 
 // try toString() with a object as a encoding
-assert.equal(new Buffer('abc').toString({toString: function() {
+assert.equal(rangeBuffer.toString({toString: function() {
   return 'ascii';
 }}), 'abc');