node/test/parallel/test-streams-highwatermark.js

'use strict';
const common = require('../common');

const assert = require('assert');
const stream = require('stream');

{
  // This test ensures that the stream implementation correctly handles values
  // for highWaterMark which exceed the range of signed 32 bit integers and
  // rejects invalid values.

  // This number exceeds the range of 32 bit integer arithmetic but should still
  // be handled correctly.
  const ovfl = Number.MAX_SAFE_INTEGER;

  const readable = stream.Readable({ highWaterMark: ovfl });
  assert.strictEqual(readable._readableState.highWaterMark, ovfl);

  const writable = stream.Writable({ highWaterMark: ovfl });
  assert.strictEqual(writable._writableState.highWaterMark, ovfl);

  for (const invalidHwm of [true, false, '5', {}, -5, NaN]) {
    for (const type of [stream.Readable, stream.Writable]) {
      common.expectsError(() => {
        type({ highWaterMark: invalidHwm });
      }, {
        type: TypeError,
        code: 'ERR_INVALID_OPT_VALUE',
        message:
          `The value "${invalidHwm}" is invalid for option "highWaterMark"`
      });
    }
  }
}

{
  // This test ensures that the push method's implementation
  // correctly handles the edge case where the highWaterMark and
  // the state.length are both zero

  const readable = stream.Readable({ highWaterMark: 0 });

  for (let i = 0; i < 3; i++) {
    const needMoreData = readable.push();
    assert.strictEqual(needMoreData, true);
  }
}

{
  // This test ensures that the read(n) method's implementation
  // correctly handles the edge case where the highWaterMark, state.length
  // and n are all zero

  const readable = stream.Readable({ highWaterMark: 0 });

  readable._read = common.mustCall();
  readable.read(0);
}