node/test/simple/test-fs-watch-file.js

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var common = require('../common');
var assert = require('assert');
var path = require('path');
var fs = require('fs');


var filename = path.join(common.fixturesDir, 'watch.txt');
fs.writeFileSync(filename, "hello");

assert.throws(
  function() {
    fs.watchFile(filename);
  },
  function(e) {
    return e.message === 'watchFile requires a listener function';
  }
);

assert.doesNotThrow(
  function() {
    fs.watchFile(filename, function(curr, prev) {
      fs.unwatchFile(filename);
      fs.unlinkSync(filename);
    });
  }
);

setTimeout(function() {
  fs.writeFileSync(filename, "world");
}, 1000);