flow like the river

VISUALIZACION/node_modules/crypto-browserify/test/random-fill.js

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+var test = require('tape')
+var crypto = require('../')
+var Buffer = require('safe-buffer').Buffer
+
+test('get error message', function (t) {
+  try {
+    var b = crypto.randomFillSync(Buffer.alloc(10))
+    t.ok(Buffer.isBuffer(b))
+    t.end()
+  } catch (err) {
+    t.ok(/not supported/.test(err.message), '"not supported"  is in error message')
+    t.end()
+  }
+})
+
+test('randomfill', function (t) {
+  t.plan(5)
+  t.equal(crypto.randomFillSync(Buffer.alloc(10)).length, 10)
+  t.ok(Buffer.isBuffer(crypto.randomFillSync(Buffer.alloc(10))))
+  crypto.randomFill(Buffer.alloc(10), function (ex, bytes) {
+    t.error(ex)
+    t.equal(bytes.length, 10)
+    t.ok(Buffer.isBuffer(bytes))
+    t.end()
+  })
+})
+
+test('seems random', function (t) {
+  var L = 1000
+  var b = crypto.randomFillSync(Buffer.alloc(L))
+
+  var mean = [].reduce.call(b, function (a, b) {
+    return a + b
+  }, 0) / L
+
+  // test that the random numbers are plausably random.
+  // Math.random() will pass this, but this will catch
+  // terrible mistakes such as this blunder:
+  // https://github.com/dominictarr/crypto-browserify/commit/3267955e1df7edd1680e52aeede9a89506ed2464#commitcomment-7916835
+
+  // this doesn't check that the bytes are in a random *order*
+  // but it's better than nothing.
+
+  var expected = 256 / 2
+  var smean = Math.sqrt(mean)
+
+  // console.log doesn't work right on testling, *grumble grumble*
+  console.log(JSON.stringify([expected - smean, mean, expected + smean]))
+  t.ok(mean < expected + smean)
+  t.ok(mean > expected - smean)
+
+  t.end()
+})