assert.equal(0/0, 0/0) fails despite both being NaN

[balupton]

• Version: v12.12.0
• Platform: Darwin balupton-macbook.local 19.0.0 Darwin Kernel Version 19.0.0: Thu Oct 17 16:17:15 PDT 2019; root:xnu-6153.41.3~29/RELEASE_X86_64 x86_64
• Subsystem: 64-bit

const assert = require('assert')
function log(fn) {
	try {
		fn()
	} catch (e) {
		console.error('---')
		console.error(fn.toString())
		console.error(e)
		console.error('\n')
	}
}

// nan value
log(() => assert.equal(0 / 0, 0 / 0))
log(() => assert.deepEqual(0 / 0, 0 / 0))

// nan reference
const nan = 0 / 0
log(() => assert.equal(nan, nan))
log(() => assert.deepEqual(nan, nan))

// object value
log(() => assert.deepEqual({ p: nan }, { p: nan }))

// object reference
const o = { p: nan }
log(() => assert.equal(o, o))
log(() => assert.deepEqual(o, o))

---
() => assert.equal(0 / 0, 0 / 0)
AssertionError [ERR_ASSERTION]: NaN == NaN
    at /Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:14:18
    at log (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:4:3)
    at Object.<anonymous> (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:14:1)
    at Module._compile (internal/modules/cjs/loader.js:956:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:973:10)
    at Module.load (internal/modules/cjs/loader.js:812:32)
    at Function.Module._load (internal/modules/cjs/loader.js:724:14)
    at Function.Module.runMain (internal/modules/cjs/loader.js:1025:10)
    at internal/main/run_main_module.js:17:11 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: NaN,
  expected: NaN,
  operator: '=='
}


---
() => assert.deepEqual(0 / 0, 0 / 0)
AssertionError [ERR_ASSERTION]: Expected values to be loosely deep-equal:

NaN

should loosely deep-equal

NaN
    at /Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:15:18
    at log (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:4:3)
    at Object.<anonymous> (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:15:1)
    at Module._compile (internal/modules/cjs/loader.js:956:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:973:10)
    at Module.load (internal/modules/cjs/loader.js:812:32)
    at Function.Module._load (internal/modules/cjs/loader.js:724:14)
    at Function.Module.runMain (internal/modules/cjs/loader.js:1025:10)
    at internal/main/run_main_module.js:17:11 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: NaN,
  expected: NaN,
  operator: 'deepEqual'
}


---
() => assert.equal(nan, nan)
AssertionError [ERR_ASSERTION]: NaN == NaN
    at /Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:19:18
    at log (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:4:3)
    at Object.<anonymous> (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:19:1)
    at Module._compile (internal/modules/cjs/loader.js:956:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:973:10)
    at Module.load (internal/modules/cjs/loader.js:812:32)
    at Function.Module._load (internal/modules/cjs/loader.js:724:14)
    at Function.Module.runMain (internal/modules/cjs/loader.js:1025:10)
    at internal/main/run_main_module.js:17:11 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: NaN,
  expected: NaN,
  operator: '=='
}


---
() => assert.deepEqual(nan, nan)
AssertionError [ERR_ASSERTION]: Expected values to be loosely deep-equal:

NaN

should loosely deep-equal

NaN
    at /Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:20:18
    at log (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:4:3)
    at Object.<anonymous> (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:20:1)
    at Module._compile (internal/modules/cjs/loader.js:956:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:973:10)
    at Module.load (internal/modules/cjs/loader.js:812:32)
    at Function.Module._load (internal/modules/cjs/loader.js:724:14)
    at Function.Module.runMain (internal/modules/cjs/loader.js:1025:10)
    at internal/main/run_main_module.js:17:11 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: NaN,
  expected: NaN,
  operator: 'deepEqual'
}


---
() => assert.deepEqual({ p: nan }, { p: nan })
AssertionError [ERR_ASSERTION]: Expected values to be loosely deep-equal:

{
  p: NaN
}

should loosely deep-equal

{
  p: NaN
}
    at /Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:23:18
    at log (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:4:3)
    at Object.<anonymous> (/Users/balupton/Projects/batches/obligations/promises/normalify/node-issue-30350.js:23:1)
    at Module._compile (internal/modules/cjs/loader.js:956:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:973:10)
    at Module.load (internal/modules/cjs/loader.js:812:32)
    at Function.Module._load (internal/modules/cjs/loader.js:724:14)
    at Function.Module.runMain (internal/modules/cjs/loader.js:1025:10)
    at internal/main/run_main_module.js:17:11 {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: [Object],
  expected: [Object],
  operator: 'deepEqual'
}

[targos]

assert.equal uses the == operator to compare values.
In JavaScript, this operator always returns false with NaN.
We recommend to use assert.strictEqual instead, which handles NaN as you would like.

[balupton]

ok thanks

[addaleax]

I do feel like assert.equal() should never fail when assert.strictEqual() succeeds, though?