Snapshot testing

[dsseng]

Add .toMatchSnapshot() matcher to testing module

[j-f1]

What should the format be? Jest uses a CommonJS-inspired format, so here’s a few suggestions:

// test code
test(function doThingA() {
  assertMatchesSnaphot(foo)
})
test({
  name: 'do thing B',
  fn() {
    assertMatchesSnaphot(foo)
  }
})

// option 1
import 'https://deno.land/std/testing/snapshot/v1.ts'
export default {
  doThingA: [`blah blah`],
  'do thing B': [`blah blah`]
}

// option 2
import 'https://deno.land/std/testing/snapshot/v1.ts' 

export const doThingA = [`blah blah`]
export const do__thing__B = [`blah blah`]

[dsseng]

@j-f1 look at jest

[j-f1]

Jest uses this format:

// Jest Snapshot v1, https://goo.gl/fbAQLP

[ if the snapshot is single-line ]
exports[`test name here 1`] = `foo`

[ if the snapshot is multiline ]
exports[`test name here 2`] = `
foo
bar
`

My two snapshot proposals alter this in a few ways:

1. Instead of using an implict comment, an explicit import is used.
2. Instead of creating multiple snapshots for each test with repetitions of the test name, I use an array.
3. ESM is used instead of CommonJS

[j-f1]

Here’s another proposal: eschew the JS format altogether

Deno snapshot v1, https://deno.land/std/testing/snapshot/v1.md

snapshot `test name here` [`
  foo
`, `
  foo
  bar
`]

snapshot `another test` [`foo`, `foo bar`]