ways to use Jest's test.each

jest-test-each.spec.js

describe("ways to use Jest's test.each", () => {


  test.each([
    [1, 1, 2],
    [1, 2, 3],
    [2, 1, 3],
  ])('.add(%i, %i)', (a, b, expected) => {
    expect(a + b).toBe(expected)
  })
  // => ✅ prints:
  // ✓ .add(1, 1)
  // ✓ .add(1, 2)
  // ✓ .add(2, 1)

  test.each([
    { a: 1, b: 1, expected: 2 },
    { a: 1, b: 2, expected: 3 },
    { a: 2, b: 1, expected: 3 },
  ])('.add($a, $b)', ({ a, b, expected }) => {
    expect(a + b).toBe(expected)
  })
  // => ❌ does not replace $a by value

  test.each([
    { a: 1, b: 1, expected: 2 },
    { a: 1, b: 2, expected: 3 },
    { a: 2, b: 1, expected: 3 },
  ])('.add(%o)', ({ a, b, expected }) => {
    expect(a + b).toBe(expected)
  })
  // => ✅ prints:
  // ✓ .add({ a: 1, b: 1, expected: 2 })
  // ✓ .add({ a: 1, b: 2, expected: 3 })
  // ✓ .add({ a: 2, b: 1, expected: 3 })

  test.each`
    a    | b    | expected
    ${1} | ${1} | ${2}
    ${1} | ${2} | ${3}
    ${2} | ${1} | ${3}
  `('returns $expected when $a is added to $b', ({ a, b, expected }) => {
    expect(a + b).toBe(expected)
  })
  // => ✅ prints:
  // ✓ returns 2 when 1 is added to 1
  // ✓ returns 3 when 1 is added to 2
  // ✓ returns 3 when 2 is added to 1

})