Function diffLaws

packages/effect/test/Differ.test.ts:5–58

(
  differ: Differ.Differ<Value, Patch>,
  gen: () => Value,
  equal: (a: Value, b: Value) => boolean
)

import { Array as Arr, Chunk, Differ, Equal, HashMap, HashSet, pipe } from "effect"

function diffLaws<Value, Patch>(
  differ: Differ.Differ<Value, Patch>,
  gen: () => Value,
  equal: (a: Value, b: Value) => boolean
): void {
  const it = (name: string, f: () => void) =>
    it_(name, () => {
      for (let i = 0; i < 100; i++) {
        f()
      }
    })

  describe("differ laws", () => {
    it("combining patches is associative", () => {
      const value1 = gen()
      const value2 = gen()
      const value3 = gen()
      const value4 = gen()
      const patch1 = differ.diff(value1, value2)
      const patch2 = differ.diff(value2, value3)
      const patch3 = differ.diff(value3, value4)
      const left = differ.combine(differ.combine(patch1, patch2), patch3)
      const right = differ.combine(patch1, differ.combine(patch2, patch3))
      assertTrue(equal(differ.patch(left, value1), differ.patch(right, value1)))
    })

    it("combining a patch with an empty patch is an identity", () => {
      const oldValue = gen()
      const newValue = gen()
      const patch = differ.diff(oldValue, newValue)
      const left = differ.combine(patch, differ.empty)
      const right = differ.combine(differ.empty, patch)
      assertTrue(equal(differ.patch(left, oldValue), newValue))
      assertTrue(equal(differ.patch(right, oldValue), newValue))
    })

    it("diffing a value with itself returns an empty patch", () => {
      const value = gen()
      deepStrictEqual(differ.diff(value, value), differ.empty)
    })

    it("diffing and then patching is an identity", () => {
      const oldValue = gen()
      const newValue = gen()
      const patch = differ.diff(oldValue, newValue)
      assertTrue(equal(differ.patch(patch, oldValue), newValue))
    })

    it("patching with an empty patch is an identity", () => {
      const value = gen()
      assertTrue(equal(differ.patch(differ.empty, value), value))
    })
  })
}

const min = 1
const max = 100