@effect-ts/system/_src/Testing/TestAspect/index.ts

Effect-TS is a zero dependency set of libraries to write highly productive, purely functional TypeScript at scale.

// ets_tracing: off

import type { ZSpec } from "../Spec/index.js"

export const TestAspectTypeId = Symbol.for("@effect-ts/system/Testing/TestAspect")
export type TestAspectTypeId = typeof TestAspectTypeId

export type ZSpecLB<R, E, LowerR> = ZSpec<R, E> & [LowerR] extends [R]
  ? ZSpec<R, E>
  : ZSpec<LowerR, E>

/**
 * A `TestAspect` is an aspect that can be weaved into specs. You can think of
 * an aspect as a polymorphic function, capable of transforming one test into
 * another, possibly enlarging the environment or error type.
 */
export interface TestAspect<LowerR, UpperR, LowerE, UpperE>
  extends TestAspectBase<LowerR, UpperR, LowerE, UpperE> {
  <R, E extends UpperE>(spec: ZSpecLB<R, E, LowerR>): ZSpec<R & UpperR, E | LowerE>
}

export interface TestAspectBase<LowerR, UpperR, LowerE, UpperE> {
  readonly [TestAspectTypeId]: TestAspectTypeId

  readonly some: (
    predicate: (s: string) => boolean
  ) => <R, E extends UpperE>(
    spec: ZSpecLB<R, E, LowerR>
  ) => ZSpec<R & UpperR, E | LowerE>
}

/**
 * Creates a test aspect by specify the some function
 */
export function aspect<LowerR, UpperR, LowerE, UpperE>(
  some: (
    predicate: (s: string) => boolean
  ) => <R, E extends UpperE>(
    spec: ZSpecLB<R, E, LowerR>
  ) => ZSpec<R & UpperR, E | LowerE>
): TestAspect<LowerR, UpperR, LowerE, UpperE> {
  const all: <R, E extends UpperE>(
    spec: ZSpecLB<R, E, LowerR>
  ) => ZSpec<R & UpperR, E | LowerE> = (spec) => some(() => true)(spec)

  return Object.assign(all, {
    [TestAspectTypeId]: TestAspectTypeId,
    some
  } as TestAspectBase<LowerR, UpperR, LowerE, UpperE>)
}

/**
 * An aspect that returns the tests unchanged
 */
export const identity: TestAspect<never, unknown, never, unknown> = aspect(
  () => (self) => self
)