api-client-testing

API Client Testing Patterns

Required Imports for API Client Tests

import { describe, expect, it } from '@effect/vitest'
import { FetchHttpClientTest, getExitError } from '@t6c/lib-api'
import { Effect as E, Exit } from 'effect'
import { MockConfigLayer } from '../config.js'

Standard API Client Test Structure

Success Test Pattern

it.effect('should [action description]', () =>
  E.gen(function* () {
    const service = yield* ServiceName
    const result = yield* service.methodName(params)

    expect(result).toEqual(expectedResult)
  }).pipe(
    E.provide(ServiceName.DefaultWithoutDependencies),
    E.provide(
      FetchHttpClientTest(
        new Response(JSON.stringify(mockResponse), { status: 200 }),
      ),
    ),
    E.provide(MockConfigLayer),
  ),
)

Error Test Pattern (PREFERRED)

it.effect('should handle [error type]', () =>
  E.gen(function* () {
    const service = yield* ServiceName
    const result = yield* service
      .methodName(params)
      .pipe(E.exit)

    expect(Exit.isFailure(result)).toBe(true)
    const error = getExitError(result)
    expect(error?._tag).toBe('ExpectedErrorType')
  }).pipe(
    E.provide(ServiceName.DefaultWithoutDependencies),
    E.provide(FetchHttpClientTest(new Response(null, { status: 404 }))),
    E.provide(MockConfigLayer),
  ),
)

Variable Scoping Rules

CRITICAL: Variables Used in FetchHttpClientTest

• ALWAYS declare variables outside the generator function if they're used in FetchHttpClientTest
• This prevents scoping issues where variables are not accessible

// ✅ CORRECT
it.effect('should update resource', () => {
  const updatedResource = { ...mockResource, field: 'new value' }
  
  return E.gen(function* () {
    const service = yield* ServiceName
    const result = yield* service.update(id, updates)
    expect(result).toEqual(updatedResource)
  }).pipe(
    E.provide(ServiceName.DefaultWithoutDependencies),
    E.provide(
      FetchHttpClientTest(
        new Response(JSON.stringify(updatedResource), { status: 200 }),
      ),
    ),
    E.provide(MockConfigLayer),
  )
})

// ❌ WRONG - Variable not accessible in FetchHttpClientTest
it.effect('should update resource', () =>
  E.gen(function* () {
    const updatedResource = { /* ... */ } // Scoping issue!
    // ...
  }).pipe(
    E.provide(
      FetchHttpClientTest(
        new Response(JSON.stringify(updatedResource), { status: 200 }), // Error!
      ),
    ),
  ),
)