Struggling to Mock Methods for Testing `postMessage` in MessageService

imports....

@Injectable()
export class MessageService {
  private readonly logger = new LoggerService('messageService')

  postMessage({
    title,
    body,
    tags,
    webhookURL,
  }: {
    title: string
    body: string
    tags: string
    webhookURL: string
  }): EF.Effect<void, HttpClientError.HttpClientError, never> {
    return EF.gen(this, function* () {
      const message = `### ${title}\n\n
${body}\n
**When:** ${this.getFormattedTime(DateTime.unsafeNow())}\n
**Environment:** ${this.getCurrentEnvironment()}\n
**Tags:** ${tags}\n`

      yield* pipe(
        HttpClientRequest.post(webhookURL),
        HttpClientRequest.setHeader('Content-Type', 'application/json'),
        HttpClientRequest.unsafeJsonBody({ text: message }),
        HttpClient.fetchOk,
        EF.scoped,
        EF.tapBoth({
          onSuccess: () =>
            EF.sync(() => this.logger.info('[MessageService: postMessage]: Message was sent.')),
          onFailure: (error) =>
            EF.sync(() =>
              this.logger.error(
                '[MessageService: postMessage]: Error while posting message',
                { error, message }
              )
            ),
        })
      )
    })
  }

  getFormattedTime(date: DateTime.Utc): string {
    return pipe(date, DateTime.formatUtc({ dateStyle: 'medium', timeStyle: 'short' }))
  }

  getCurrentEnvironment = (): string => {
    return pipe(
      getSSMParameter('APP_ROOT_DOMAIN'),
      S.split('.sella'),
      A.head,
      O.getOrElse(() => "Couldn't get environment")
    )
  }
}