如何使用.toPromise（）读取错误的请求（400）响应.catch（）

这是我的代码：

testConnection() {
    this.http.get(
      this.backendBaseUrl + `api/Test`, {observe: 'response'}
    ).toPromise()
    .then(response => {
      alert(`successfully.`);
    })
    .catch((error: HttpErrorResponse ) => {
      alert(`connection not successful:\n${error}`); // error.error, error.message => undefined
    });
  }

它仅作为错误请求提醒

Headers:

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Preview/ Response

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Alert

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更新：我想提醒预览/响应的响应，而不仅仅是错误的请求

Solved: Found the issue, was having a HttpInterceptor which was removing the error message

angular typescript