Angular Unit test of pipe transfome type string[]

I trying to make test unit for this pipe with angular/typeScript:

@Pipe({
  name: 'getCausesFromListCountDailyDelay'
})
export class GetCausesFromListCountDailyDelayPipe implements PipeTransform {
  transform(listCountDailyDelay: ListCountDelay[]): string[] {
    return listCountDailyDelay.map(count => count.cause.charAt(0) + '     ' + count.totalTime);
  }
}

and when I eecute the test I have problem

error TS2339: Property 'toEqual' does not exist on type 'string[]

my test file :

 it('should GetCausesFromListCountDailyDelayPipe', () => {
    const listCountDailyDelay: ListCountDelay[] = [
      {
        centre: 'LFAF',
        cause: 'CCCC',
        totalTime: 5
      },
      {
        centre: 'LFFF',
        cause: 'IIII',
        totalTime: 20
      },
      {
        centre: 'LFF',
        cause: 'FHHH',
        totalTime: 10
      },
    ];
    const resultDatas: ListCountDelay[] = [
      {
        centre: 'LFAF',
        cause: 'C    ',
        totalTime: 5
      },
      {
        centre: 'LFFF',
        cause: 'I    ',
        totalTime: 20
      },
      {
        centre: 'LFF',
        cause: 'F    ',
        totalTime: 10
      },
    ];

    expect(pipe.transform(listCountDailyDelay).toEqual(resultDatas));
  });

the pipe transform return type string[] but I can not do this test with Equal or toBe !!! any idea please ?!!