How to mock blob response from API in Angular test case

Question

In my angular application, I have a REST API call which returns me a Blob data which is eventually opened in a new tab. I am trying to create a mock Blob object in my jasmine testcase and spyon the service call and return the Blob. I am not able to assign it to the response and cannot validate my mock blob.

spec.ts

it('should call open doc ', () => {        
    spyOn<any>(component['docService'], 'getDoc');
    component['getDOC']('mypdf');
    let obj  = Object({ responseType: 'blob' });       
    component['docService']['getResponse'] = obj;
    expect(component['docServicee']['getDoc']).toHaveBeenCalled();
});

component.ts

public getDOC(file: string): void {
    this.docService.getDoc('mypdf); 
    this.docService.getResponse.subscribe((response) => {
        if (response) { // Test case not covered
            // open the file 
        }
    });      
}

DocService.ts

public getDoc(val): void {
        apiEndpointcall.subscribe({
        next: (res: Blob) => {
        
        },
        error: (error: Error) => {
          
        }
    });
}