Fix ItemComponent no expectation tests

- renamed `showBackButton` to `showBackButton$` because it's an observable
- `showBackButton$` only emits `true` when the back button should be shown, it does not emit `false` when it should be hidden, it just did nothing

src/app/entity-groups/journal-entities/item-pages/journal-issue/journal-issue.component.html

@@ -1,4 +1,4 @@
-<ds-themed-results-back-button *ngIf="showBackButton | async" [back]="back"></ds-themed-results-back-button>
+<ds-themed-results-back-button *ngIf="showBackButton$ | async" [back]="back"></ds-themed-results-back-button>
 <div class="d-flex flex-row">
   <ds-themed-item-page-title-field [item]="object" class="mr-auto">
   </ds-themed-item-page-title-field>

src/app/entity-groups/journal-entities/item-pages/journal-volume/journal-volume.component.html

@@ -1,4 +1,4 @@
-<ds-themed-results-back-button *ngIf="showBackButton | async" [back]="back"></ds-themed-results-back-button>
+<ds-themed-results-back-button *ngIf="showBackButton$ | async" [back]="back"></ds-themed-results-back-button>
 <div class="d-flex flex-row">
   <ds-themed-item-page-title-field [item]="object" class="mr-auto">
   </ds-themed-item-page-title-field>

src/app/entity-groups/journal-entities/item-pages/journal/journal.component.html

@@ -1,4 +1,4 @@
-<ds-themed-results-back-button *ngIf="showBackButton | async" [back]="back"></ds-themed-results-back-button>
+<ds-themed-results-back-button *ngIf="showBackButton$ | async" [back]="back"></ds-themed-results-back-button>
 <div class="d-flex flex-row">
   <ds-themed-item-page-title-field [item]="object" class="mr-auto">
   </ds-themed-item-page-title-field>

src/app/entity-groups/research-entities/item-pages/org-unit/org-unit.component.html

@@ -1,4 +1,4 @@
-<ds-themed-results-back-button *ngIf="showBackButton | async" [back]="back"></ds-themed-results-back-button>
+<ds-themed-results-back-button *ngIf="showBackButton$ | async" [back]="back"></ds-themed-results-back-button>
 <div class="d-flex flex-row">
   <ds-themed-item-page-title-field [item]="object" class="mr-auto">
   </ds-themed-item-page-title-field>

src/app/entity-groups/research-entities/item-pages/person/person.component.html

@@ -1,4 +1,4 @@
-<ds-themed-results-back-button *ngIf="showBackButton | async" [back]="back"></ds-themed-results-back-button>
+<ds-themed-results-back-button *ngIf="showBackButton$ | async" [back]="back"></ds-themed-results-back-button>
 <div class="d-flex flex-row">
   <ds-themed-item-page-title-field class="mr-auto" [item]="object">
   </ds-themed-item-page-title-field>

src/app/entity-groups/research-entities/item-pages/project/project.component.html

@@ -1,4 +1,4 @@
-<ds-themed-results-back-button *ngIf="showBackButton | async" [back]="back"></ds-themed-results-back-button>
+<ds-themed-results-back-button *ngIf="showBackButton$ | async" [back]="back"></ds-themed-results-back-button>
 <div class="d-flex flex-row">
   <ds-themed-item-page-title-field [item]="object" class="mr-auto">
   </ds-themed-item-page-title-field>

src/app/item-page/simple/item-types/publication/publication.component.html

@@ -1,4 +1,4 @@
-<ds-themed-results-back-button *ngIf="showBackButton | async" [back]="back"></ds-themed-results-back-button>
+<ds-themed-results-back-button *ngIf="showBackButton$ | async" [back]="back"></ds-themed-results-back-button>
 <div class="row" *ngIf="iiifEnabled">
   <div class="col-12">
     <ds-mirador-viewer  id="iiif-viewer"

src/app/item-page/simple/item-types/shared/item.component.spec.ts

@@ -469,30 +469,31 @@ describe('ItemComponent', () => {
       fixture.detectChanges();
     }));
 
-    it('should hide back button',() => {
+    it('should hide back button', () => {
       spyOn(mockRouteService, 'getPreviousUrl').and.returnValue(observableOf('/item'));
-      comp.showBackButton.subscribe((val) => {
+      comp.ngOnInit();
+      comp.showBackButton$.subscribe((val) => {
         expect(val).toBeFalse();
       });
     });
     it('should show back button for search', () => {
       spyOn(mockRouteService, 'getPreviousUrl').and.returnValue(observableOf(searchUrl));
       comp.ngOnInit();
-      comp.showBackButton.subscribe((val) => {
+      comp.showBackButton$.subscribe((val) => {
         expect(val).toBeTrue();
       });
     });
     it('should show back button for browse', () => {
       spyOn(mockRouteService, 'getPreviousUrl').and.returnValue(observableOf(browseUrl));
       comp.ngOnInit();
-      comp.showBackButton.subscribe((val) => {
+      comp.showBackButton$.subscribe((val) => {
         expect(val).toBeTrue();
       });
     });
     it('should show back button for recent submissions', () => {
       spyOn(mockRouteService, 'getPreviousUrl').and.returnValue(observableOf(recentSubmissionsUrl));
       comp.ngOnInit();
-      comp.showBackButton.subscribe((val) => {
+      comp.showBackButton$.subscribe((val) => {
         expect(val).toBeTrue();
       });
     });

src/app/item-page/simple/item-types/shared/item.component.ts

@@ -5,7 +5,7 @@ import { getItemPageRoute } from '../../../item-page-routing-paths';
 import { RouteService } from '../../../../core/services/route.service';
 import { Observable } from 'rxjs';
 import { getDSpaceQuery, isIiifEnabled, isIiifSearchEnabled } from './item-iiif-utils';
-import { filter, map, take } from 'rxjs/operators';
+import { map, take } from 'rxjs/operators';
 import { Router } from '@angular/router';
 
 @Component({
@@ -27,7 +27,7 @@ export class ItemComponent implements OnInit {
   /**
    * Used to show or hide the back to results button in the view.
    */
-  showBackButton: Observable<boolean>;
+  showBackButton$: Observable<boolean>;
 
   /**
    * Route to the item page
@@ -73,10 +73,9 @@ export class ItemComponent implements OnInit {
 
     this.itemPageRoute = getItemPageRoute(this.object);
     // hide/show the back button
-    this.showBackButton = this.routeService.getPreviousUrl().pipe(
-      filter(url => this.previousRoute.test(url)),
+    this.showBackButton$ = this.routeService.getPreviousUrl().pipe(
+      map((url: string) => this.previousRoute.test(url)),
       take(1),
-      map(() => true)
     );
     // check to see if iiif viewer is required.
     this.iiifEnabled = isIiifEnabled(this.object);

src/app/item-page/simple/item-types/untyped-item/untyped-item.component.html

@@ -1,4 +1,4 @@
-<ds-themed-results-back-button *ngIf="showBackButton | async" [back]="back"></ds-themed-results-back-button>
+<ds-themed-results-back-button *ngIf="showBackButton$ | async" [back]="back"></ds-themed-results-back-button>
 <div class="row" *ngIf="iiifEnabled">
   <div class="col-12">
     <ds-mirador-viewer id="iiif-viewer"