Fix searching/filtering bugs #235

- Fix a bug (introduced in 1b9be8fe) preventing the tree view from being
  visible during a search.
- Fix a minor bug where the scripts view does not render based on the
  initial filter.
- Add Vue component tests for `TheScriptView` to prevent regressions.
- Refactor `isSearching` in `TheScriptView` to simplify its logic.

tests/unit/shared/Stubs/CategoryCollectionStateStub.ts

@@ -17,7 +17,7 @@ export class CategoryCollectionStateStub implements ICategoryCollectionState {
 
   public readonly code: IApplicationCode = new ApplicationCodeStub();
 
-  public readonly filter: IUserFilter = new UserFilterStub();
+  public filter: IUserFilter = new UserFilterStub();
 
   public get os(): OperatingSystem {
     return this.collectionStub.os;
@@ -42,6 +42,11 @@ export class CategoryCollectionStateStub implements ICategoryCollectionState {
     return this;
   }
 
+  public withFilter(filter: IUserFilter) {
+    this.filter = filter;
+    return this;
+  }
+
   public withSelectedScripts(initialScripts: readonly SelectedScript[]) {
     this.selection.withSelectedScripts(initialScripts);
     return this;