♻️ Add reset() and tests (#1845)

Author: KATO-Hiro

src/lib/stores/active_contest_type.svelte.ts

@@ -50,6 +50,14 @@ export class ActiveContestTypeStore {
   isSame(contestType: ContestTableProviders): boolean {
     return this.value === contestType;
   }
+
+  /**
+   * Resets the active contest type to the default value.
+   * Sets the internal value to 'abcLatest20Rounds'.
+   */
+  reset(): void {
+    this.value = 'abcLatest20Rounds';
+  }
 }
 
 export const activeContestTypeStore = new ActiveContestTypeStore();

src/test/lib/stores/active_contest_type.svelte.test.ts

@@ -47,4 +47,21 @@ describe('ActiveContestTypeStore', () => {
     expect(store.isSame('abcLatest20Rounds' as ContestTableProviders)).toBe(false);
     expect(store.isSame('abc319Onwards' as ContestTableProviders)).toBe(false);
   });
+
+  test('expects to reset the value to default when calling reset()', () => {
+    // First change the value to something else
+    store.set('abc319Onwards' as ContestTableProviders);
+    expect(store.get()).toBe('abc319Onwards');
+
+    // Call reset and verify it goes back to default
+    store.reset();
+    expect(store.get()).toBe('abcLatest20Rounds');
+
+    // Change to a different value and reset again to verify consistency
+    store.set('fromAbc212ToAbc318' as ContestTableProviders);
+    expect(store.get()).toBe('fromAbc212ToAbc318');
+
+    store.reset();
+    expect(store.get()).toBe('abcLatest20Rounds');
+  });
 });