diff --git a/src/core/classes/tests/database-table.test.ts b/src/core/classes/tests/database-table.test.ts
index 8e1e0f1e9..3b9c2bca2 100644
--- a/src/core/classes/tests/database-table.test.ts
+++ b/src/core/classes/tests/database-table.test.ts
@@ -63,7 +63,7 @@ function prepareStubs(config: Partial<CoreDatabaseConfiguration> = {}): [User[],
     });
     const table = new CoreDatabaseTableProxy<User>(config, database, 'users');
 
-    mockSingleton(CoreConfig, { isReady: () => Promise.resolve() });
+    mockSingleton(CoreConfig, { ready: () => Promise.resolve() });
 
     return [records, database, table];
 }
diff --git a/src/core/directives/tests/format-text.test.ts b/src/core/directives/tests/format-text.test.ts
index 0face19cd..265cd218a 100644
--- a/src/core/directives/tests/format-text.test.ts
+++ b/src/core/directives/tests/format-text.test.ts
@@ -33,7 +33,15 @@ describe('CoreFormatTextDirective', () => {
 
     beforeEach(() => {
         mockSingleton(CoreSites, { getSite: () => Promise.reject() });
-        mockSingleton(CoreConfig, { get: (_, defaultValue) => defaultValue });
+        mockSingleton(CoreConfig, {
+            get(name, defaultValue) {
+                if (defaultValue === undefined) {
+                    throw Error(`Default value not provided for '${name}'`);
+                }
+
+                return Promise.resolve(defaultValue);
+            },
+        });
         mockSingleton(CoreFilter, { formatText: text => Promise.resolve(text) });
         mockSingleton(CoreFilterHelper, { getFiltersAndFormatText: text => Promise.resolve({ text, filters: [] }) });
 
@@ -64,7 +72,7 @@ describe('CoreFormatTextDirective', () => {
 
     it('should format text', async () => {
         // Arrange
-        mockSingleton(CoreFilter, { formatText: () => 'Formatted text' });
+        mockSingleton(CoreFilter, { formatText: () => Promise.resolve('Formatted text') });
 
         // Act
         const { nativeElement } = await renderTemplate(
@@ -131,7 +139,7 @@ describe('CoreFormatTextDirective', () => {
         mockSingleton(CoreFilepool, { getSrcByUrl: () => Promise.resolve('file://local-path') });
         mockSingleton(CoreSites, {
             getSite: () => Promise.resolve(site),
-            getCurrentSite: () => Promise.resolve(site),
+            getCurrentSite: () => site,
         });
 
         // Act
diff --git a/src/core/services/tests/navigator.test.ts b/src/core/services/tests/navigator.test.ts
index 0433ecb0f..ff6b9f409 100644
--- a/src/core/services/tests/navigator.test.ts
+++ b/src/core/services/tests/navigator.test.ts
@@ -40,7 +40,7 @@ describe('CoreNavigator', () => {
 
         router = mockSingleton(Router, { url: '/' });
 
-        mockSingleton(CoreSites, { getCurrentSiteId: () => 42, isLoggedIn: () => true });
+        mockSingleton(CoreSites, { getCurrentSiteId: () => '42', isLoggedIn: () => true });
         mockSingleton(CoreMainMenu, { isMainMenuTab: path => Promise.resolve(currentMainMenuHandlers.includes(path)) });
     });
 
diff --git a/src/testing/utils.ts b/src/testing/utils.ts
index b4bad0c31..27e20a0b0 100644
--- a/src/testing/utils.ts
+++ b/src/testing/utils.ts
@@ -183,8 +183,7 @@ export function mock<T>(
     return instance as T;
 }
 
-export function mockSingleton<T>(singletonClass: CoreSingletonProxy<T>, instance: T): T;
-export function mockSingleton<T>(singletonClass: CoreSingletonProxy<unknown>, instance?: Record<string, unknown>): T;
+export function mockSingleton<T>(singletonClass: CoreSingletonProxy<T>, instance: T | Partial<T>): T;
 export function mockSingleton<T>(
     singletonClass: CoreSingletonProxy<unknown>,
     methods: string[],