diff --git a/packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.test.ts b/packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.test.ts
index 6b6ef2eb13..45d23d9db2 100644
--- a/packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.test.ts
+++ b/packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.test.ts
@@ -50,17 +50,21 @@ describe('MockTranslationApi', () => {
       shallow: 'Foo {{ bar }}',
       multiple: 'Foo {{ bar }} {{ baz }}',
       deep: 'Foo {{ bar.baz }}',
-    });
+    } as const);
 
+    // @ts-expect-error
     expect(snapshot.t('shallow')).toBe('Foo {{ bar }}');
     expect(snapshot.t('shallow', { bar: 'Bar' })).toBe('Foo Bar');
 
+    // @ts-expect-error
     expect(snapshot.t('multiple')).toBe('Foo {{ bar }} {{ baz }}');
+    // @ts-expect-error
     expect(snapshot.t('multiple', { bar: 'Bar' })).toBe('Foo Bar {{ baz }}');
     expect(snapshot.t('multiple', { bar: 'Bar', baz: 'Baz' })).toBe(
       'Foo Bar Baz',
     );
 
+    // @ts-expect-error
     expect(snapshot.t('deep')).toBe('Foo {{ bar.baz }}');
     expect(snapshot.t('deep', { bar: { baz: 'Baz' } })).toBe('Foo Baz');
   });
@@ -69,7 +73,7 @@ describe('MockTranslationApi', () => {
   it('should not escape by default', () => {
     const snapshot = snapshotWithMessages({
       foo: 'Foo {{ foo }}',
-    });
+    } as const);
 
     expect(snapshot.t('foo', { foo: '<div>' })).toBe('Foo <div>');
     expect(
@@ -85,7 +89,7 @@ describe('MockTranslationApi', () => {
       foo: 'Foo $t(bar) $t(baz)',
       bar: 'Nested',
       baz: 'Baz {{ qux }}',
-    });
+    } as const);
 
     expect(snapshot.t('foo', { qux: 'Deep' })).toBe('Foo Nested Baz Deep');
   });
@@ -100,24 +104,36 @@ describe('MockTranslationApi', () => {
       relativeSecondsShort:
         '= {{ x, relativeTime(range: second; style: short) }}',
       list: '= {{ x, list }}',
-    });
+    } as const);
 
-    expect(snapshot.t('plain', { x: 5 })).toBe('= 5');
+    expect(snapshot.t('plain', { x: '5' })).toBe('= 5');
     expect(snapshot.t('number', { x: 5 })).toBe('= 5');
-    expect(snapshot.t('number', { x: 5, minimumFractionDigits: 1 })).toBe(
-      '= 5.0',
-    );
+    expect(
+      snapshot.t('number', {
+        x: 5,
+        formatParams: { x: { minimumFractionDigits: 1 } },
+      }),
+    ).toBe('= 5.0');
     expect(snapshot.t('numberFixed', { x: 5 })).toBe('= 5.00');
-    expect(snapshot.t('numberFixed', { x: 5, minimumFractionDigits: 3 })).toBe(
-      '= 5.000',
-    );
+    expect(
+      snapshot.t('numberFixed', {
+        x: 5,
+        formatParams: { x: { minimumFractionDigits: 3 } },
+      }),
+    ).toBe('= 5.000');
     expect(snapshot.t('relativeTime', { x: 3 })).toBe('= in 3 days');
     expect(snapshot.t('relativeTime', { x: -3 })).toBe('= 3 days ago');
-    expect(snapshot.t('relativeTime', { x: 15, range: 'weeks' })).toBe(
-      '= in 15 weeks',
-    );
     expect(
-      snapshot.t('relativeTime', { x: 15, range: 'weeks', style: 'short' }),
+      snapshot.t('relativeTime', {
+        x: 15,
+        formatParams: { x: { range: 'weeks' } },
+      }),
+    ).toBe('= in 15 weeks');
+    expect(
+      snapshot.t('relativeTime', {
+        x: 15,
+        formatParams: { x: { range: 'weeks', style: 'short' } },
+      }),
     ).toBe('= in 15 wk.');
     expect(snapshot.t('relativeSeconds', { x: 1 })).toBe('= in 1 second');
     expect(snapshot.t('relativeSeconds', { x: 2 })).toBe('= in 2 seconds');
@@ -138,14 +154,13 @@ describe('MockTranslationApi', () => {
       derp_other: 'derps',
       derpWithCount_one: '{{ count }} derp',
       derpWithCount_other: '{{ count }} derps',
-    });
+    } as const);
 
-    // TODO(Rugvip): Support plural keys
-    expect(snapshot.t('derp' as any, { count: 1 })).toBe('derp');
-    expect(snapshot.t('derp' as any, { count: 2 })).toBe('derps');
-    expect(snapshot.t('derp' as any, { count: 0 })).toBe('derps');
-    expect(snapshot.t('derpWithCount' as any, { count: 1 })).toBe('1 derp');
-    expect(snapshot.t('derpWithCount' as any, { count: 2 })).toBe('2 derps');
-    expect(snapshot.t('derpWithCount' as any, { count: 0 })).toBe('0 derps');
+    expect(snapshot.t('derp', { count: 1 })).toBe('derp');
+    expect(snapshot.t('derp', { count: 2 })).toBe('derps');
+    expect(snapshot.t('derp', { count: 0 })).toBe('derps');
+    expect(snapshot.t('derpWithCount', { count: 1 })).toBe('1 derp');
+    expect(snapshot.t('derpWithCount', { count: 2 })).toBe('2 derps');
+    expect(snapshot.t('derpWithCount', { count: 0 })).toBe('0 derps');
   });
 });
diff --git a/packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.ts b/packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.ts
index 0ffea6a1bd..608b634cc4 100644
--- a/packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.ts
+++ b/packages/test-utils/src/testUtils/apis/TranslationApi/MockTranslationApi.ts
@@ -16,6 +16,7 @@
 
 import {
   TranslationApi,
+  TranslationFunction,
   TranslationRef,
   TranslationSnapshot,
 } from '@backstage/core-plugin-api/alpha';
@@ -66,8 +67,6 @@ export class MockTranslationApi implements TranslationApi {
   ): TranslationSnapshot<TMessages> {
     const internalRef = toInternalTranslationRef(translationRef);
 
-    const t = this.#i18n.getFixedT(null, internalRef.id);
-
     if (!this.#registeredRefs.has(internalRef.id)) {
       this.#registeredRefs.add(internalRef.id);
       this.#i18n.addResourceBundle(
@@ -79,11 +78,14 @@ export class MockTranslationApi implements TranslationApi {
       );
     }
 
+    const t = this.#i18n.getFixedT(
+      null,
+      internalRef.id,
+    ) as TranslationFunction<TMessages>;
+
     return {
       ready: true,
-      t: (key, options) => {
-        return t(key as string, { ...options });
-      },
+      t,
     };
   }