diff --git a/packages/angular-query-experimental/src/__tests__/inject-query.test-d.ts b/packages/angular-query-experimental/src/__tests__/inject-query.test-d.ts
index 8b92c0120f..a49ca421cf 100644
--- a/packages/angular-query-experimental/src/__tests__/inject-query.test-d.ts
+++ b/packages/angular-query-experimental/src/__tests__/inject-query.test-d.ts
@@ -1,8 +1,125 @@
-import { describe, expectTypeOf } from 'vitest'
-import { injectQuery } from '..'
+import { describe, expectTypeOf, it } from 'vitest'
+import { injectQuery, queryOptions } from '..'
 import { simpleFetcher } from './test-utils'
 import type { Signal } from '@angular/core'
 
+describe('initialData', () => {
+  describe('Config object overload', () => {
+    it('TData should always be defined when initialData is provided as an object', () => {
+      const { data } = injectQuery(() => ({
+        queryKey: ['key'],
+        queryFn: () => ({ wow: true }),
+        initialData: { wow: true },
+      }))
+
+      expectTypeOf(data).toEqualTypeOf<Signal<{ wow: boolean }>>()
+    })
+
+    it('TData should be defined when passed through queryOptions', () => {
+      const options = () =>
+        queryOptions({
+          queryKey: ['key'],
+          queryFn: () => {
+            return {
+              wow: true,
+            }
+          },
+          initialData: {
+            wow: true,
+          },
+        })
+      const { data } = injectQuery(options)
+
+      expectTypeOf(data).toEqualTypeOf<Signal<{ wow: boolean }>>()
+    })
+
+    it('should be possible to define a different TData than TQueryFnData using select with queryOptions spread into useQuery', () => {
+      const options = queryOptions({
+        queryKey: ['key'],
+        queryFn: () => Promise.resolve(1),
+      })
+
+      const query = injectQuery(() => ({
+        ...options,
+        select: (data) => data > 1,
+      }))
+
+      expectTypeOf(query.data).toEqualTypeOf<Signal<boolean | undefined>>()
+    })
+
+    it('TData should always be defined when initialData is provided as a function which ALWAYS returns the data', () => {
+      const { data } = injectQuery(() => ({
+        queryKey: ['key'],
+        queryFn: () => {
+          return {
+            wow: true,
+          }
+        },
+        initialData: () => ({
+          wow: true,
+        }),
+      }))
+
+      expectTypeOf(data).toEqualTypeOf<Signal<{ wow: boolean }>>()
+    })
+
+    it('TData should have undefined in the union when initialData is NOT provided', () => {
+      const { data } = injectQuery(() => ({
+        queryKey: ['key'],
+        queryFn: () => {
+          return {
+            wow: true,
+          }
+        },
+      }))
+
+      expectTypeOf(data).toEqualTypeOf<Signal<{ wow: boolean } | undefined>>()
+    })
+
+    it('TData should have undefined in the union when initialData is provided as a function which can return undefined', () => {
+      const { data } = injectQuery(() => ({
+        queryKey: ['key'],
+        queryFn: () => {
+          return {
+            wow: true,
+          }
+        },
+        initialData: () => undefined as { wow: boolean } | undefined,
+      }))
+
+      expectTypeOf(data).toEqualTypeOf<Signal<{ wow: boolean } | undefined>>()
+    })
+
+    it('TData should be narrowed after an isSuccess check when initialData is provided as a function which can return undefined', () => {
+      const query = injectQuery(() => ({
+        queryKey: ['key'],
+        queryFn: () => {
+          return {
+            wow: true,
+          }
+        },
+        initialData: () => undefined as { wow: boolean } | undefined,
+      }))
+
+      if (query.isSuccess()) {
+        expectTypeOf(query.data).toEqualTypeOf<Signal<{ wow: boolean }>>()
+      }
+    })
+  })
+
+  describe('structuralSharing', () => {
+    it('should restrict to same types', () => {
+      injectQuery(() => ({
+        queryKey: ['key'],
+        queryFn: () => 5,
+        structuralSharing: (_oldData, newData) => {
+          return newData
+        },
+      }))
+    })
+  })
+})
+
 describe('Discriminated union return type', () => {
   test('data should be possibly undefined by default', () => {
     const query = injectQuery(() => ({