diff --git a/packages/query-core/src/__tests__/mutation.test-d.tsx b/packages/query-core/src/__tests__/mutation.test-d.tsx
index 49397c39629..55ed9cea967 100644
--- a/packages/query-core/src/__tests__/mutation.test-d.tsx
+++ b/packages/query-core/src/__tests__/mutation.test-d.tsx
@@ -1,6 +1,7 @@
 import { describe, expectTypeOf, it } from 'vitest'
 import { QueryClient } from '../queryClient'
 import { MutationObserver } from '../mutationObserver'
+import type { DefaultError, MutateFunction, MutateOptions } from '../types'
 
 describe('mutation', () => {
   describe('onMutate', () => {
@@ -93,4 +94,241 @@ describe('mutation', () => {
       })
     })
   })
+
+  describe('MutateFunction', () => {
+    it('void variables', () => {
+      const mutate = {} as MutateFunction
+
+      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
+        undefined | void
+      >()
+
+      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+        undefined | MutateOptions<unknown, DefaultError, void, unknown>
+      >()
+
+      mutate() // can be called with no arguments
+      mutate(undefined, {
+        onError: (e) => {
+          expectTypeOf(e).toEqualTypeOf<DefaultError>()
+        },
+      })
+    })
+
+    it('optional undefinable variables', () => {
+      const mutate = {} as MutateFunction<
+        unknown,
+        DefaultError,
+        number | undefined,
+        unknown
+      >
+
+      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
+        number | undefined
+      >()
+
+      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+        | undefined
+        | MutateOptions<unknown, DefaultError, number | undefined, unknown>
+      >()
+
+      mutate() // can be called with no arguments
+      mutate(undefined, {
+        onError: (e) => {
+          expectTypeOf(e).toEqualTypeOf<DefaultError>()
+        },
+      })
+    })
+
+    it('unknown variables', () => {
+      const mutate = {} as MutateFunction<
+        unknown,
+        DefaultError,
+        unknown,
+        unknown
+      >
+
+      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<unknown>()
+
+      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+        undefined | MutateOptions<unknown, DefaultError, unknown, unknown>
+      >()
+
+      mutate() // can be called with no arguments
+    })
+
+    it('any variables', () => {
+      const mutate = {} as MutateFunction<unknown, DefaultError, any, unknown>
+
+      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<any>()
+
+      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+        undefined | MutateOptions<unknown, DefaultError, any, unknown>
+      >()
+
+      mutate() // can be called with no arguments
+    })
+
+    it('void union variables', () => {
+      const mutate = {} as MutateFunction<
+        unknown,
+        DefaultError,
+        void | string,
+        unknown
+      >
+
+      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
+        void | string | undefined
+      >()
+
+      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+        undefined | MutateOptions<unknown, DefaultError, void | string, unknown>
+      >()
+
+      mutate() // can be called with no arguments
+    })
+
+    it('required non-undefinable variables', () => {
+      const mutate = {} as MutateFunction<
+        unknown,
+        DefaultError,
+        number,
+        unknown
+      >
+
+      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<number>()
+
+      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+        undefined | MutateOptions<unknown, DefaultError, number, unknown>
+      >()
+
+      // @ts-expect-error --- required variables
+      mutate()
+      mutate(123, {
+        onError: (e) => {
+          expectTypeOf(e).toEqualTypeOf<DefaultError>()
+        },
+      })
+    })
+
+    describe('compatible with spread arguments pattern', () => {
+      // this is common pattern used internal so we need make sure it still works
+
+      it('void variables', () => {
+        const mutate = {} as (...options: Parameters<MutateFunction>) => void
+
+        expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
+          undefined | void
+        >()
+
+        expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+          undefined | MutateOptions<unknown, DefaultError, void, unknown>
+        >()
+
+        mutate() // can be called with no arguments
+        mutate(undefined, {
+          onError: (e) => {
+            expectTypeOf(e).toEqualTypeOf<DefaultError>()
+          },
+        })
+      })
+
+      it('optional undefinable variables', () => {
+        const mutate = {} as (
+          ...options: Parameters<
+            MutateFunction<unknown, DefaultError, number | undefined, unknown>
+          >
+        ) => void
+
+        expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
+          number | undefined
+        >()
+
+        expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+          | undefined
+          | MutateOptions<unknown, DefaultError, number | undefined, unknown>
+        >()
+
+        mutate() // can be called with no arguments
+        mutate(undefined, {
+          onError: (e) => {
+            expectTypeOf(e).toEqualTypeOf<DefaultError>()
+          },
+        })
+      })
+
+      it('unknown variables', () => {
+        const mutate = {} as (
+          ...options: Parameters<
+            MutateFunction<unknown, DefaultError, unknown, unknown>
+          >
+        ) => void
+
+        expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<unknown>()
+
+        expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+          undefined | MutateOptions<unknown, DefaultError, unknown, unknown>
+        >()
+
+        mutate() // can be called with no arguments
+      })
+
+      it('any variables', () => {
+        const mutate = {} as (
+          ...options: Parameters<
+            MutateFunction<unknown, DefaultError, any, unknown>
+          >
+        ) => void
+
+        expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<any>()
+
+        expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+          undefined | MutateOptions<unknown, DefaultError, any, unknown>
+        >()
+
+        mutate() // can be called with no arguments
+      })
+
+      it('void union variables', () => {
+        const mutate = {} as (
+          ...options: Parameters<
+            MutateFunction<unknown, DefaultError, void | string, unknown>
+          >
+        ) => void
+
+        expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
+          void | string | undefined
+        >()
+
+        expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+          | undefined
+          | MutateOptions<unknown, DefaultError, void | string, unknown>
+        >()
+
+        mutate() // can be called with no arguments
+      })
+
+      it('required non-undefinable variables', () => {
+        const mutate = {} as (
+          ...options: Parameters<
+            MutateFunction<unknown, DefaultError, number, unknown>
+          >
+        ) => void
+
+        expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<number>()
+
+        expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
+          undefined | MutateOptions<unknown, DefaultError, number, unknown>
+        >()
+
+        // @ts-expect-error --- required variables
+        mutate()
+        mutate(123, {
+          onError: (e) => {
+            expectTypeOf(e).toEqualTypeOf<DefaultError>()
+          },
+        })
+      })
+    })
+  })
 })
diff --git a/packages/query-core/src/__tests__/mutations.test.tsx b/packages/query-core/src/__tests__/mutation.test.tsx
similarity index 99%
rename from packages/query-core/src/__tests__/mutations.test.tsx
rename to packages/query-core/src/__tests__/mutation.test.tsx
index 8ad7f644779..6fdd1d5ebd0 100644
--- a/packages/query-core/src/__tests__/mutations.test.tsx
+++ b/packages/query-core/src/__tests__/mutation.test.tsx
@@ -5,7 +5,7 @@ import { MutationObserver } from '../mutationObserver'
 import { executeMutation } from './utils'
 import type { MutationState } from '../mutation'
 
-describe('mutations', () => {
+describe('mutation', () => {
   let queryClient: QueryClient
 
   beforeEach(() => {
diff --git a/packages/query-core/src/__tests__/mutations.test-d.tsx b/packages/query-core/src/__tests__/mutations.test-d.tsx
deleted file mode 100644
index 53465d601cf..00000000000
--- a/packages/query-core/src/__tests__/mutations.test-d.tsx
+++ /dev/null
@@ -1,229 +0,0 @@
-import { describe, expectTypeOf, it } from 'vitest'
-
-import type { DefaultError, MutateFunction, MutateOptions } from '../types'
-
-describe('MutateFunction', () => {
-  it('void variables', () => {
-    const mutate = {} as MutateFunction
-
-    expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
-      undefined | void
-    >()
-
-    expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-      undefined | MutateOptions<unknown, DefaultError, void, unknown>
-    >()
-
-    mutate() // can be called with no arguments
-    mutate(undefined, {
-      onError: (e) => {
-        expectTypeOf(e).toEqualTypeOf<DefaultError>()
-      },
-    })
-  })
-
-  it('optional undefinable variables', () => {
-    const mutate = {} as MutateFunction<
-      unknown,
-      DefaultError,
-      number | undefined,
-      unknown
-    >
-
-    expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
-      number | undefined
-    >()
-
-    expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-      | undefined
-      | MutateOptions<unknown, DefaultError, number | undefined, unknown>
-    >()
-
-    mutate() // can be called with no arguments
-    mutate(undefined, {
-      onError: (e) => {
-        expectTypeOf(e).toEqualTypeOf<DefaultError>()
-      },
-    })
-  })
-
-  it('unknown variables', () => {
-    const mutate = {} as MutateFunction<unknown, DefaultError, unknown, unknown>
-
-    expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<unknown>()
-
-    expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-      undefined | MutateOptions<unknown, DefaultError, unknown, unknown>
-    >()
-
-    mutate() // can be called with no arguments
-  })
-
-  it('any variables', () => {
-    const mutate = {} as MutateFunction<unknown, DefaultError, any, unknown>
-
-    expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<any>()
-
-    expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-      undefined | MutateOptions<unknown, DefaultError, any, unknown>
-    >()
-
-    mutate() // can be called with no arguments
-  })
-
-  it('void union variables', () => {
-    const mutate = {} as MutateFunction<
-      unknown,
-      DefaultError,
-      void | string,
-      unknown
-    >
-
-    expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
-      void | string | undefined
-    >()
-
-    expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-      undefined | MutateOptions<unknown, DefaultError, void | string, unknown>
-    >()
-
-    mutate() // can be called with no arguments
-  })
-
-  it('required non-undefinable variables', () => {
-    const mutate = {} as MutateFunction<unknown, DefaultError, number, unknown>
-
-    expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<number>()
-
-    expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-      undefined | MutateOptions<unknown, DefaultError, number, unknown>
-    >()
-
-    // @ts-expect-error --- required variables
-    mutate()
-    mutate(123, {
-      onError: (e) => {
-        expectTypeOf(e).toEqualTypeOf<DefaultError>()
-      },
-    })
-  })
-
-  describe('compatible with spread arguments pattern', () => {
-    // this is common pattern used internal so we need make sure it still works
-
-    it('void variables', () => {
-      const mutate = {} as (...options: Parameters<MutateFunction>) => void
-
-      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
-        undefined | void
-      >()
-
-      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-        undefined | MutateOptions<unknown, DefaultError, void, unknown>
-      >()
-
-      mutate() // can be called with no arguments
-      mutate(undefined, {
-        onError: (e) => {
-          expectTypeOf(e).toEqualTypeOf<DefaultError>()
-        },
-      })
-    })
-
-    it('optional undefinable variables', () => {
-      const mutate = {} as (
-        ...options: Parameters<
-          MutateFunction<unknown, DefaultError, number | undefined, unknown>
-        >
-      ) => void
-
-      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
-        number | undefined
-      >()
-
-      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-        | undefined
-        | MutateOptions<unknown, DefaultError, number | undefined, unknown>
-      >()
-
-      mutate() // can be called with no arguments
-      mutate(undefined, {
-        onError: (e) => {
-          expectTypeOf(e).toEqualTypeOf<DefaultError>()
-        },
-      })
-    })
-
-    it('unknown variables', () => {
-      const mutate = {} as (
-        ...options: Parameters<
-          MutateFunction<unknown, DefaultError, unknown, unknown>
-        >
-      ) => void
-
-      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<unknown>()
-
-      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-        undefined | MutateOptions<unknown, DefaultError, unknown, unknown>
-      >()
-
-      mutate() // can be called with no arguments
-    })
-
-    it('any variables', () => {
-      const mutate = {} as (
-        ...options: Parameters<
-          MutateFunction<unknown, DefaultError, any, unknown>
-        >
-      ) => void
-
-      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<any>()
-
-      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-        undefined | MutateOptions<unknown, DefaultError, any, unknown>
-      >()
-
-      mutate() // can be called with no arguments
-    })
-
-    it('void union variables', () => {
-      const mutate = {} as (
-        ...options: Parameters<
-          MutateFunction<unknown, DefaultError, void | string, unknown>
-        >
-      ) => void
-
-      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<
-        void | string | undefined
-      >()
-
-      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-        undefined | MutateOptions<unknown, DefaultError, void | string, unknown>
-      >()
-
-      mutate() // can be called with no arguments
-    })
-
-    it('required non-undefinable variables', () => {
-      const mutate = {} as (
-        ...options: Parameters<
-          MutateFunction<unknown, DefaultError, number, unknown>
-        >
-      ) => void
-
-      expectTypeOf<Parameters<typeof mutate>[0]>().toEqualTypeOf<number>()
-
-      expectTypeOf<Parameters<typeof mutate>[1]>().toEqualTypeOf<
-        undefined | MutateOptions<unknown, DefaultError, number, unknown>
-      >()
-
-      // @ts-expect-error --- required variables
-      mutate()
-      mutate(123, {
-        onError: (e) => {
-          expectTypeOf(e).toEqualTypeOf<DefaultError>()
-        },
-      })
-    })
-  })
-})