diff --git a/packages/table-core/tests/RowPinning.test.ts b/packages/table-core/tests/RowPinning.test.ts
index 223c37562d..5cd5bcb65a 100644
--- a/packages/table-core/tests/RowPinning.test.ts
+++ b/packages/table-core/tests/RowPinning.test.ts
@@ -1,25 +1,27 @@
-import { describe, expect, it } from 'vitest'
+import { beforeEach, describe, expect, it } from 'vitest'
 import {
-  ColumnDef,
-  createColumnHelper,
   constructTable,
-  createCoreRowModel,
+  coreFeatures,
+  createColumnHelper,
   createPaginatedRowModel,
-  rowPinningFeature,
   rowPaginationFeature,
+  rowPinningFeature,
 } from '../src'
-import { makeData, Person } from './makeTestData'
+import { makeData } from './makeTestData'
+import type { ColumnDef } from '../src'
+import type { Person } from './makeTestData'
 
 type personKeys = keyof Person
-type PersonColumn = ColumnDef<
-  any,
-  Person,
-  string | number | Person[] | undefined
->
+type PersonColumn = ColumnDef<any, Person, any>
 
-function generateColumns(people: Person[]): PersonColumn[] {
+function generateColumns(people: Array<Person>): Array<PersonColumn> {
   const columnHelper = createColumnHelper<any, Person>()
   const person = people[0]
+
+  if (!person) {
+    return []
+  }
+
   return Object.keys(person).map((key) => {
     const typedKey = key as personKeys
     return columnHelper.accessor(typedKey, { id: typedKey })
@@ -27,14 +29,22 @@ function generateColumns(people: Person[]): PersonColumn[] {
 }
 
 describe('rowPinningFeature', () => {
+  let data: Array<Person>
+  let columns: Array<PersonColumn>
+  beforeEach(() => {
+    data = makeData(10)
+    columns = generateColumns(data)
+  })
+
   describe('constructTable', () => {
     describe('getTopRows', () => {
       it('should return pinned rows when keepPinnedRows is true rows are visible', () => {
-        const data = makeData(10)
-        const columns = generateColumns(data)
-
         const table = constructTable<any, Person>({
-          _features: { rowPinningFeature, rowPaginationFeature },
+          _features: {
+            rowPinningFeature,
+            rowPaginationFeature,
+            ...coreFeatures,
+          },
           _rowModels: {
             paginatedRowModel: createPaginatedRowModel(),
           },
@@ -46,7 +56,7 @@ describe('rowPinningFeature', () => {
           state: {
             pagination: {
               pageSize: 5,
-              pageIndex: 0, //pinned rows will be on page 0
+              pageIndex: 0, // pinned rows will be on page 0
             },
             rowPinning: {
               bottom: [],
@@ -59,15 +69,16 @@ describe('rowPinningFeature', () => {
         const result = table.getTopRows()
 
         expect(result.length).toBe(2)
-        expect(result[0].id).toBe('0')
-        expect(result[1].id).toBe('1')
+        expect(result[0]?.id).toBe('0')
+        expect(result[1]?.id).toBe('1')
       })
       it('should return pinned rows when keepPinnedRows is true rows are not visible', () => {
-        const data = makeData(10)
-        const columns = generateColumns(data)
-
         const table = constructTable<any, Person>({
-          _features: { rowPinningFeature, rowPaginationFeature },
+          _features: {
+            rowPinningFeature,
+            rowPaginationFeature,
+            ...coreFeatures,
+          },
           _rowModels: {
             paginatedRowModel: createPaginatedRowModel(),
           },
@@ -79,7 +90,7 @@ describe('rowPinningFeature', () => {
           state: {
             pagination: {
               pageSize: 5,
-              pageIndex: 1, //pinned rows will be on page 0
+              pageIndex: 1, // pinned rows will be on page 0
             },
             rowPinning: {
               bottom: [],
@@ -92,15 +103,16 @@ describe('rowPinningFeature', () => {
         const result = table.getTopRows()
 
         expect(result.length).toBe(2)
-        expect(result[0].id).toBe('0')
-        expect(result[1].id).toBe('1')
+        expect(result[0]?.id).toBe('0')
+        expect(result[1]?.id).toBe('1')
       })
       it('should return pinned rows when keepPinnedRows is false rows are visible', () => {
-        const data = makeData(10)
-        const columns = generateColumns(data)
-
         const table = constructTable<any, Person>({
-          _features: { rowPinningFeature, rowPaginationFeature },
+          _features: {
+            rowPinningFeature,
+            rowPaginationFeature,
+            ...coreFeatures,
+          },
           _rowModels: {
             paginatedRowModel: createPaginatedRowModel(),
           },
@@ -112,7 +124,7 @@ describe('rowPinningFeature', () => {
           state: {
             pagination: {
               pageSize: 5,
-              pageIndex: 0, //pinned rows will be on page 0
+              pageIndex: 0, // pinned rows will be on page 0
             },
             rowPinning: {
               bottom: [],
@@ -125,15 +137,16 @@ describe('rowPinningFeature', () => {
         const result = table.getTopRows()
 
         expect(result.length).toBe(2)
-        expect(result[0].id).toBe('0')
-        expect(result[1].id).toBe('1')
+        expect(result[0]?.id).toBe('0')
+        expect(result[1]?.id).toBe('1')
       })
       it('should not return pinned rows when keepPinnedRows is false and rows are not visible', () => {
-        const data = makeData(10)
-        const columns = generateColumns(data)
-
         const table = constructTable<any, Person>({
-          _features: { rowPinningFeature, rowPaginationFeature },
+          _features: {
+            rowPinningFeature,
+            rowPaginationFeature,
+            ...coreFeatures,
+          },
           _rowModels: {
             paginatedRowModel: createPaginatedRowModel(),
           },
@@ -145,7 +158,7 @@ describe('rowPinningFeature', () => {
           state: {
             pagination: {
               pageSize: 5,
-              pageIndex: 1, //pinned rows will be on page 0, but this is page 1
+              pageIndex: 1, // pinned rows will be on page 0, but this is page 1
             },
             rowPinning: {
               bottom: [],
@@ -161,11 +174,12 @@ describe('rowPinningFeature', () => {
       })
 
       it('should return correct top rows', () => {
-        const data = makeData(10)
-        const columns = generateColumns(data)
-
         const table = constructTable<any, Person>({
-          _features: { rowPinningFeature, rowPaginationFeature },
+          _features: {
+            rowPinningFeature,
+            rowPaginationFeature,
+            ...coreFeatures,
+          },
           _rowModels: {
             paginatedRowModel: createPaginatedRowModel(),
           },
@@ -177,7 +191,7 @@ describe('rowPinningFeature', () => {
           state: {
             pagination: {
               pageSize: 5,
-              pageIndex: 0, //pinned rows will be on page 0
+              pageIndex: 0, // pinned rows will be on page 0
             },
             rowPinning: {
               bottom: [],
@@ -190,15 +204,16 @@ describe('rowPinningFeature', () => {
         const result = table.getTopRows()
 
         expect(result.length).toBe(2)
-        expect(result[0].id).toBe('1')
-        expect(result[1].id).toBe('3')
+        expect(result[0]?.id).toBe('1')
+        expect(result[1]?.id).toBe('3')
       })
       it('should return correct bottom rows', () => {
-        const data = makeData(10)
-        const columns = generateColumns(data)
-
         const table = constructTable<any, Person>({
-          _features: { rowPinningFeature, rowPaginationFeature },
+          _features: {
+            rowPinningFeature,
+            rowPaginationFeature,
+            ...coreFeatures,
+          },
           _rowModels: {
             paginatedRowModel: createPaginatedRowModel(),
           },
@@ -210,7 +225,7 @@ describe('rowPinningFeature', () => {
           state: {
             pagination: {
               pageSize: 5,
-              pageIndex: 0, //pinned rows will be on page 0
+              pageIndex: 0, // pinned rows will be on page 0
             },
             rowPinning: {
               bottom: ['1', '3'],
@@ -223,8 +238,8 @@ describe('rowPinningFeature', () => {
         const result = table.getBottomRows()
 
         expect(result.length).toBe(2)
-        expect(result[0].id).toBe('1')
-        expect(result[1].id).toBe('3')
+        expect(result[0]?.id).toBe('1')
+        expect(result[1]?.id).toBe('3')
       })
     })
     describe('getCenterRows', () => {
@@ -233,7 +248,11 @@ describe('rowPinningFeature', () => {
         const columns = generateColumns(data)
 
         const table = constructTable<any, Person>({
-          _features: { rowPinningFeature, rowPaginationFeature },
+          _features: {
+            rowPinningFeature,
+            rowPaginationFeature,
+            ...coreFeatures,
+          },
           _rowModels: {
             paginatedRowModel: createPaginatedRowModel(),
           },
@@ -258,8 +277,8 @@ describe('rowPinningFeature', () => {
         const result = table.getCenterRows()
 
         expect(result.length).toBe(2)
-        expect(result[0].id).toBe('0') // 0 and 5 are the only rows not pinned
-        expect(result[1].id).toBe('5')
+        expect(result[0]?.id).toBe('0') // 0 and 5 are the only rows not pinned
+        expect(result[1]?.id).toBe('5')
       })
     })
   })
diff --git a/packages/table-core/tests/RowSelection.test.ts b/packages/table-core/tests/RowSelection.test.ts
index 439e693361..e6213d5f7b 100644
--- a/packages/table-core/tests/RowSelection.test.ts
+++ b/packages/table-core/tests/RowSelection.test.ts
@@ -1,24 +1,26 @@
 import { describe, expect, it } from 'vitest'
 import {
-  ColumnDef,
-  createColumnHelper,
   constructTable,
-  createCoreRowModel,
+  coreFeatures,
+  createColumnHelper,
   rowSelectionFeature,
 } from '../src'
 import * as RowSelectionUtils from '../src/features/row-selection/rowSelectionFeature.utils'
-import { makeData, Person } from './makeTestData'
+import { makeData } from './makeTestData'
+import type { Person } from './makeTestData'
+import type { ColumnDef } from '../src'
 
 type personKeys = keyof Person
-type PersonColumn = ColumnDef<
-  any,
-  Person,
-  string | number | Person[] | undefined
->
+type PersonColumn = ColumnDef<any, Person, any>
 
-function generateColumns(people: Person[]): PersonColumn[] {
+function generateColumns(people: Array<Person>): Array<PersonColumn> {
   const columnHelper = createColumnHelper<any, Person>()
   const person = people[0]
+
+  if (!person) {
+    return []
+  }
+
   return Object.keys(person).map((key) => {
     const typedKey = key as personKeys
     return columnHelper.accessor(typedKey, { id: typedKey })
@@ -32,7 +34,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: true,
         onStateChange() {},
@@ -49,7 +51,7 @@ describe('rowSelectionFeature', () => {
       })
       const rowModel = table.getCoreRowModel()
 
-      const result = RowSelectionUtils.selectRowsFn(table, rowModel)
+      const result = RowSelectionUtils.selectRowsFn(rowModel)
 
       expect(result.rows.length).toBe(2)
       expect(result.flatRows.length).toBe(2)
@@ -62,7 +64,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: true,
         onStateChange() {},
@@ -79,9 +81,9 @@ describe('rowSelectionFeature', () => {
       })
       const rowModel = table.getCoreRowModel()
 
-      const result = RowSelectionUtils.selectRowsFn(table, rowModel)
+      const result = RowSelectionUtils.selectRowsFn(rowModel)
 
-      expect(result.rows[0].subRows.length).toBe(1)
+      expect(result.rows[0]?.subRows?.length).toBe(1)
       expect(result.flatRows.length).toBe(2)
       expect(result.rowsById).toHaveProperty('0')
       expect(result.rowsById).toHaveProperty('0.0')
@@ -92,7 +94,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: true,
         onStateChange() {},
@@ -106,7 +108,7 @@ describe('rowSelectionFeature', () => {
       })
       const rowModel = table.getCoreRowModel()
 
-      const result = RowSelectionUtils.selectRowsFn(table, rowModel)
+      const result = RowSelectionUtils.selectRowsFn(rowModel)
 
       expect(result.rows.length).toBe(0)
       expect(result.flatRows.length).toBe(0)
@@ -115,43 +117,101 @@ describe('rowSelectionFeature', () => {
   })
   describe('isRowSelected', () => {
     it('should return true if the row id exists in selection and is set to true', () => {
-      const row = { id: '123', data: {} } as any
-      const selection: Record<string, boolean> = {
-        '123': true,
-        '456': false,
-      }
+      const data = makeData(3)
+      const columns = generateColumns(data)
 
-      const result = RowSelectionUtils.isRowSelected(row, selection)
+      const table = constructTable<any, Person>({
+        _features: { rowSelectionFeature, ...coreFeatures },
+        _rowModels: {},
+        enableRowSelection: true,
+        onStateChange() {},
+        renderFallbackValue: '',
+        data,
+        state: {
+          rowSelection: {
+            '123': true,
+            '456': false,
+          },
+        },
+        columns,
+      })
+
+      const row = { id: '123', data: {}, table } as any
+
+      const result = RowSelectionUtils.isRowSelected(row)
       expect(result).toEqual(true)
     })
 
     it('should return false if the row id exists in selection and is set to false', () => {
-      const row = { id: '456', data: {} } as any
-      const selection: Record<string, boolean> = {
-        '123': true,
-        '456': false,
-      }
+      const data = makeData(3)
+      const columns = generateColumns(data)
 
-      const result = RowSelectionUtils.isRowSelected(row, selection)
+      const table = constructTable<any, Person>({
+        _features: { rowSelectionFeature, ...coreFeatures },
+        _rowModels: {},
+        enableRowSelection: true,
+        onStateChange() {},
+        renderFallbackValue: '',
+        data,
+        state: {
+          rowSelection: {
+            '123': true,
+            '456': false,
+          },
+        },
+        columns,
+      })
+
+      const row = { id: '456', data: {}, table } as any
+
+      const result = RowSelectionUtils.isRowSelected(row)
       expect(result).toEqual(false)
     })
 
     it('should return false if the row id does not exist in selection', () => {
-      const row = { id: '789', data: {} } as any
-      const selection: Record<string, boolean> = {
-        '123': true,
-        '456': false,
-      }
+      const data = makeData(3)
+      const columns = generateColumns(data)
+
+      const table = constructTable<any, Person>({
+        _features: { rowSelectionFeature, ...coreFeatures },
+        _rowModels: {},
+        enableRowSelection: true,
+        onStateChange() {},
+        renderFallbackValue: '',
+        data,
+        state: {
+          rowSelection: {
+            '123': true,
+            '456': false,
+          },
+        },
+        columns,
+      })
 
-      const result = RowSelectionUtils.isRowSelected(row, selection)
+      const row = { id: '789', data: {}, table } as any
+
+      const result = RowSelectionUtils.isRowSelected(row)
       expect(result).toEqual(false)
     })
 
     it('should return false if selection is an empty object', () => {
-      const row = { id: '789', data: {} } as any
-      const selection: Record<string, boolean> = {}
+      const data = makeData(3)
+      const columns = generateColumns(data)
+
+      const table = constructTable<any, Person>({
+        _features: { rowSelectionFeature, ...coreFeatures },
+        _rowModels: {},
+        enableRowSelection: true,
+        onStateChange() {},
+        renderFallbackValue: '',
+        data,
+        state: {},
+        columns,
+      })
+
+      const row = { id: '789', data: {}, table } as any
 
-      const result = RowSelectionUtils.isRowSelected(row, selection)
+      const result = RowSelectionUtils.isRowSelected(row)
       expect(result).toEqual(false)
     })
   })
@@ -161,7 +221,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: true,
         onStateChange() {},
@@ -171,13 +231,9 @@ describe('rowSelectionFeature', () => {
         columns,
       })
 
-      const firstRow = table.getCoreRowModel().rows[0]
+      const firstRow = table.getCoreRowModel().rows[0]!
 
-      const result = RowSelectionUtils.isSubRowSelected(
-        firstRow,
-        table.getState().rowSelection,
-        table,
-      )
+      const result = RowSelectionUtils.isSubRowSelected(firstRow)
 
       expect(result).toEqual(false)
     })
@@ -187,7 +243,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: true,
         onStateChange() {},
@@ -200,13 +256,9 @@ describe('rowSelectionFeature', () => {
         columns,
       })
 
-      const firstRow = table.getCoreRowModel().rows[0]
+      const firstRow = table.getCoreRowModel().rows[0]!
 
-      const result = RowSelectionUtils.isSubRowSelected(
-        firstRow,
-        table.getState().rowSelection,
-        table,
-      )
+      const result = RowSelectionUtils.isSubRowSelected(firstRow)
 
       expect(result).toEqual(false)
     })
@@ -216,7 +268,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: true,
         onStateChange() {},
@@ -231,13 +283,9 @@ describe('rowSelectionFeature', () => {
         columns,
       })
 
-      const firstRow = table.getCoreRowModel().rows[0]
+      const firstRow = table.getCoreRowModel().rows[0]!
 
-      const result = RowSelectionUtils.isSubRowSelected(
-        firstRow,
-        table.getState().rowSelection,
-        table,
-      )
+      const result = RowSelectionUtils.isSubRowSelected(firstRow)
 
       expect(result).toEqual('some')
     })
@@ -247,7 +295,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: true,
         onStateChange() {},
@@ -263,13 +311,9 @@ describe('rowSelectionFeature', () => {
         columns,
       })
 
-      const firstRow = table.getCoreRowModel().rows[0]
+      const firstRow = table.getCoreRowModel().rows[0]!
 
-      const result = RowSelectionUtils.isSubRowSelected(
-        firstRow,
-        table.getState().rowSelection,
-        table,
-      )
+      const result = RowSelectionUtils.isSubRowSelected(firstRow)
 
       expect(result).toEqual('all')
     })
@@ -278,7 +322,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: (row) => row.index === 0, // only first row is selectable (of 2 sub-rows)
         onStateChange() {},
@@ -293,13 +337,9 @@ describe('rowSelectionFeature', () => {
         columns,
       })
 
-      const firstRow = table.getCoreRowModel().rows[0]
+      const firstRow = table.getCoreRowModel().rows[0]!
 
-      const result = RowSelectionUtils.isSubRowSelected(
-        firstRow,
-        table.getState().rowSelection,
-        table,
-      )
+      const result = RowSelectionUtils.isSubRowSelected(firstRow)
 
       expect(result).toEqual('all')
     })
@@ -308,7 +348,7 @@ describe('rowSelectionFeature', () => {
       const columns = generateColumns(data)
 
       const table = constructTable<any, Person>({
-        _features: { rowSelectionFeature },
+        _features: { rowSelectionFeature, ...coreFeatures },
         _rowModels: {},
         enableRowSelection: true,
         onStateChange() {},
@@ -323,13 +363,9 @@ describe('rowSelectionFeature', () => {
         columns,
       })
 
-      const firstRow = table.getCoreRowModel().rows[0]
+      const firstRow = table.getCoreRowModel().rows[0]!
 
-      const result = RowSelectionUtils.isSubRowSelected(
-        firstRow,
-        table.getState().rowSelection,
-        table,
-      )
+      const result = RowSelectionUtils.isSubRowSelected(firstRow)
 
       expect(result).toEqual('some')
     })
diff --git a/packages/table-core/tests/getGroupedRowModel.test.ts b/packages/table-core/tests/getGroupedRowModel.test.ts
index 92bce5186f..0447113fdb 100644
--- a/packages/table-core/tests/getGroupedRowModel.test.ts
+++ b/packages/table-core/tests/getGroupedRowModel.test.ts
@@ -1,24 +1,27 @@
 import { describe, expect, it } from 'vitest'
 import {
+  aggregationFns,
+  columnGroupingFeature,
   constructTable,
-  ColumnDef,
-  createCoreRowModel,
+  coreFeatures,
   createGroupedRowModel,
-  columnGroupingFeature,
 } from '../src'
 import { createColumnHelper } from '../src/helpers/columnHelper'
-import { makeData, Person } from './makeTestData'
+import { makeData } from './makeTestData'
+import type { Person } from './makeTestData'
+import type { ColumnDef } from '../src'
 
 type personKeys = keyof Person
-type PersonColumn = ColumnDef<
-  any,
-  Person,
-  string | number | Person[] | undefined
->
+type PersonColumn = ColumnDef<any, Person, any>
 
-function generateColumns(people: Person[]): PersonColumn[] {
+function generateColumns(people: Array<Person>): Array<PersonColumn> {
   const columnHelper = createColumnHelper<any, Person>()
   const person = people[0]
+
+  if (!person) {
+    return []
+  }
+
   return Object.keys(person).map((key) => {
     const typedKey = key as personKeys
     return columnHelper.accessor(typedKey, { id: typedKey })
@@ -37,9 +40,9 @@ describe('#getGroupedRowModel', () => {
     data.forEach((p) => (p.age = 123))
 
     const table = constructTable<any, Person>({
-      _features: { columnGroupingFeature },
+      _features: { columnGroupingFeature, ...coreFeatures },
       _rowModels: {
-        groupedRowModel: createGroupedRowModel(),
+        groupedRowModel: createGroupedRowModel(aggregationFns),
       },
       onStateChange() {},
       renderFallbackValue: '',
@@ -50,12 +53,13 @@ describe('#getGroupedRowModel', () => {
     const groupedById = table.getGroupedRowModel().rowsById
     const end = new Date()
 
-    expect(groupedById['firstName:Fixed'].leafRows.length).toEqual(50000)
+    expect(groupedById['firstName:Fixed']?.getLeafRows().length).toEqual(50002)
     expect(
-      groupedById['firstName:Fixed>lastName:Name'].leafRows.length,
-    ).toEqual(50000)
+      groupedById['firstName:Fixed>lastName:Name']?.getLeafRows().length,
+    ).toEqual(50001)
     expect(
-      groupedById['firstName:Fixed>lastName:Name>age:123'].leafRows.length,
+      groupedById['firstName:Fixed>lastName:Name>age:123']?.getLeafRows()
+        .length,
     ).toEqual(50000)
     expect(end.valueOf() - start.valueOf()).toBeLessThan(5000)
   })
diff --git a/packages/table-core/tsconfig.json b/packages/table-core/tsconfig.json
index eb63835950..44533f71cd 100644
--- a/packages/table-core/tsconfig.json
+++ b/packages/table-core/tsconfig.json
@@ -1,4 +1,4 @@
 {
   "extends": "../../tsconfig.json",
-  "include": ["src", "eslint.config.js", "vite.config.ts"]
+  "include": ["src", "eslint.config.js", "vite.config.ts", "tests"]
 }