feat: improve deep equality check failing message for toBe

packages/vitest/src/integrations/chai/jest-expect.ts

@@ -129,9 +129,44 @@ export const JestChaiExpect: ChaiPlugin = (chai, utils) => {
   })
   def('toBe', function (expected) {
     const actual = this._obj
+    const pass = Object.is(actual, expected)
+
+    let toBeMessage = 'expected #{this} to be #{exp} // Object.is equality'
+    if (!pass) {
+      let reminderMessage = 'If it should pass with deep equality, replace "toBe" with "toStrictEqual"\n\n'
+      const toStrictEqualPass = jestEquals(
+        actual,
+        expected,
+        [
+          iterableEquality,
+          typeEquality,
+          sparseArrayEquality,
+          arrayBufferEquality,
+        ],
+        true,
+      )
+
+      if (toStrictEqualPass) {
+        toBeMessage = `${reminderMessage}expected #{this} to be [serializes to the same string] // Object.is equality`
+      }
+      else {
+        const toEqualPass = jestEquals(
+          actual,
+          expected,
+          [iterableEquality],
+        )
+
+        if (toEqualPass) {
+          reminderMessage = 'If it should pass with deep equality, replace "toBe" with "toEqual"\n\n'
+
+          toBeMessage = `${reminderMessage}expected #{this} to be [serializes to the same string] // Object.is equality`
+        }
+      }
+    }
+
     return this.assert(
-      Object.is(actual, expected),
-      'expected #{this} to be #{exp} // Object.is equality',
+      pass,
+      toBeMessage,
       'expected #{this} not to be #{exp} // Object.is equality',
       expected,
       actual,

test/core/test/jest-expect.test.ts

@@ -1,5 +1,6 @@
 /* eslint-disable comma-spacing */
 /* eslint-disable no-sparse-arrays */
+import { AssertionError } from 'assert'
 import { describe, expect, it, vi } from 'vitest'
 
 class TestError extends Error {}
@@ -549,6 +550,52 @@ describe('async expect', () => {
       expect(error).toEqual(expectedError)
     }
   })
+
+  it('reminds users to use deep equality checks if they are comparing objects', () => {
+    const createAssertionError = (
+      deepEqualityName: string,
+      expected: string,
+    ) => new AssertionError({
+      message: 'If it should pass with deep equality, '
+        + `replace "toBe" with "${deepEqualityName}"\n\nexpected ${expected} `
+        + 'to be [serializes to the same string] // Object.is equality',
+    })
+
+    const actual = { key: 'value' }
+    class FakeClass {}
+
+    const toStrictEqualError1 = createAssertionError('toStrictEqual', '{ key: \'value\' }')
+    try {
+      expect(actual).toBe({ ...actual })
+    }
+    catch (error) {
+      expect(error).toEqual(toStrictEqualError1)
+    }
+
+    const toStrictEqualError2 = createAssertionError('toStrictEqual', 'FakeClass{}')
+    try {
+      expect(new FakeClass()).toBe(new FakeClass())
+    }
+    catch (error) {
+      expect(error).toEqual(toStrictEqualError2)
+    }
+
+    const toEqualError1 = createAssertionError('toEqual', '{}')
+    try {
+      expect({}).toBe(new FakeClass())
+    }
+    catch (error) {
+      expect(error).toEqual(toEqualError1)
+    }
+
+    const toEqualError2 = createAssertionError('toEqual', 'FakeClass{}')
+    try {
+      expect(new FakeClass()).toBe({})
+    }
+    catch (error) {
+      expect(error).toEqual(toEqualError2)
+    }
+  })
 })
 
 it('timeout', () => new Promise(resolve => setTimeout(resolve, 500)))