expect(result).toEqual(expect.objectContaining(...)) broken in V4 when result is a Proxy. #9488
Description
Describe the bug
Here is a regular test testing against a proxy:
// V3 ✅
// V4 ✅
it("v1", () => {
const target = {
page: 2,
pageSize: 30,
foo: "bar",
};
const handler = {
get(target, prop) {
return target[prop];
},
};
const proxy = new Proxy(target, handler);
expect(proxy).toEqual(
expect.objectContaining({
page: 2,
foo: "bar",
}),
);
});This passes in both V3 and V4.
If we change our handler implementation to:
const handler = {
get(target, prop) {
return "world";
},
};ie. all fields will return 'world' no matter what, then we get apparently broken behaviour.
V4 erroneously passes the test. It appears to ignore the proxy implementation.
// This test should be failing.
// V3 ❌ (correct)
// V4 ✅ (incorrect)
it("v2", () => {
const target = {
page: 2,
pageSize: 30,
foo: "bar",
};
const handler = {
get(target, prop) {
return "world";
},
};
const proxy = new Proxy(target, handler);
expect(proxy).toEqual(
expect.objectContaining({
page: 2,
foo: "bar",
}),
);
});V4 erroneously fails the test
// This test should be passing.
// V3 ✅ (correct)
// V4 ❌ (incorrect)
it("v2 - inverse", () => {
const target = {
page: 2,
pageSize: 30,
foo: "bar",
};
const handler = {
get(target, prop) {
return "world";
},
};
const proxy = new Proxy(target, handler);
expect(proxy).toEqual(
expect.objectContaining({
page: "world",
foo: "world",
}),
);
}); FAIL src/objectContaining.test.ts > proxy > v2 - inverse
AssertionError: expected { page: 'world', …(2) } to deeply equal ObjectContaining{…}
- Expected
+ Received
- ObjectContaining {
+ {
"foo": "world",
"page": "world",
+ "pageSize": "world",
}
❯ src/objectContaining.test.ts:116:19
114|
115| const proxy = new Proxy(target, handler);
116| expect(proxy).toEqual(
| ^
117| expect.objectContaining({
118| page: "world",
It seems to be tripping up on the extra property pageSize that is not in the objectContaining.
Note that it doesn't have a problem with the values of foo and page.
V4 erroneously fails the test 2
// This test should be passing.
// V3 ✅ (correct)
// V4 ❌ (incorrect)
it("v2 - inverse 2", () => {
const target = {
page: 2,
pageSize: 30,
foo: "bar",
};
const handler = {
get(target, prop) {
return "world";
},
};
const proxy = new Proxy(target, handler);
expect(proxy).toEqual(
expect.objectContaining({
page: "world",
foo: "world",
pageSize: "world",
}),
);
});
}); FAIL src/objectContaining.test.ts > proxy > v2 - inverse 2
AssertionError: expected { page: 'world', …(2) } to deeply equal ObjectContaining{…}
- Expected
+ Received
- ObjectContaining {
+ {
"foo": "world",
"page": "world",
"pageSize": "world",
}
❯ src/objectContaining.test.ts:141:19
139|
140| const proxy = new Proxy(target, handler);
141| expect(proxy).toEqual(
| ^
142| expect.objectContaining({
143| page: "world",
This further demonstrates that it's not the values that it is apparently tripping up on - but there is some equality checking fail here.
Reproduction
https://github.com/dwjohnston/vitest-broken-proxies
Other notes:
I initially discovered this migrating a vue project from vitest 3 to 4.
A vue test like this:
it("v2", () => {
const p2 = reactive({
page: computed(() => 2),
pageSize: computed(() => 30),
foo: computed(() => "bar"),
});
expect(p2).toEqual(
expect.objectContaining({
page: 2,
foo: "bar",
}),
);
});Will fail in the same manner.
System Info
System:
OS: macOS 15.6.1
CPU: (12) arm64 Apple M4 Pro
Memory: 97.77 MB / 24.00 GB
Shell: 5.9 - /bin/zsh
Binaries:
Node: 22.21.1 - /Users/davidjohnston/.nvm/versions/node/v22.21.1/bin/node
npm: 11.6.2 - /Users/davidjohnston/.nvm/versions/node/v22.21.1/bin/npm
pnpm: 10.16.1 - /Users/davidjohnston/Library/pnpm/pnpm
bun: 1.2.21 - /Users/davidjohnston/.bun/bin/bun
Browsers:
Brave Browser: 143.1.85.120
Chrome: 144.0.7559.59
Edge: 144.0.3719.82
Firefox: 147.0.1
Safari: 18.6
npmPackages:
vitest: 4.0.17 => 4.0.17Used Package Manager
npm
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