[Test Migration] Pt 2 - move `packages/core` from Karma to Vitest by cameronjoyner · Pull Request #7709 · palantir/blueprint

cameronjoyner · 2026-01-14T18:56:48Z

Background

Why Vitest instead of Karma?
Karma is a tool that allows you to execute JavaScript code in multiple real browsers. It was deprecated in April of 2023 and they even recommend moving to Jest or Vitest. Online you can find folks who maintain similar products pondering which to switch to [example 1, example 2]

Vitest’s documentation claims that their product can live in harmony with Jest, however it would be duplicative. They claim:

Vitest is an interesting option as it gives you a faster run for your unit tests and a jump in DX thanks to the default watch mode using Vite instant Hot Module Reload (HMR). Vitest offers compatibility with most of the Jest API and ecosystem libraries, so in most projects, it should be a drop-in replacement for Jest.

Moving away from Karma also aligns with the precedent set in packages/labs

Why not Jest?
Vitest intentionally mirrors Jest's API (describe, it, expect, mocking, etc), runs faster, and includes a built-in UI for browsing test results, better inline snapshots, and native support for features like concurrent test execution

Why move off of Chai?
Mocha is a test framework running on Node.js and in the browser. Mocha is a popular choice for server-side testing. Mocha is highly configurable and does not include certain features by default. For example, it does not come with an assertion library, which is why we use the popular Mocha assertions complement, Chai.

We originally introduced it in #1741, 8 years ago. I don’t see its usage/existence as a bad thing, but by moving off of Chai we may be able to naturally move off of Mocha.

Differences between Labs and Core

	packages/core (Old)	packages/labs (New)
Test Runner	Karma + Mocha	Vitest
File Naming	`*Tests.tsx`	`*.test.tsx`
File Location	Separate test/ dir	Colocated with source
Assertions	Chai (.to.be.true)	Vitest (.toBe(true))
Mocking	Sinon (spy, stub)	Vitest (vi.fn(), vi.spyOn())
Test Discovery	Manual imports in test/index.ts	Glob pattern auto-discovery
DOM Environment	Real browser via Karma	jsdom

FLUPs to this PR
Move tests to adhere to colocation standards in /labs then migrate other packages to vitest, rinse, repeat

Changes proposed in this pull request:

Migrate packages/core from Karma to Vitest

Must give due credit to Greg's initial exploration in gdouglas/vitest-experiment

changelog-app · 2026-01-14T18:56:55Z

svc-palantir-github · 2026-01-14T21:03:57Z

ran pnpm format on overlay2Tests

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svc-palantir-github · 2026-01-15T15:23:30Z

noEmit and skipLibCheck

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svc-palantir-github · 2026-01-15T21:30:35Z

further simplications

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packages/core/karma.conf.js

packages/core/package.json

packages/core/src/components/tooltip/tooltip.md

packages/core/test/alert/alertTests.tsx

ggdouglas · 2026-01-20T19:41:01Z

packages/core/test/resize-sensor/resizeSensorTests.tsx

 import { sleep } from "../utils";

-describe("<ResizeSensor>", () => {
+describe.skip("<ResizeSensor>", () => {


Do we have a plan for how we should implement these sorts of tests that are more reliant on web APIs?

svc-palantir-github · 2026-01-21T15:20:33Z

centralize dependencies in one location

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svc-palantir-github · 2026-01-21T15:43:48Z

central naming

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cameronjoyner · 2026-01-21T15:50:48Z

packages/test-commons/vitestConfig.mts

+export function createBlueprintVitestConfig(options: BlueprintVitestOptions = {}) {
+    const { include = ["test/**/*Tests.{ts,tsx}"], exclude = [], includeEnzyme = true } = options;
+
+    const setupFile = includeEnzyme
+        ? "@blueprintjs/test-commons/vitest.setup"
+        : "@blueprintjs/test-commons/vitest-setup-no-enzyme";
+
+    return defineConfig({
+        plugins: [react()],
+        test: {
+            environment: "jsdom",
+            exclude: ["lib/**", "node_modules/**", ...exclude],
+            include,
+            setupFiles: setupFile,
+        },
+    });
+}


svc-palantir-github · 2026-01-21T19:35:37Z

fixing lint

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svc-palantir-github · 2026-01-21T19:49:12Z

prettier

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svc-palantir-github · 2026-01-21T23:29:01Z

linter error + vitest coverage

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svc-palantir-github · 2026-01-22T22:42:04Z

Compressing to one commit

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svc-palantir-github · 2026-01-22T22:57:12Z

pnpm install

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…undle

svc-palantir-github · 2026-02-02T17:04:25Z

fix lint

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packages/core/test/buttons/buttonTests.tsx

ggdouglas · 2026-02-02T19:32:42Z

packages/core/test/hotkeys/hotkeyTests.tsx

    it("renders hotkey label", () => {
        render(<Hotkey combo="cmd+C" label="test copy me" group="editing" />);
-        expect(screen.getByText("test copy me")).not.to.be.undefined;
+        expect(screen.getByText("test copy me")).to.not.be.undefined;


nit: Similar to above, I think this would be better described by:

Suggested change

expect(screen.getByText("test copy me")).to.not.be.undefined;

expect(screen.getByText("test copy me")).toBeInTheDocument();

see: https://testing-library.com/docs/guide-disappearance

packages/core/test/index.ts

packages/datetime/test/components/timePickerTests.tsx

packages/core/package.json

ggdouglas · 2026-02-02T19:54:14Z

packages/core/test/tsconfig.json

        "lib": ["dom", "dom.iterable", "es5", "es2015.collection", "es2015.iterable", "es2015.promise"],
-        "noEmit": true
+        "noEmit": true,
+        "skipLibCheck": true


Similar to the last PR, is there anything necessitating these changes to the tsconfig.json files? Is this needed?

Ok I added this back and want to reopen the discussion. I did this today to skip type-checking for .d.ts files.

I believe this has to do with moduleResolution.

In /core/src/design-tokens/tsconfig.json: "moduleResolution": "Bundler",

In /config/tsconfig.web.json: "moduleResolution": "node",

In /config/tsconfig.node.json: "moduleResolution": "node16",

packages/core/test/tsconfig.json
└── extends: ../src/tsconfig.json
└── extends: config/tsconfig.web.json

Still investigating. It seems that use of bundler is partially to blame for this.

packages/node-build-scripts/src/cssVariables.mjs

packages/table/test/formats/jsonFormatTests.tsx

ggdouglas · 2026-02-02T20:08:37Z

packages/core/package.json

-        "enzyme": "^3.11.0",
-        "karma": "^6.4.2",
+        "@vitejs/plugin-react": "catalog:",
+        "@vitest/coverage-v8": "catalog:",


Where is the @vitest/coverage-v8 dep used? Should it be included in the test-commons deps?

svc-palantir-github · 2026-02-02T20:42:30Z

responding to usage of toBeInTheDocument

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svc-palantir-github · 2026-02-02T23:07:39Z

dedupe

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package.json

packages/core/test/overflow-list/overflowListTests.tsx

svc-palantir-github · 2026-02-03T16:56:13Z

addressing usage of after() and before()

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cameronjoyner · 2026-02-03T17:02:13Z

packages/test-commons/vitest.d.ts

+ * Licensed under the Apache License, Version 2.0 (the "License");
+ */
+
+/// <reference types="@testing-library/jest-dom/vitest" />


@ggdouglas I haven't worked a ton with *.d.ts files and am wondering if this file is unnecessarily exporting export { test, it, beforeAll, afterAll, describe, beforeEach, afterEach, expect, assert, vi } from "vitest";

I don't think that I can use /// <reference types="@testing-library/jest-dom/vitest" /> in a normal .ts file

svc-palantir-github · 2026-02-03T17:05:25Z

removing a dep from package.json

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svc-palantir-github · 2026-02-03T17:28:41Z

removing unused dep from /core

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svc-palantir-github · 2026-02-04T13:55:43Z

skip type-checking of declaration files (.d.ts)

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cameronjoyner added Do not review do not merge labels Jan 14, 2026

cameronjoyner removed the Do not review label Jan 15, 2026

cameronjoyner requested a review from ggdouglas January 16, 2026 02:27

cameronjoyner mentioned this pull request Jan 16, 2026

[Test Migration] Pt 3 - colocate packages/core tests with their components #7714

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cameronjoyner removed the do not merge label Jan 20, 2026

cameronjoyner marked this pull request as ready for review January 20, 2026 16:48

cameronjoyner changed the title ~~[DRAFT] Migrate packages/core from Karma to Vitest~~ Migrate packages/core from Karma to Vitest Jan 20, 2026

ggdouglas reviewed Jan 20, 2026

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cameronjoyner changed the title ~~Migrate packages/core from Karma to Vitest~~ [Test Migration] Pt 2 - move packages/core from Karma to Vitest Jan 22, 2026

cameronjoyner force-pushed the cj/vitest-core branch from 0c9c0a3 to f193ff3 Compare January 22, 2026 22:31

skipLibCheck

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Cameron Joyner added 2 commits January 22, 2026 17:45

merge conflicts resolved

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pnpm install

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cameronjoyner force-pushed the cj/vitest-core branch from f193ff3 to 31b9646 Compare January 22, 2026 22:46

cameronjoyner changed the base branch from develop to cj/package-json-alignment January 22, 2026 22:46

Cameron Joyner added 2 commits January 23, 2026 09:45

remove export of vitest from index s.t. we dont confuse the webpack b…

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…undle

pnpm format

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responding to usage of toBeInTheDocument

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Cameron Joyner added 4 commits February 2, 2026 17:27

removing changes to anything but core

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adding some things back

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reverting usage of dispatchMouseEvent

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dedupe

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Cameron Joyner added 2 commits February 3, 2026 11:32

addressing usage of after() and before()

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removing a dep from package.json

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copyright

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cameronjoyner requested a review from ggdouglas February 3, 2026 17:02

removing unused dep from /core

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skip type-checking of declaration files (.d.ts)

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	expect(screen.getByText("test copy me")).to.not.be.undefined;
	expect(screen.getByText("test copy me")).toBeInTheDocument();

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Background

Changes proposed in this pull request:

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Generate changelog in packages/core/changelog/@unreleased

Generate changelog in packages/test-commons/changelog/@unreleased

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svc-palantir-github commented Jan 14, 2026

ran pnpm format on overlay2Tests

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noEmit and skipLibCheck

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svc-palantir-github commented Jan 15, 2026

further simplications

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svc-palantir-github commented Jan 21, 2026

centralize dependencies in one location

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central naming

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svc-palantir-github commented Jan 21, 2026

fixing lint

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prettier

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linter error + vitest coverage

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Compressing to one commit

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pnpm install

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fix lint

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svc-palantir-github commented Feb 2, 2026

responding to usage of toBeInTheDocument

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dedupe

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