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Skillssolid-impl-testing

solid-impl-testing

Testing & quality

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Updated 10-16 08:50

About this skill

solid-impl-testing

Quick Reference

Installation

npm install --save-dev @solidjs/testing-library @testing-library/jest-dom vitest
npm install --save-dev vite-plugin-solid

Key Dependencies

Package Role
@solidjs/testing-library SolidJS-specific render, cleanup, renderHook, testEffect
@testing-library/dom Re-exported: screen, fireEvent, waitFor, within, queries
@testing-library/jest-dom DOM matchers (toBeInTheDocument, toHaveTextContent)
vitest Test runner (recommended over Jest for SolidJS)
vite-plugin-solid Compiles JSX/TSX for tests (v2.8.2+ handles test config automatically)

Vitest Configuration

// vite.config.ts
import { defineConfig } from "vitest/config";
import solidPlugin from "vite-plugin-solid";

export default defineConfig({
  plugins: [solidPlugin()],
  resolve: {
    conditions: ["development", "browser"],
  },
  test: {
    environment: "jsdom",
    globals: true,
    setupFiles: ["./src/test-setup.ts"],
    deps: {
      optimizer: {
        web: {
          include: ["solid-js", "@solidjs/router"],
        },
      },
    },
  },
});

// src/test-setup.ts
import "@testing-library/jest-dom";

Critical Warnings

ALWAYS pass a function returning JSX to render() -- NEVER pass JSX directly. SolidJS render() requires () => <Component />, not <Component />. Passing JSX directly executes it outside the test's reactive owner and breaks cleanup.

ALWAYS call cleanup() in afterEach -- even though the library claims auto-cleanup, explicitly calling it prevents disposal errors across test suites. Omitting cleanup causes reactive owners to leak between tests.

NEVER use rerender() -- it does NOT exist in solid-testing-library. SolidJS does not re-render; it executes side effects from reactive state changes. Use signals to drive state changes in tests instead.

NEVER destructure props in test components -- this breaks reactivity tracking. Use props.value access patterns, same as production components.

ALWAYS set resolve.conditions: ["development", "browser"] in Vitest config -- without this, Solid loads the server bundle in tests, causing hydration errors and missing DOM APIs.

Decision Trees

Which Testing API to Use

Need to test a component?
├─ Yes → render(() => <Component />) + screen queries
│   ├─ Component uses router? → Add { location: "/path" } option
│   ├─ Component uses context? → Add { wrapper: Provider } option
│   └─ Component has async data? → Use findBy* queries + waitFor
│
├─ Need to test a custom hook?
│   └─ Yes → renderHook(useMyHook) → access result directly
│
├─ Need to test a custom directive?
│   └─ Yes → renderDirective(myDirective) → use setArg for updates
│
└─ Need to test reactive effects?
    └─ Yes → testEffect(done => createEffect(() => { ... done() }))

Which Query to Use

Can the element be found by its accessible role?
├─ Yes → getByRole("button", { name: "Submit" })       ← PREFERRED
│
├─ Is it a form field with a label?
│   └─ Yes → getByLabelText("Email")
│
├─ Does it have visible text content?
│   └─ Yes → getByText("Hello World")
│
├─ Is the element absent and you want to assert that?
│   └─ Yes → queryByText("Missing") → expect to be null
│
├─ Does the element appear asynchronously?
│   └─ Yes → findByText("Loaded Data")                 ← returns Promise
│
└─ No semantic way to find it?
    └─ Use getByTestId("my-element")                    ← LAST RESORT

Core Patterns

Pattern 1: Basic Component Test

// Counter.test.tsx
import { render, screen, cleanup } from "@solidjs/testing-library";
import { fireEvent } from "@testing-library/dom";
import { afterEach, describe, expect, it } from "vitest";
import { Counter } from "./Counter";

afterEach(() => cleanup());

describe("Counter", () => {
  it("increments on click", async () => {
    render(() => <Counter />);

    const button = screen.getByRole("button", { name: "Increment" });
    expect(screen.getByText("Count: 0")).toBeInTheDocument();

    fireEvent.click(button);
    expect(screen.getByText("Count: 1")).toBeInTheDocument();
  });
});

Pattern 2: Testing with Props via Signals

import { createSignal } from "solid-js";
import { render, screen, cleanup } from "@solidjs/testing-library";
import { afterEach, expect, it } from "vitest";
import { Greeting } from "./Greeting";

afterEach(() => cleanup());

it("reacts to prop changes", () => {
  const [name, setName] = createSignal("Alice");

  // Pass signal getter as prop -- component updates reactively
  render(() => <Greeting name={name()} />);

  expect(screen.getByText("Hello, Alice")).toBeInTheDocument();

  setName("Bob");
  expect(screen.getByText("Hello, Bob")).toBeInTheDocument();
});

Pattern 3: Testing with Context Providers

import { render, screen, cleanup } from "@solidjs/testing-library";
import { afterEach, expect, it } from "vitest";
import { ThemeProvider } from "./ThemeContext";
import { ThemedButton } from "./ThemedButton";

afterEach(() => cleanup());

it("uses theme from context", () => {
  render(() => <ThemedButton />, {
    wrapper: (props) => (
      <ThemeProvider theme="dark">{props.children}</ThemeProvider>
    ),
  });

  expect(screen.getByRole("button")).toHaveClass("dark-theme");
});

Pattern 4: Testing Async Components

import { render, screen, cleanup } from "@solidjs/testing-library";
import { waitFor } from "@testing-library/dom";
import { afterEach, expect, it } from "vitest";
import { UserProfile } from "./UserProfile";

afterEach(() => cleanup());

it("loads and displays user data", async () => {
  render(() => <UserProfile userId="123" />);

  // Suspense fallback shows first
  expect(screen.getByText("Loading...")).toBeInTheDocument();

  // Wait for async data to resolve
  await waitFor(() => {
    expect(screen.getByText("John Doe")).toBeInTheDocument();
  });
});

Pattern 5: Testing Custom Hooks

import { renderHook, cleanup } from "@solidjs/testing-library";
import { afterEach, expect, it } from "vitest";
import { useCounter } from "./useCounter";

afterEach(() => cleanup());

it("returns count and increment", () => {
  const { result } = renderHook(() => useCounter());

  expect(result.count()).toBe(0);
  result.increment();
  expect(result.count()).toBe(1);
});

Pattern 6: Testing with Router

import { render, screen, cleanup } from "@solidjs/testing-library";
import { afterEach, expect, it } from "vitest";
import { App } from "./App";

afterEach(() => cleanup());

it("renders the correct route", async () => {
  render(() => <App />, { location: "/users/42" });

  // Router setup is async -- use findBy queries
  const heading = await screen.findByText("User 42");
  expect(heading).toBeInTheDocument();
});

Pattern 7: Testing Reactive Effects with testEffect

import { createSignal, createEffect } from "solid-js";
import { testEffect, cleanup } from "@solidjs/testing-library";
import { afterEach, expect, it } from "vitest";

afterEach(() => cleanup());

it("tracks signal changes in effects", () => {
  const [count, setCount] = createSignal(0);

  return testEffect((done) =>
    createEffect((run: number = 0) => {
      if (run === 0) {
        expect(count()).toBe(0);
        setCount(1);
      } else if (run === 1) {
        expect(count()).toBe(1);
        done();
      }
      return run + 1;
    })
  );
});

File Organization

src/
├── components/
│   ├── Counter.tsx
│   └── Counter.test.tsx          ← Co-located test files
├── hooks/
│   ├── useCounter.ts
│   └── useCounter.test.ts
├── test-setup.ts                 ← Global test setup
└── __tests__/                    ← Alternative: dedicated test folder
    └── integration/
        └── app.test.tsx

ALWAYS use .test.tsx extension for files containing JSX in tests. Use .test.ts only for pure logic tests without JSX.

Reference Links

Official Sources