Testing

What it does

When your agent uses it

• Jest tests (Desktop/Mobile)
• MSW handlers and testing best practices

Example prompts

• “.test.”
• “.spec.”
• “/tests/”
• “/testing”

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

1. 1toBeVisible() over toBeInTheDocument() — Always. toBeInTheDocument only checks DOM presence; elements can be hidden. Use toBeInTheDocument…
2. 2Search before you create — Before writing any mock, fixture, or helper, rg the codebase. If it exists, import it. If your new mock is…
3. 3Mock external deps only — Never mock child components. Test integration.
4. 4One behavior per test — Name: it("should when ").
5. 5Query priority: getByRole > getByLabelText > getByText > getByTestId (last resort).
6. 6Feature flags via store, never mocked — Use overriddenFeatureFlags in initialState.settings.
7. 7Use existing factories — genAccount() from @ledgerhq/ledger-wallet-framework/mocks/account, getCryptoCurrencyById() from…

What it can do on your machine

Read from SKILL.md and the folder at commit a3861a2. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • pnpm
  • rg

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md. Its commands use pnpm, which can reach the network depending on how they are called.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Testing loads about 1.8k tokens when it runs. Until then it costs about 64 tokens; SKILL.md has 368 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~64

When it runs · the whole SKILL.md, loaded when a task matches

~1.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from LedgerHQ/ledger-live at commit a3861a2, republished under its MIT licence (© LedgerHQ). 368 words, ~1,770 tokens.

name

testing

description

Write unit and integration tests for Ledger Wallet apps. Use for Jest tests (Desktop/Mobile), MSW handlers and testing best practices. Applies to "*.test.*", "*.spec.*", "**/tests/**", "**/__tests__/**", "**/__integrations__/**", "**/jest-setup*"

pnpm test:jest "filename"    # Run specific file
pnpm test:jest               # Run all tests
pnpm test:jest --coverage    # Coverage report

# Coin modules (libs/coin-modules)
pnpm coin:<name> test              # Unit tests
pnpm coin:<name> test "filename"   # Specific file
pnpm coin:<name> test-integ        # Integration tests (slow)

import { render, screen, waitFor } from "tests/testSetup";
import { server } from "tests/server";
import { http, HttpResponse } from "msw";

jest.mock("@ledgerhq/live-common/someService");

describe("MyComponent", () => {
  beforeEach(() => jest.clearAllMocks());

  it("should render title", () => {
    render(<MyComponent title="Test" />);
    expect(screen.getByText("Test")).toBeVisible();
  });

  it("should call onClick when button pressed", async () => {
    const onClick = jest.fn();
    const { user } = render(<MyComponent onClick={onClick} />);
    await user.click(screen.getByRole("button"));
    expect(onClick).toHaveBeenCalledTimes(1);
  });

  it("should display fetched data", async () => {
    server.use(http.get("/api/data", () => HttpResponse.json({ name: "Bitcoin" })));
    render(<MyComponent />);
    await waitFor(() => expect(screen.getByText("Bitcoin")).toBeVisible());
  });
});

import { renderHook, act, waitFor } from "tests/testSetup";

const { result } = renderHook(() => useMyHook());
await act(async () => result.current.increment());
expect(result.current.value).toBe(1);

render(<MyComponent />, {
  initialState: {
    settings: { theme: "dark" },
    accounts: { active: [mockAccount] },
  },
});

render(<MyScreen />, {
  overrideInitialState: (state: State) => ({
    ...state,
    settings: { ...state.settings, blacklistedTokenIds: ["ethereum/erc20/usdt"] },
  }),
});

render(<MyComponent />, {
  initialState: {
    settings: {
      overriddenFeatureFlags: {
        myFlag: { enabled: true, params: { key: "value" } },
      },
    },
  },
});

// External dependency
jest.mock("@ledgerhq/live-common/account/index");
const mockedFn = jest.mocked(getMainAccount);
mockedFn.mockReturnValue(mockAccount);

// ViewModel (MVVM)
jest.mock("../useMyViewModel", () => ({ useMyViewModel: jest.fn() }));
jest.spyOn(UseMyViewModel, "useMyViewModel").mockImplementation(() => ({
  data: mockData,
  isLoading: false,
}));

// MSW override for error case
server.use(http.get("/api/data", () => HttpResponse.json({ error: "Not found" }, { status: 404 })));

# Run BEFORE writing new mocks
rg "yourMockName|yourHelper" tests/ __tests__/ src/ libs/ --type ts

1. Search for existing mocks → 2. Write test → 3. Run test → 4. Fix if fail → 5. Next file

© LedgerHQ, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/testing of LedgerHQ/ledger-live.

Open the folder on GitHubat commit a3861a2