/frontend-testing

Common Testing Patterns

Frequently used patterns for testing Langflow React components with Jest and React Testing Library.

Query Priority

Use queries in this priority order (most to least preferred):

Query Variants

Examples

// Preferred: query by role
screen.getByRole("button", { name: /save/i });
screen.getByRole("textbox", { name: /search/i });
screen.getByRole("heading", { level: 2 });
screen.getByRole("checkbox", { name: /agree/i });
screen.getByRole("combobox");

// Assert absence
expect(screen.queryByText("Error")).not.toBeInTheDocument();

// Async appearance
const element = await screen.findByText("Loaded");

User Events

Always use @testing-library/user-event over fireEvent:

import userEvent from "@testing-library/user-event";

describe("UserInteractions", () => {
  it("should handle click", async () => {
    const user = userEvent.setup();
    const onClick = jest.fn();

    render(<button onClick={onClick}>Click me</button>);
    await user.click(screen.getByRole("button"));

    expect(onClick).toHaveBeenCalledTimes(1);
  });

  it("should handle typing", async () => {
    const user = userEvent.setup();
    const onChange = jest.fn();

    render(<input onChange={onChange} />);
    await user.type(screen.getByRole("textbox"), "hello");

    expect(onChange).toHaveBeenCalledTimes(5); // One per character
  });

  it("should handle clearing and typing", async () => {
    const user = userEvent.setup();

    render(<input defaultValue="old value" />);
    const input = screen.getByRole("textbox");

    await user.clear(input);
    await user.type(input, "new value");

    expect(input).toHaveValue("new value");
  });

  it("should handle keyboard navigation", async () => {
    const user = userEvent.setup();

    render(
      <div>
        <input data-testid="input-1" />
        <input data-testid="input-2" />
      </div>,
    );

    await user.tab();
    expect(screen.getByTestId("input-1")).toHaveFocus();

    await user.tab();
    expect(screen.getByTestId("input-2")).toHaveFocus();
  });

  it("should handle select/dropdown", async () => {
    const user = userEvent.setup();

    render(
      <select>
        <option value="a">Option A</option>
        <option value="b">Option B</option>
      </select>,
    );

    await user.selectOptions(screen.getByRole("combobox"), "b");
    expect(screen.getByRole("combobox")).toHaveValue("b");
  });

  it("should handle hover", async () => {
    const user = userEvent.setup();
    const onMouseEnter = jest.fn();

    render(<div onMouseEnter={onMouseEnter}>Hover me</div>);
    await user.hover(screen.getByText("Hover me"));

    expect(onMouseEnter).toHaveBeenCalledTimes(1);
  });
});

Form Testing

describe("LoginForm", () => {
  it("should submit form with valid data", async () => {
    const user = userEvent.setup();
    const onSubmit = jest.fn();

    render(<LoginForm onSubmit={onSubmit} />);

    await user.type(screen.getByLabelText(/username/i), "testuser");
    await user.type(screen.getByLabelText(/password/i), "password123");
    await user.click(screen.getByRole("button", { name: /sign in/i }));

    expect(onSubmit).toHaveBeenCalledWith({
      username: "testuser",
      password: "password123",
    });
  });

  it("should show validation errors for empty fields", async () => {
    const user = userEvent.setup();

    render(<LoginForm onSubmit={jest.fn()} />);

    await user.click(screen.getByRole("button", { name: /sign in/i }));

    expect(screen.getByText(/username is required/i)).toBeInTheDocument();
    expect(screen.getByText(/password is required/i)).toBeInTheDocument();
  });

  it("should disable submit button while submitting", async () => {
    const user = userEvent.setup();
    const onSubmit = jest.fn(() => new Promise(() => {})); // Never resolves

    render(<LoginForm onSubmit={onSubmit} />);

    await user.type(screen.getByLabelText(/username/i), "testuser");
    await user.type(screen.getByLabelText(/password/i), "password123");
    await user.click(screen.getByRole("button", { name: /sign in/i }));

    expect(screen.getByRole("button", { name: /sign in/i })).toBeDisabled();
  });
});

Modal/Dialog Testing

Langflow uses Radix UI dialogs:

describe("ConfirmDialog", () => {
  it("should open and close the dialog", async () => {
    const user = userEvent.setup();

    render(<ConfirmDialog trigger={<button>Open</button>} />);

    // Dialog should not be visible initially
    expect(screen.queryByRole("dialog")).not.toBeInTheDocument();

    // Open dialog
    await user.click(screen.getByRole("button", { name: /open/i }));

    // Dialog should be visible
    expect(screen.getByRole("dialog")).toBeInTheDocument();
    expect(screen.getByText(/are you sure/i)).toBeInTheDocument();

    // Close dialog by clicking cancel
    await user.click(screen.getByRole("button", { name: /cancel/i }));

    // Dialog should be hidden
    await waitForElementToBeRemoved(() => screen.queryByRole("dialog"));
  });

  it("should call onConfirm when confirmed", async () => {
    const user = userEvent.setup();
    const onConfirm = jest.fn();

    render(
      <ConfirmDialog trigger={<button>Open</button>} onConfirm={onConfirm} />,
    );

    await user.click(screen.getByRole("button", { name: /open/i }));
    await user.click(screen.getByRole("button", { name: /confirm/i }));

    expect(onConfirm).toHaveBeenCalledTimes(1);
  });
});

Data-Driven Tests (Parameterized)

Use it.each for testing multiple inputs with the same logic:

describe("formatDuration", () => {
  it.each([
    [0, "0s"],
    [500, "0.5s"],
    [1000, "1.0s"],
    [1500, "1.5s"],
    [60000, "1m 0s"],
    [90000, "1m 30s"],
    [3600000, "1h 0m"],
  ])("should format %i ms as %s", (input, expected) => {
    expect(formatDuration(input)).toBe(expected);
  });
});

Named Parameters with Objects

it.each([
  { input: "", expected: false, description: "empty string" },
  { input: "valid@email.com", expected: true, description: "valid email" },
  { input: "no-at-sign", expected: false, description: "missing @" },
  { input: "@no-local", expected: false, description: "missing local part" },
])("should return $expected for $description", ({ input, expected }) => {
  expect(isValidEmail(input)).toBe(expected);
});

Snapshot Testing

Use sparingly -- only for stable, presentational components:

it("should match snapshot", () => {
  const { container } = render(<Badge variant="success" label="Active" />);
  expect(container.firstChild).toMatchSnapshot();
});

Prefer explicit assertions over snapshots. Snapshots are fragile and do not communicate test intent.

Testing Conditional Rendering

describe("StatusBadge", () => {
  it("should render success variant", () => {
    render(<StatusBadge status="success" />);
    expect(screen.getByText("Success")).toBeInTheDocument();
  });

  it("should render error variant", () => {
    render(<StatusBadge status="error" />);
    expect(screen.getByText("Error")).toBeInTheDocument();
  });

  it("should render nothing for unknown status", () => {
    const { container } = render(<StatusBadge status="unknown" />);
    expect(container).toBeEmptyDOMElement();
  });
});

Testing Lists and Tables

describe("ItemList", () => {
  it("should render all items", () => {
    const items = [
      { id: "1", name: "Item 1" },
      { id: "2", name: "Item 2" },
      { id: "3", name: "Item 3" },
    ];

    render(<ItemList items={items} />);

    const listItems = screen.getAllByRole("listitem");
    expect(listItems).toHaveLength(3);
    expect(listItems[0]).toHaveTextContent("Item 1");
    expect(listItems[1]).toHaveTextContent("Item 2");
    expect(listItems[2]).toHaveTextContent("Item 3");
  });

  it("should show empty state when no items", () => {
    render(<ItemList items={[]} />);

    expect(screen.getByText(/no items/i)).toBeInTheDocument();
    expect(screen.queryByRole("listitem")).not.toBeInTheDocument();
  });
});

Testing Tooltips

Langflow uses Radix tooltips which require hover:

it("should show tooltip on hover", async () => {
  const user = userEvent.setup();

  render(<TooltipButton label="Delete" tooltip="Delete this item" />);

  await user.hover(screen.getByRole("button", { name: /delete/i }));

  await waitFor(() => {
    expect(screen.getByRole("tooltip")).toHaveTextContent("Delete this item");
  });
});

Testing Error Boundaries

describe("ErrorBoundary", () => {
  // Suppress console.error for expected errors
  const originalError = console.error;
  beforeAll(() => {
    console.error = jest.fn();
  });
  afterAll(() => {
    console.error = originalError;
  });

  it("should catch errors and show fallback UI", () => {
    const ThrowError = () => {
      throw new Error("Test error");
    };

    render(
      <ErrorBoundary fallback={<div>Something went wrong</div>}>
        <ThrowError />
      </ErrorBoundary>,
    );

    expect(screen.getByText("Something went wrong")).toBeInTheDocument();
  });
});

Testing Custom data-testid Attributes

Langflow components frequently use data-testid for testing. Common patterns:

// Input components
screen.getByTestId("popover-anchor-input-api_key");

// Buttons
screen.getByTestId("sidebar-nav-add_note");

// Modal elements
screen.getByTestId("modal-title");

// Flow elements
screen.getByTestId("handle-source-bottom");

Testing with Zustand Store Updates

it("should react to store changes", async () => {
  render(<NotificationBanner />);

  // Initially no notification
  expect(screen.queryByText("Error occurred")).not.toBeInTheDocument();

  // Update store
  act(() => {
    useAlertStore.setState({
      errorData: { title: "Error occurred", list: [] },
    });
  });

  // Notification should appear
  expect(screen.getByText("Error occurred")).toBeInTheDocument();
});

Cleanup

React Testing Library automatically cleans up after each test (unmounts rendered components). You do not need to call cleanup() manually.

However, you DO need to clean up:

• Fake timers: jest.useRealTimers() in afterEach
• Spies: spy.mockRestore() or jest.restoreAllMocks() in afterEach
• Store state: Reset via store.setState() in beforeEach
• Global overrides: Restore original values in afterEach