test(discover): add unit tests for Pagination component

src/plugins/discover/public/application/components/default_discover_table/pagination.test.tsx

@@ -0,0 +1,77 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import React from 'react';
+import { render, screen, fireEvent } from '@testing-library/react';
+import { IntlProvider } from 'react-intl';
+import { Pagination } from './pagination';
+
+const renderPagination = (props: Partial<React.ComponentProps<typeof Pagination>> = {}) => {
+  const defaultProps = {
+    pageCount: 10,
+    activePage: 0,
+    goToPage: jest.fn(),
+    startItem: 1,
+    endItem: 50,
+    totalItems: 500,
+    sampleSize: 500,
+    ...props,
+  };
+  return {
+    ...render(
+      <IntlProvider locale="en">
+        <Pagination {...defaultProps} />
+      </IntlProvider>
+    ),
+    props: defaultProps,
+  };
+};
+
+describe('Pagination', () => {
+  it('renders the pagination container', () => {
+    renderPagination();
+    expect(screen.getByTestId('osdDocTablePagination')).toBeInTheDocument();
+  });
+
+  it('displays the correct item range and total', () => {
+    renderPagination({ startItem: 1, endItem: 50, totalItems: 500 });
+    // FormattedMessage renders "1–50 of 500" (with ndash)
+    const container = screen.getByTestId('osdDocTablePagination');
+    expect(container.textContent).toContain('1');
+    expect(container.textContent).toContain('50');
+    expect(container.textContent).toContain('500');
+  });
+
+  it('calls goToPage when a page is clicked', () => {
+    const goToPage = jest.fn();
+    renderPagination({ goToPage, pageCount: 5, activePage: 0 });
+    // EuiPagination renders page buttons with aria-label "Page X of Y"
+    const page2Button = screen.getByLabelText('Page 2 of 5');
+    fireEvent.click(page2Button);
+    expect(goToPage).toHaveBeenCalledWith(1); // 0-indexed
+  });
+
+  it('shows the sample size warning when endItem >= sampleSize', () => {
+    renderPagination({ endItem: 500, sampleSize: 500 });
+    const container = screen.getByTestId('osdDocTablePagination');
+    expect(container.textContent).toContain('Limited to');
+    expect(container.textContent).toContain('500');
+    expect(container.textContent).toContain('Refine your search');
+  });
+
+  it('does not show the sample size warning when endItem < sampleSize', () => {
+    renderPagination({ endItem: 50, sampleSize: 500 });
+    const container = screen.getByTestId('osdDocTablePagination');
+    expect(container.textContent).not.toContain('Limited to');
+    expect(container.textContent).not.toContain('Refine your search');
+  });
+
+  it('renders the correct number of page buttons', () => {
+    renderPagination({ pageCount: 3 });
+    expect(screen.getByLabelText('Page 1 of 3')).toBeInTheDocument();
+    expect(screen.getByLabelText('Page 2 of 3')).toBeInTheDocument();
+    expect(screen.getByLabelText('Page 3 of 3')).toBeInTheDocument();
+  });
+});