Fix off by one error in small files

Currently there's an off-by-one error when displaying a small file with
fewer rows than the number used in previews (10).  This fixes the
off-by-one and introduces a test to ensure we don't re-introduce it.

fixtures/small-file.csv

@@ -0,0 +1,2 @@
+A,B
+1,2

lib/importer/sheets.js

@@ -156,7 +156,7 @@ exports.GetRows = (session, start=0, count=10) => {
   const rowRange = {
     sheet: session.sheet,
     start: { row: start, column: 0},
-    end: { row: Math.min(start + count - 1, sheetDimensions.rows-1), column: sheetDimensions.columns-1}
+    end: { row: Math.min(start + count, sheetDimensions.rows), column: sheetDimensions.columns-1}
   }
 
   const wantedRows = rowRange.end.row - start;

prototypes/basic/tests/small-file.spec.js

@@ -0,0 +1,96 @@
+import { test, expect } from '@playwright/test';
+
+import * as fixtures from "./helpers/fixtures";
+
+import { UploadPage } from './helpers/upload_page';
+import { SheetSelectorPage } from './helpers/sheet_selector_page';
+import { HeaderSelectorPage } from './helpers/header_selector_page';
+import { FooterSelectorPage } from './helpers/footer_selector_page'
+import { MappingPage } from './helpers/mapping_page'
+
+const path = require('node:path');
+
+// Take a screenshot to help with debugging
+const screenshot = async(page, name) => {
+    await page.screenshot({ path: name, fullPage: true });
+}
+
+test('tiny files', async ({ page }) => {
+    await page.goto('/');
+    await page.getByText('Start now').click();
+
+    // ---------------------------------------------------------------------------
+    // Upload a file
+    await expect(page).toHaveURL(/.upload/)
+
+    const uploadPage = new UploadPage(page)
+    const browseButton = await uploadPage.browseButton()
+
+    await browseButton.click();
+    await browseButton.setInputFiles(fixtures.getFixture('small-file.csv'));
+    await uploadPage.submit();
+
+    // ---------------------------------------------------------------------------
+    // Select sheet
+    await expect(page).toHaveURL(/.select_sheet/)
+
+    const sheets = new SheetSelectorPage(page);
+
+    // There is only a single sheet, it should default be selected and the table
+    // visible
+    const radioButton = await sheets.getRadio('Sheet1')
+    await expect(radioButton).toBeChecked();
+    const vis = await sheets.getTableProperty(0, 'visibility')
+    await expect(vis).toBe('visible')
+
+    // // Check the data is present in the sheet previews
+    const previewRow = await sheets.getTableRow(0, 0)
+    const zerozero = await previewRow.locator("td").nth(0).textContent()
+    const zeroone =  await previewRow.locator("td").nth(1).textContent()
+    await expect(zerozero).toBe("A")
+    await expect(zeroone).toBe("B")
+
+    await sheets.submit()
+
+    // ---------------------------------------------------------------------------
+    // Select some cells for a header row
+    // We will use the entire first row as our selection
+    await expect(page).toHaveURL(/.select_header_row/)
+
+    const headers = new HeaderSelectorPage(page)
+    await headers.select([0,0], [0,1])
+    await headers.submit()
+
+    // // ---------------------------------------------------------------------------
+    // // Do not choose a footer row, just click Skip
+    await expect(page).toHaveURL(/.select_footer_row/)
+
+    const footers = new FooterSelectorPage(page)
+    await footers.skip()
+
+    // // ---------------------------------------------------------------------------
+    // // Perform the mapping after checking the previews here are what we expect
+    await expect(page).toHaveURL(/.mapping/)
+
+    const mapping = new MappingPage(page)
+
+    const expectedColumns = ["A", "B"]
+    const expectedExamples = [
+        "1",
+        "2",
+    ]
+
+    const colNames = await mapping.getColumnNames()
+    expect(colNames).toStrictEqual(expectedColumns)
+
+    const examples = await mapping.getExamples()
+    expect(examples).toStrictEqual(expectedExamples)
+
+    await mapping.setMapping('A', 'Code')
+    await mapping.setMapping('B', 'Name')
+    await mapping.submit()
+
+    // // ---------------------------------------------------------------------------
+    // // Should be on the success page
+    await expect(page).toHaveURL(/.success/)
+});