feat: add getItemTexts to the menu testers (#242) (CP: 25.3)

[vaadin-bot]

This PR cherry-picks changes from the original PR #242 to branch 25.3.

Original PR description

Summary

The menu testers can now tell you which items a menu shows. MenuBarTester, ContextMenuTester and GridContextMenuTester get a getItemTexts() method, so a test can assert the contents of a menu instead of guessing them.

Fixes #216

What changed

This change is purely additive — nothing existing behaves differently.

• getItemTexts() returns the texts of the top level items, and getItemTexts(String, String...) returns the texts of a sub menu, addressed by the same text path that clickItem(String, String...) uses.
• The texts are the ones the browser shows: hidden items are skipped at every level, so the positions match the ones clickItem(int, int...) takes.
• An item created from a component has no text of its own and is reported as an empty string. Use find(Class) to reach such an item.
• Reading items only requires the menu to be visible, not enabled, so the items of a disabled menu bar can still be read. The context menus still have to be open, because their items are not in the UI before that.
• For a grid context menu, the items are the ones offered for the row the menu was opened on, so a dynamic content handler has already run.

Use case

A grid has a per-row action menu, and which actions it offers depends on the row and on the user's permissions. A developer wants to check that a read-only user is not offered "Delete", without clicking anything.

@Test
void readOnlyUser_deleteIsNotOffered() {
    GridContextMenuTester<GridContextMenu<Person>, Person> menu = test(view.menu);

    menu.open(0);

    Assertions.assertIterableEquals(List.of("View", "Export"),
            menu.getItemTexts());
    Assertions.assertIterableEquals(List.of("CSV", "PDF"),
            menu.getItemTexts("Export"));
}

API Changes

com.vaadin.flow.component.menubar.MenuBarTester

// Added
public List<String> getItemTexts() // texts of the visible top level items
public List<String> getItemTexts(String topLevelText, String... nestedItemsText) // texts of the visible items of a sub menu

com.vaadin.flow.component.contextmenu.ContextMenuTester

// Added
public List<String> getItemTexts() // texts of the visible top level items, menu has to be open
public List<String> getItemTexts(String topLevelText, String... nestedItemsText) // texts of the visible items of a sub menu

com.vaadin.flow.component.grid.contextmenu.GridContextMenuTester

// Added
public List<String> getItemTexts() // texts of the visible top level items, menu has to be open
public List<String> getItemTexts(String topLevelText, String... nestedItemsText) // texts of the visible items of a sub menu

com.vaadin.browserless.internal.MenuItemNavigation

// Added
public static List<String> visibleTexts(List<? extends MenuItemBase<?, ?, ?>> items)
public static <C extends ContextMenuBase<C, I, S>, I extends MenuItemBase<C, I, S>, S extends SubMenuBase<C, I, S>> List<String> visibleSubMenuTexts(List<I> rootItems, String topLevelText, String... nestedItemsText)

Test summary

• Reported texts are the visible items in display order; hidden items are left out at the top level and in sub menus.
• The returned positions line up with the ones clickItem(int, int...) uses, verified by clicking an item found by its index.
• A component item is reported as an empty text.
• Asking for the sub menu of an item that has none fails with a clear message, and reading items before a context menu is opened fails.
• A disabled menu bar still reports its items.
• For a grid context menu, the items reflect the row the menu was opened on when a dynamic content handler changes them.

[github-actions]

Test Results

1 517 tests   1 517 ✅  41s ⏱️
  149 suites      0 💤
  149 files        0 ❌

Results for commit 518800a.

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