DodoSSH/tests/DodoSSH.Client.App.Layout.Tests/ScreenLayoutTests.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Headless;
using Avalonia.Input;
using Avalonia.Threading;
using Avalonia.VisualTree;
using DodoSSH.Client.App.Views;
using DodoSSH.Client.Domain;
using DodoSSH.Client.Import;
using DodoSSH.Client.Session;
using DodoSSH.Client.Session.Tests;
using DodoSSH.Client.Shell.ViewModels;
using DodoSSH.Client.Ssh;
using DodoSSH.Client.Storage;
using DodoSSH.Client.Terminal;
using DodoSSH.Client.Transfer;
using DodoSSH.Crypto;
using NSubstitute;

namespace DodoSSH.Client.App.Layout.Tests;

/// <summary>
/// Whether each screen fits in the space the window gives it.
/// </summary>
/// <remarks>
/// <para>
/// This suite used to measure one control, <c>VaultColumn</c>, because there was one. The design import
/// split it in two — the host list lives beside the terminal, and everything else in the vault has a screen
/// of its own — and added a titlebar, a nav rail and a status bar. That is five things to measure, and the
/// split is what keeps every one of them measurable: none contains the terminal's WebView, and
/// <c>MainWindow</c> still cannot be laid out here at all, because WebView2's adapter refuses the headless
/// dispatcher's MTA thread. <see cref="LayoutHarnessTests"/> pins that.
/// </para>
/// <para>
/// One test per shape a user can put a screen into, because a shape that is never laid out is a shape never
/// checked. The host sidebar has three — list, list with the editor open, and list folded away — and the
/// vault screen has one per category plus one per editor.
/// </para>
/// <para>
/// A real <c>VaultViewModel</c> over a real unlocked vault, rather than a stand-in. Compiled bindings
/// resolve against the declared data type, so a stand-in would have to be the same type anyway — and the
/// editors' height depends on real content: a key with a real armour block in the box is taller than an
/// empty one.
/// </para>
/// </remarks>
public sealed class ScreenLayoutTests : IAsyncLifetime
{
    private const string Passphrase = "a sufficiently long passphrase";
    private const string ServerUrl = "https://dodossh.example";

    /// <remarks>Far below the shipped profile: nothing here attacks a wrap.</remarks>
    private static readonly Argon2Profile CheapProfile =
        Argon2Profile.FromStoredParameters(memoryKibibytes: 8 * 1024, passes: 1, parallelism: 1);

    private readonly FakeAccountServer server = new();
    private readonly StubKeyBinding keyBinding = new();
    private readonly VaultKnownHostStore knownHosts = new();

    private ClientCacheFactory caches = null!;
    private TerminalWorkspace workspace = null!;
    private VaultSession session = null!;
    private VaultViewModel vault = null!;

    /// <remarks>
    /// Constructed and never started: the sign-out card binds to the shell rather than to a vault, and what
    /// it shows comes from properties a fresh one already answers. Starting it would migrate a cache and
    /// read a profile, neither of which any rectangle here depends on.
    /// </remarks>
    private MainWindowViewModel shell = null!;

    /// <remarks>
    /// Over a substitute factory that is never asked for a session. Every shape measured here is one the
    /// screen is in before a connection exists or after one has failed, which is deliberate: the two panes
    /// are at their widest with the local one full and the remote one carrying its explanation, and a
    /// connected pane is the same template with shorter names in it.
    /// </remarks>
    private TransfersViewModel transfers = null!;

    private static CancellationToken Token => TestContext.Current.CancellationToken;

    /// <inheritdoc />
    public async ValueTask InitializeAsync()
    {
        caches = ClientCacheFactory.ForMemory($"layout-{Guid.CreateVersion7():N}");
        await caches.MigrateAsync(Token);

        await new AccountProvisioner(server, keyBinding, caches, TimeProvider.System, CheapProfile)
            .EnrollAsync(ServerUrl, Passphrase, "laptop", "Personal", Token);

        var outcome = await new SessionOpener(caches, TimeProvider.System).UnlockAsync(Passphrase, Token);
        outcome.IsUnlocked.ShouldBeTrue(outcome.Message);
        session = outcome.Session!;

        // Never started and never connected through: no screen's layout depends on the terminal, and the
        // substitute is here only because the view model's constructor asks for one.
        workspace = new TerminalWorkspace(
            new InMemoryTerminalAssetProvider(new Dictionary<string, TerminalAsset>(StringComparer.Ordinal)),
            Substitute.For<ISshConnectionFactory>(),
            TimeProvider.System);

        await knownHosts.OpenAsync(session, Token);

        // Offline. A null connection is what these screens show on a laptop with no network, and it keeps
        // every sync pass out of a suite that is only measuring rectangles.
        vault = new VaultViewModel(session, workspace, knownHosts, static () => null);

        shell = new MainWindowViewModel(
            new ClientPaths(Path.Combine(Path.GetTempPath(), $"dodossh-layout-{Guid.CreateVersion7():N}")),
            caches,
            workspace,
            knownHosts,
            new UnavailableDeviceKeyStore(),
            static (_, _) => throw new InvalidOperationException("A layout test has no network."),
            TimeProvider.System,
            Substitute.For<ISftpSessionFactory>(),
            CheapProfile);

        transfers = new TransfersViewModel(
            Substitute.For<ISftpSessionFactory>(), TimeProvider.System);

        await SeedAsync();

        // Attached after seeding, so the host picker has something in it and the local pane has listed this
        // machine's home directory — which is what puts real names of real length into the row template.
        transfers.Attach(vault, knownHosts);
    }

    /// <inheritdoc />
    public async ValueTask DisposeAsync()
    {
        await shell.DisposeAsync();
        await transfers.DisposeAsync();
        await vault.DisposeAsync();
        knownHosts.Close();
        await workspace.DisposeAsync();
        await session.DisposeAsync();
        caches.Dispose();
    }

    // ---- The host sidebar ----

    [Fact]
    public async Task TheHostSidebarFitsWithNoEditorOpen()
    {
        await MeasureSidebarAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// The tight one, and the reason this suite still exists. The sidebar is 268 pixels wide against the old
    /// column's 340, and the host editor is the tallest thing in it: six fields, an authentication picker
    /// with a two-line item template, a checkbox, a paragraph of hint text and three buttons, all sharing a
    /// column with the list above them.
    /// </remarks>
    [Fact]
    public async Task TheHostSidebarFitsWithItsEditorOpen()
    {
        vault.SelectedHost = vault.Hosts[0];
        vault.EditSelectedHostCommand.Execute(null);

        vault.EditorAuthenticationChoices.Count
            .ShouldBeGreaterThan(1, "the picker has to be populated for this to measure anything");

        // Measured with a credential selected, because an empty picker is shorter than one showing a
        // qualifier beside a label.
        vault.EditorSelectedAuthentication = vault.EditorAuthenticationChoices
            .First(choice => choice.Kind is AuthenticationKind.Credential);

        await MeasureSidebarAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// Folding the list away is the one thing a user can do to this control that changes which of its parts
    /// is on screen, so it is a shape worth laying out on its own.
    /// </remarks>
    [Fact]
    public async Task TheHostSidebarFitsWithItsListFoldedAway()
    {
        vault.ToggleHostsCommand.Execute(null);
        vault.AreHostsExpanded.ShouldBeFalse();

        await MeasureSidebarAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// Headings are rows in the same list as the hosts, drawn from a different template, and they are the
    /// widest thing in a 268-pixel column: a name, a chevron and a count on one line. Measured with one group
    /// folded, because a folded heading is the shape whose row is on screen without any of its hosts.
    /// </remarks>
    [Fact]
    public async Task TheHostSidebarFitsWithGroupHeadingsInTheList()
    {
        await SeedGroupsAsync(3);

        vault.SidebarRows.OfType<SidebarGroupHeader>().Count()
            .ShouldBe(3, "one heading per group, and no ungrouped heading while nothing is ungrouped");

        vault.ToggleGroupCommand.Execute(vault.SidebarRows.OfType<SidebarGroupHeader>().First());

        await MeasureSidebarAsync(faults => faults.ShouldBeEmpty("with three headings and one folded"));
    }

    /// <remarks>
    /// <para>
    /// The one thing a wrong answer here breaks is unrecoverable from the keyboard: <c>MainWindow</c> takes
    /// the keyboard off the terminal's native child window first and then focuses this target, so a target
    /// that cannot take focus leaves the user with no focused element and no way back except the mouse.
    /// </para>
    /// <para>
    /// Which is why this asserts that focus was <i>taken</i> rather than that the right control was named.
    /// A <c>ListBox</c> is not focusable by default, so the call returns false against a list that has not
    /// asked to be — and <c>Focus()</c> on a collapsed control is a no-op that is not replayed when it is
    /// revealed, which is exactly what the folded-away case would hit.
    /// </para>
    /// </remarks>
    [Fact]
    public async Task TheSidebarsKeyboardTargetTakesFocusInBothOfItsShapes()
    {
        await OnTheSidebarAsync((sidebar, _) =>
        {
            sidebar.KeyboardTarget.ShouldBeSameAs(sidebar.HostList);
            sidebar.KeyboardTarget.Focus().ShouldBeTrue("the list is showing");
        });

        vault.ToggleHostsCommand.Execute(null);

        await OnTheSidebarAsync((sidebar, _) =>
        {
            sidebar.KeyboardTarget.ShouldBeSameAs(sidebar.HostFilter);
            sidebar.KeyboardTarget.Focus().ShouldBeTrue("the list is folded away, so the filter takes it");
        });
    }

    /// <remarks>
    /// The editor open with the list still on screen behind it, which is the state a user is most likely to
    /// leave the sidebar in — so it is the state the keyboard answer most has to hold in.
    /// </remarks>
    [Fact]
    public async Task TheSidebarsKeyboardTargetStillTakesFocusWithTheEditorOpen()
    {
        vault.NewHostCommand.Execute(null);

        await OnTheSidebarAsync((sidebar, _) =>
        {
            sidebar.HostList.IsEffectivelyVisible.ShouldBeTrue();
            sidebar.KeyboardTarget.Focus().ShouldBeTrue();
        });
    }

    /// <remarks>
    /// <para>
    /// The strip along the sidebar's bottom edge with the question in it instead of the three buttons. Its
    /// tallest shape is a host with a terminal open on it, which adds a disclosure the ordinary case has
    /// not got — in a 268-pixel column whose middle is a list that has already taken every spare pixel.
    /// </para>
    /// <para>
    /// Worth measuring rather than assuming, because this is the one card in the application a user cannot
    /// scroll: the sidebar's only <c>ScrollViewer</c> is inside the host list, so a button pushed past the
    /// bottom edge here would leave the question unanswerable in either direction.
    /// </para>
    /// </remarks>
    [Fact]
    public async Task TheHostSidebarFitsWithADeletionInQuestion()
    {
        vault.SelectedHost = vault.Hosts[0];
        vault.SelectedHost.IsConnected = true;

        vault.DeleteHostCommand.Execute(null);
        vault.IsConfirmingDeletion.ShouldBeTrue();
        vault.PendingDeletion.ShouldNotBeNull().HasUsage.ShouldBeTrue("the open terminal is the long shape");

        await MeasureSidebarAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// <para>
    /// What a double-click on a machine does everywhere else, and did not do here: it opens a shell on it.
    /// The gesture is wired in the control rather than bound in the markup, which is exactly the sort of
    /// wiring that compiles whether or not it is connected to anything — so it is worth a test that
    /// performs the gesture.
    /// </para>
    /// <para>
    /// Proved through a connection that is refused before any network is involved. The host is left bound
    /// to a key that has been deleted, which <c>TryBuildAuthentication</c> turns into a sentence on the
    /// status line rather than a socket — so what this asserts is that the command ran, with nothing
    /// timing out to make it flaky.
    /// </para>
    /// </remarks>
    [Fact]
    public async Task DoubleClickingAHostConnectsToIt()
    {
        var keyId = vault.Keys[0].EntityId;

        vault.SelectedHost = vault.Hosts[0];
        vault.EditSelectedHostCommand.Execute(null);
        vault.EditorSelectedAuthentication = vault.EditorAuthenticationChoices
            .Single(choice => choice.Kind is AuthenticationKind.SshKey && choice.EntityId == keyId);
        await vault.SaveHostCommand.ExecuteAsync(null);

        vault.SelectedKey = vault.Keys.Single(row => row.EntityId == keyId);
        vault.DeleteKeyCommand.Execute(null);
        await vault.ConfirmDeleteCommand.ExecuteAsync(null);

        vault.SelectedHost = null;
        vault.Status = string.Empty;

        await OnTheSidebarAsync((sidebar, window) =>
        {
            var row = sidebar.HostList.GetVisualDescendants()
                .OfType<ListBoxItem>()
                .First();

            var centre = row.TranslatePoint(
                new Point(row.Bounds.Width / 2, row.Bounds.Height / 2), window)
                ?? throw new InvalidOperationException("the row is not in this window's tree");

            window.MouseDown(centre, MouseButton.Left);
            window.MouseUp(centre, MouseButton.Left);
            window.MouseDown(centre, MouseButton.Left);
            window.MouseUp(centre, MouseButton.Left);

            Dispatcher.UIThread.RunJobs();

            vault.SelectedHost.ShouldNotBeNull("a press on a row selects it");
            vault.Status.ShouldContain(
                "not in this keychain any more",
                Case.Insensitive,
                "the double-click has to reach the connect command");
        });
    }

    // ---- The hosts screen ----
    //
    // Measurable for the first time. Every rectangle below lived in MainWindow.axaml until the terminal
    // moved out from under it, and nothing in that window can be laid out here — so the connect banner, the
    // two host key prompts and the conflict log had never been through this harness at all. They are also
    // the four worst candidates for that: each appears only in a state somebody has to reproduce by hand.

    [Fact]
    public async Task TheHostsScreenFitsWithNothingToAnnounce()
    {
        await MeasureHostsAsync(faults => faults.ShouldBeEmpty("the ordinary shape"));
    }

    [Fact]
    public async Task TheHostsScreenFitsWithAHostSelected()
    {
        vault.SelectedHost = vault.Hosts[0];

        await MeasureHostsAsync(faults => faults.ShouldBeEmpty("with the overview showing a host"));
    }

    [Fact]
    public async Task TheHostsScreenFitsWhileAHostKeyIsBeingApproved()
    {
        vault.PendingHostKey = new HostKeyPresentation(
            "db.internal", 22, "ssh-ed25519", "SHA256:6dPPMHRQGYRSHXBEmqBBIQVMlBfsAcHRDbmfMPWtpvI");

        await MeasureHostsAsync(faults => faults.ShouldBeEmpty("with the unknown-key prompt up"));
    }

    [Fact]
    public async Task TheHostsScreenFitsWhileAHostKeyIsRefused()
    {
        vault.HostKeyMismatch =
            "db.internal:22 presented ssh-ed25519 SHA256:8jkLPQ2mVvTnBqXfWzYc4RdEuHgNsA1oIpKlZbCxMv0, "
            + "and this keychain has SHA256:6dPPMHRQGYRSHXBEmqBBIQVMlBfsAcHRDbmfMPWtpvI pinned for it.";

        await MeasureHostsAsync(faults => faults.ShouldBeEmpty("with the mismatch refusal up"));
    }

    /// <remarks>
    /// Twenty, because one is not the case that broke. The log sits on an <c>Auto</c> row above the overview,
    /// and an <c>ItemsControl</c> with no ceiling grows for as long as it has rows — so a pass that merged a
    /// vault's worth of items pushed everything below it off the bottom of a screen with nothing to scroll.
    /// It survived as long as it did because this markup was inside the window, where no test could reach it;
    /// finding it is what the extraction was for. The fix is the <c>ScrollViewer</c> and <c>MaxHeight</c> in
    /// <c>HostsScreen.axaml</c>, and this is what holds them there.
    /// </remarks>
    [Fact]
    public async Task TheHostsScreenFitsWithAConflictLogTooLongToShow()
    {
        for (var i = 0; i < 20; i++)
        {
            vault.Conflicts.Add(new ConflictRowViewModel(new ConflictNotice(
                Guid.CreateVersion7(),
                Guid.CreateVersion7(),
                ConflictKind.FieldOverridden,
                $"'host-{i}' was changed on two machines, and the other machine's value was kept.",
                [],
                TimeProvider.System.GetUtcNow())));
        }

        await MeasureHostsAsync(faults => faults.ShouldBeEmpty("with twenty merged conflicts to report"));
    }

    /// <remarks>
    /// The group panel is a row of its own at the foot of this screen, so it competes with the overview above
    /// it for the same column — and it grows sideways as groups are added, which is the direction a
    /// fixed-width column has least of. Six, because that is more than anybody's first three and enough to
    /// need the horizontal scroller rather than to overflow silently.
    /// </remarks>
    [Fact]
    public async Task TheHostsScreenFitsWithMoreGroupsThanTheRowHasRoomFor()
    {
        await SeedGroupsAsync(6);

        await MeasureHostsAsync(faults => faults.ShouldBeEmpty("with six groups along the bottom"));
    }

    /// <remarks>
    /// The question replaces the buttons rather than stacking under them — the same rule the sidebar's own
    /// deletion follows — and it is the taller of the two, because it says how many hosts are about to move.
    /// </remarks>
    [Fact]
    public async Task TheHostsScreenFitsWhileAGroupDeletionIsBeingConfirmed()
    {
        await SeedGroupsAsync(3);

        vault.SelectedGroup = vault.Groups[0];
        vault.DeleteGroupCommand.Execute(null);

        vault.IsConfirmingGroupDeletion.ShouldBeTrue("the question has to be up for this to measure it");

        await MeasureHostsAsync(faults => faults.ShouldBeEmpty("with the group question up"));
    }

    // ---- The vault screen ----

    [Fact]
    public async Task TheVaultScreenFitsInEveryCategory()
    {
        foreach (var section in new[]
        {
            VaultSection.All, VaultSection.Keys, VaultSection.Credentials,
        })
        {
            vault.Section = section;

            await MeasureVaultAsync(faults => faults.ShouldBeEmpty($"the {section} category"));
        }
    }

    /// <remarks>
    /// The tall one: a private key needs a real text area, and the vault screen's detail pane is 244 pixels
    /// wide — the narrowest column any form in this application has to fit into.
    /// </remarks>
    [Fact]
    public async Task TheVaultScreenFitsWithTheKeyEditorOpen()
    {
        vault.NewKeyCommand.Execute(null);
        vault.IsEditingKey.ShouldBeTrue();
        vault.ShowsKeys.ShouldBeTrue("opening an editor has to bring its own category into view");

        vault.KeyEditorPrivateKey = string.Join(
            '\n',
            Enumerable.Repeat("b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gt", 6));

        await MeasureVaultAsync(faults => faults.ShouldBeEmpty());
    }

    [Fact]
    public async Task TheVaultScreenFitsWithThePasswordEditorOpen()
    {
        vault.NewCredentialCommand.Execute(null);
        vault.IsEditingCredential.ShouldBeTrue();
        vault.ShowsCredentials.ShouldBeTrue("opening an editor has to bring its own category into view");

        await MeasureVaultAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// The generate form, in the 244-pixel detail pane — two algorithm buttons side by side plus two
    /// paragraphs of explanation, in the narrowest column in the application. The paragraphs are the risk:
    /// they are what says the file has no passphrase, and a sentence pushed off the bottom is a limitation
    /// nobody was told about.
    /// </remarks>
    [Fact]
    public async Task TheVaultScreenFitsWithTheGenerateFormOpen()
    {
        vault.NewGeneratedKeyCommand.Execute(null);
        vault.IsGeneratingKey.ShouldBeTrue();

        await MeasureVaultAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// Both drop highlights forced on at once, which is a state the screen never actually reaches — the
    /// point is that an overlay covering a whole pane does not change the layout of anything beneath it.
    /// It cannot check the thing most likely to be wrong, which is <c>IsHitTestVisible="False"</c>: an
    /// overlay that hit-tests lays out identically and swallows the events that would clear it. That one is
    /// in docs/manual-checks.md.
    /// </remarks>
    [Fact]
    public async Task TheTransfersScreenFitsWithTheDropHighlightsShowing()
    {
        transfers.IsLocalDropTarget = true;
        transfers.IsRemoteDropRefused = true;

        await MeasureTransfersAsync(faults => faults.ShouldBeEmpty("with a drop in progress"));
    }

    // ---- The import screen ----

    [Fact]
    public async Task TheImportScreenFitsBeforeAnythingHasBeenScanned()
    {
        await MeasureImportAsync(faults => faults.ShouldBeEmpty("the state it opens in"));
    }

    /// <remarks>
    /// The shape with something to decide about: a table of candidate hosts with tickboxes, a warning
    /// block above it, and a footer carrying the sentence that says key files are not read. That sentence
    /// is the one that must not be pushed off the bottom — it is the difference between an import somebody
    /// understands and one they think is broken.
    /// </remarks>
    [Fact]
    public async Task TheImportScreenFitsWithHostsToChooseFromAndWarnings()
    {
        await MeasureImportAsync(
            faults => faults.ShouldBeEmpty("with a scanned list"),
            await ScannedImportAsync());
    }

    // ---- The host keys screen ----

    [Fact]
    public async Task TheHostKeysScreenFitsWithNothingApprovedYet()
    {
        foreach (var pin in vault.KnownHostPins.ToList())
        {
            await knownHosts.ForgetAsync(pin.Host, pin.Port, Token);
        }

        await vault.LoadAsync(Token);
        vault.KnownHostPins.ShouldBeEmpty();

        await MeasurePinsAsync(faults => faults.ShouldBeEmpty("the empty state"));
    }

    /// <remarks>
    /// The shape the column widths were chosen for. A fingerprint is never trimmed — comparing a shortened
    /// one against a published one is not something anybody can do — so this table has one column that
    /// refuses to give ground, and this is what says the rest still fits beside it.
    /// </remarks>
    [Fact]
    public async Task TheHostKeysScreenFitsWithPinsAndOneSelected()
    {
        var pins = new KnownHostsViewModel(vault);
        pins.VisiblePins.ShouldNotBeEmpty("an empty list is the easy case and proves nothing here");
        pins.Selected = pins.VisiblePins[0];

        await MeasurePinsAsync(faults => faults.ShouldBeEmpty("with a pin selected"), pins);
    }

    [Fact]
    public async Task TheHostKeysScreenFitsWhenTheFilterMatchesNothing()
    {
        var pins = new KnownHostsViewModel(vault) { Filter = "no such fingerprint" };
        pins.VisiblePins.ShouldBeEmpty();

        await MeasurePinsAsync(faults => faults.ShouldBeEmpty("with the filter matching nothing"), pins);
    }

    // ---- The logs screen ----

    [Fact]
    public async Task TheLogsScreenFitsWithNeitherLogWrittenTo()
    {
        await MeasureLogsAsync(faults => faults.ShouldBeEmpty("the empty state"), LogSection.Connections);
    }

    /// <remarks>
    /// Six columns in one row, and the two widest — an address and a device name — are both variable. A
    /// connection still open is measured alongside the finished ones because its row carries the longest
    /// value the LASTED column ever holds: the words "still open" rather than a duration.
    /// </remarks>
    [Fact]
    public async Task TheConnectionLogFitsWithALiveRowAndAFinishedOne()
    {
        var logs = await SeedLogsAsync();

        logs.Connections.ShouldNotBeEmpty();
        logs.Connections.Any(row => row.IsLive).ShouldBeTrue("the live row is the wide one");

        await MeasureLogsAsync(
            faults => faults.ShouldBeEmpty("with a live connection above a finished one"),
            LogSection.Connections,
            logs);
    }

    /// <remarks>
    /// The FIELDS column is the one that grows: it is a list of names, and a host has eleven of them.
    /// Measured with an edit that touched several, because one field name fits anywhere.
    /// </remarks>
    [Fact]
    public async Task TheActivityLogFitsWithAnEditThatTouchedSeveralFields()
    {
        var logs = await SeedLogsAsync();

        logs.Section = LogSection.Activity;
        logs.Activity.ShouldNotBeEmpty();

        await MeasureLogsAsync(
            faults => faults.ShouldBeEmpty("with the keychain log showing"), LogSection.Activity, logs);
    }

    // ---- The snippets screen ----

    [Fact]
    public async Task TheSnippetsScreenFitsWithNothingSavedYet()
    {
        vault.Snippets.ShouldBeEmpty("the seed makes none, which is what a new keychain looks like");

        await MeasureSnippetsAsync(faults => faults.ShouldBeEmpty("the empty state"));
    }

    /// <remarks>
    /// The detail pane's longest shape: a multi-line command in a box, its notes, two buttons and the
    /// paragraph saying what a terminal will do with it — in a 300-pixel column. Measured with a snippet
    /// that runs, because that is the one with the extra button.
    /// </remarks>
    [Fact]
    public async Task TheSnippetsScreenFitsWithAMultiLineSnippetSelected()
    {
        await SeedSnippetsAsync();

        var snippets = NewSnippetsScreen(new InsertTarget(1, "prod-db"));
        snippets.Selected = snippets.Visible.Single(row => row.RunsOnInsert);

        await MeasureSnippetsAsync(faults => faults.ShouldBeEmpty("with a running snippet selected"), snippets);
    }

    /// <remarks>
    /// The editor, which is the tallest thing on this screen: a name, a 140-pixel command box, notes, the
    /// checkbox and the paragraph explaining what leaving it off buys.
    /// </remarks>
    [Fact]
    public async Task TheSnippetsScreenFitsWithItsEditorOpen()
    {
        await SeedSnippetsAsync();

        var snippets = NewSnippetsScreen();
        snippets.Selected = snippets.Visible[0];
        snippets.EditCommand.Execute(null);

        snippets.IsEditing.ShouldBeTrue();

        await MeasureSnippetsAsync(faults => faults.ShouldBeEmpty("with the editor open"), snippets);
    }

    [Fact]
    public async Task TheSnippetsScreenFitsWhenTheFilterMatchesNothing()
    {
        await SeedSnippetsAsync();

        var snippets = NewSnippetsScreen();
        snippets.Filter = "no such command";
        snippets.Visible.ShouldBeEmpty();

        await MeasureSnippetsAsync(faults => faults.ShouldBeEmpty("with the filter matching nothing"), snippets);
    }

    /// <remarks>
    /// The detail pane with the question in place of EDIT and DELETE, in its longest shape: a key several
    /// hosts authenticate with, which is three sentences and a box in the narrowest column in the
    /// application.
    /// </remarks>
    [Fact]
    public async Task TheVaultScreenFitsWithADeletionInQuestion()
    {
        var keyId = vault.Keys[0].EntityId;

        foreach (var host in vault.Hosts.Take(4).ToList())
        {
            vault.SelectedHost = host;
            vault.EditSelectedHostCommand.Execute(null);
            vault.EditorSelectedAuthentication = vault.EditorAuthenticationChoices
                .Single(choice => choice.Kind is AuthenticationKind.SshKey && choice.EntityId == keyId);

            await vault.SaveHostCommand.ExecuteAsync(null);
        }

        vault.Section = VaultSection.Keys;
        vault.SelectedVaultItem = vault.VaultItems.Single(row => row.EntityId == keyId);

        vault.DeleteSelectedItemCommand.Execute(null);

        vault.PendingDeletion.ShouldNotBeNull().HasUsage
            .ShouldBeTrue("four bound hosts are what makes this the long shape");

        await OnTheVaultAsync((screen, window) =>
        {
            LayoutHarness.Unreachable(window).ShouldBeEmpty();

            // And it says something. A card whose bindings did not resolve would lay out perfectly as three
            // empty rows, which is the one failure a fit test cannot see: compiled bindings against the
            // wrong data type are a logged message rather than an exception.
            var card = screen.GetVisualDescendants().OfType<ConfirmDeleteCard>().ShouldHaveSingleItem();

            var said = string.Join(
                " ",
                card.GetVisualDescendants().OfType<TextBlock>().Select(text => text.Text));

            said.ShouldContain("key-0", Case.Insensitive, "the question has to name what is going");
            said.ShouldContain("4 hosts authenticate with it");
            said.ShouldContain("no undo");
        });
    }

    /// <remarks>
    /// The rail is the only way to reach a category, so a button that lands on nothing walls off three
    /// quarters of the screen. The fit tests above prove the buttons are inside the window; this proves they
    /// are the size a pointer can find, which a zero-height row in a collapsed border would not be.
    /// </remarks>
    [Fact]
    public async Task TheCategoryRailIsBigEnoughToClick()
    {
        await OnTheVaultAsync((screen, _) =>
        {
            var buttons = screen.GetVisualDescendants()
                .OfType<Button>()
                .Where(button => button.Classes.Contains("cat"))
                .ToList();

            buttons.Count.ShouldBe(4, "one per category that exists");

            foreach (var button in buttons)
            {
                button.Bounds.Height.ShouldBeGreaterThan(20);
                button.Bounds.Width.ShouldBeGreaterThan(120);
            }
        });
    }

    // ---- The transfers screen ----

    /// <remarks>
    /// <para>
    /// The widest thing in this window and the one with the least room to give: two file listings side by
    /// side, each with four columns, and a queue underneath — all inside 826 pixels once the nav rail has
    /// taken its column. The header row is the tight part, because it holds a host picker, a password box,
    /// a button and a chip on one line.
    /// </para>
    /// <para>
    /// Measured disconnected, which is the state the screen opens in and the one where the local pane is at
    /// its fullest: it lists this machine's home directory, so the row template is exercised with real names
    /// of real length rather than with fixtures chosen to fit.
    /// </para>
    /// </remarks>
    [Fact]
    public async Task TheTransfersScreenFitsBeforeAnythingIsConnected()
    {
        await MeasureTransfersAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// <para>
    /// The queue is the half of this screen that only exists once something has been asked for, so a shape
    /// nothing puts a row into is a shape never laid out. Three rows, because the row template changes with
    /// the state: a running one shows a bar and a STOP, a stopped one shows RESUME and DISCARD, and a failed
    /// one carries the server's own sentence in the column the other two put a byte count in.
    /// </para>
    /// <para>
    /// The rows are placed directly rather than driven through the queue. What is being measured is the
    /// template at each state, and running a real transfer to reach those states would put a thread-pool
    /// hand-off and a filesystem in the middle of a test about rectangles. What the queue does is measured in
    /// <c>DodoSSH.Client.Transfer.Tests</c>.
    /// </para>
    /// </remarks>
    [Fact]
    public async Task TheTransfersScreenFitsWithTransfersInTheQueue()
    {
        Enqueue(TransferDirection.Download, "artefact.tar.gz", 402_653_184, 149_000_000,
            TransferState.Running, bytesPerSecond: 6_500_000);

        Enqueue(TransferDirection.Upload, "site-backup-2026-07-30.sql.gz", 8_100_000_000, 3_200_000_000,
            TransferState.Cancelled);

        Enqueue(TransferDirection.Upload, "deploy.sh", 4_096, 0, TransferState.Failed,
            failure: "deploy.sh is already in that directory on the host. Rename or remove it first — "
                + "nothing here overwrites a file that is already there.");

        transfers.Transfers.Count.ShouldBe(3);

        await MeasureTransfersAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// The trust card covers the whole screen, and it is the one thing here a user cannot get past without
    /// pressing something — so a button of its own that fell outside the window would leave the screen
    /// permanently blocked.
    /// </remarks>
    [Fact]
    public async Task TheTransfersScreenFitsWithTheHostKeyCardShowing()
    {
        transfers.PendingHostKey = new HostKeyPresentation(
            "db.internal", 22, "ssh-ed25519", "SHA256:0123456789abcdefghijklmnopqrstuvwxyzABCDEFG");

        await MeasureTransfersAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// The question in front of deleting something on the host, which takes a row out of the remote pane's
    /// column while the listing under it is still showing. A directory, because that is the longer of the
    /// two warnings, and a path deep enough to wrap in a pane a third of the window wide.
    /// </remarks>
    [Fact]
    public async Task TheTransfersScreenFitsWithADeletionInQuestion()
    {
        transfers.PendingRemoteDeletion = new RemoteDeletionRequest(
            "2026-07-30",
            "/srv/releases/site/backups/nightly/2026-07-30",
            IsDirectory: true);

        await MeasureTransfersAsync(faults => faults.ShouldBeEmpty());
    }

    // ---- The chrome ----

    /// <remarks>
    /// <para>
    /// The two constants the whole height budget is subtracted from, held against the markup that declares
    /// them. If either bar grows, every screen gets less room than this suite thinks it does and every
    /// measurement above quietly becomes optimistic.
    /// </para>
    /// <para>
    /// Laid out with no data context, which is the point: these are fixed-height strips and their geometry
    /// must not depend on what is bound into them. A binding that made one of them grow with its contents
    /// would fail here.
    /// </para>
    /// </remarks>
    [Fact]
    public async Task TheChromeIsTheHeightTheBudgetAssumes()
    {
        await LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var titleBar = new TitleBar();
                var titleWindow = LayoutHarness.HostAtMinimumSize(
                    titleBar, LayoutHarness.MinimumWidth, LayoutHarness.TitleBarHeight);

                try
                {
                    titleBar.Bounds.Height.ShouldBe(LayoutHarness.TitleBarHeight);
                    LayoutHarness.Unreachable(titleWindow).ShouldBeEmpty();
                }
                finally
                {
                    titleWindow.Close();
                }

                var statusBar = new StatusBar();
                var statusWindow = LayoutHarness.HostAtMinimumSize(
                    statusBar, LayoutHarness.MinimumWidth, LayoutHarness.StatusBarHeight);

                try
                {
                    statusBar.Bounds.Height.ShouldBe(LayoutHarness.StatusBarHeight);
                }
                finally
                {
                    statusWindow.Close();
                }
            },
            Token);
    }

    /// <remarks>
    /// Eight destinations in a 54-pixel column. The rail runs vertically, so what runs out here is height
    /// rather than width — at the window's minimum the entries have to leave room for each other, which is
    /// the same failure the old four-button selector was one label away from. It got tighter when the host
    /// keys left the keychain screen and became a destination of their own, and tighter again with snippets
    /// and then the logs — which is why the count is asserted rather than left to the fit check: an entry
    /// silently dropping off the bottom would still pass every other assertion here.
    /// </remarks>
    [Fact]
    public async Task TheNavRailHoldsEightDestinationsAtTheWindowsMinimum()
    {
        await LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var rail = new NavRail();
                var window = LayoutHarness.HostAtMinimumSize(
                    rail, LayoutHarness.NavRailWidth, LayoutHarness.ScreenHeight);

                try
                {
                    var buttons = rail.GetVisualDescendants().OfType<Button>().ToList();

                    buttons.Count.ShouldBe(8, "one per screen the rail reaches");

                    foreach (var button in buttons)
                    {
                        button.Bounds.Height.ShouldBeGreaterThan(20);

                        // One pixel narrower than the rail, because the rail draws its own divider down its
                        // right edge and that comes out of the content. Stated exactly rather than as a
                        // lower bound: a button that stopped filling the rail would leave a dead strip
                        // beside every destination, which is precisely the kind of near-miss a bound hides.
                        button.Bounds.Width.ShouldBe(LayoutHarness.NavRailWidth - 1);
                    }

                    LayoutHarness.Unreachable(window).ShouldBeEmpty();
                }
                finally
                {
                    window.Close();
                }
            },
            Token);
    }

    // ---- The unlock screen ----

    /// <remarks>
    /// <para>
    /// The card a locked application is entirely made of, in its two shapes: an ordinary launch, and one
    /// where shells were left running and the disclosure about them appears. It was extracted from
    /// <c>MainWindow.axaml</c> to be measurable at all — that window cannot be shown here, so anything
    /// inside it is unmeasured by construction — and it is the card with the least room to spare.
    /// </para>
    /// <para>
    /// The status line is set to something long on purpose. It is bound to whatever the last thing that
    /// happened said, and the longest of those is a sentence about an expired sign-in, which is exactly the
    /// message this screen is most likely to be carrying on the launch where the extra rows also appear.
    /// </para>
    /// </remarks>
    [Theory]
    [InlineData(0)]
    [InlineData(2)]
    public async Task TheUnlockCardFitsTheCardItIsShownIn(int liveSessions)
    {
        shell.LiveSessionCount = liveSessions;
        shell.CanUnlockWithDevice = true;
        shell.StatusMessage = "Your sign-in has expired, so this machine is offline: the token endpoint "
            + "returned 400: Invalid refresh token. Sign in again from Preferences to start syncing.";

        await MeasureCardAsync(static () => new UnlockCard());
    }

    [Fact]
    public async Task TheUnlockBoxTakesEnterAsUnlock()
    {
        // Enter is how everybody finishes typing a password, and this screen had no answer to it until the
        // gesture below existed: the passphrase box is where locking puts the keyboard, so the one thing a
        // user does without thinking did nothing at all until they found the button.
        //
        // The gesture is what can be asserted; that pressing it unlocks is ShellFlowTests' business,
        // against the command this binds to.
        await LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var card = new UnlockCard { DataContext = shell };
                var window = LayoutHarness.HostAtMinimumSize(
                    card, LayoutHarness.CardContentWidth, LayoutHarness.CardContentHeight);

                try
                {
                    var binding = card.PassphraseBox.KeyBindings.ShouldHaveSingleItem();

                    binding.Gesture.ShouldBe(new KeyGesture(Key.Enter));
                    binding.Command.ShouldBeSameAs(shell.UnlockCommand);
                }
                finally
                {
                    window.Close();
                }
            },
            Token);
    }

    // ---- The sign-out confirmation ----

    /// <remarks>
    /// <para>
    /// The one new card that has to share a screen with an unlock prompt, and the only one whose height
    /// depends on what it is saying: the warning is a sentence about the outbox, and the disclosure about
    /// shells left running appears only when there are some. Both are wrapped paragraphs, which is the
    /// shape that grows.
    /// </para>
    /// <para>
    /// Measured in the space a card gives its contents rather than inside <c>MainWindow</c>, which cannot
    /// be laid out here — see <c>LayoutHarnessTests.WhyTheWindowItselfIsNeverShown</c>. What that leaves
    /// unchecked is the card's own frame, which is a fixed border and a constant padding.
    /// </para>
    /// </remarks>
    [Fact]
    public async Task TheSignOutCardFitsTheCardItIsShownIn()
    {
        // Its tallest shape: a shell left running adds a disclosure box that an ordinary sign-out does not
        // have, an open transfer session adds a line beneath it, and a locked vault carries the longer of
        // the two warnings.
        shell.LiveSessionCount = 1;
        shell.Transfers.IsConnected = true;

        await MeasureCardAsync(static () => new SignOutCard());
    }

    /// <summary>Lays a setup-screen card out in the space <c>Border.card</c> gives its contents.</summary>
    /// <remarks>
    /// The card is <em>built</em> inside the dispatched call rather than passed in already constructed, and
    /// that is not style. Avalonia binds <c>Dispatcher.UIThread</c> to whichever thread first asks for it, so
    /// a control constructed on the test thread before any other test has dispatched makes that thread the
    /// UI thread — and every later property set from the harness's own thread then throws. It depends on the
    /// order the tests happen to run in, which is why it survived until a phase that added new ones.
    /// </remarks>
    private Task MeasureCardAsync(Func<Control> build) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var card = build();
                card.DataContext = shell;

                var window = LayoutHarness.HostAtMinimumSize(
                    card, LayoutHarness.CardContentWidth, LayoutHarness.CardContentHeight);

                try
                {
                    LayoutHarness.Unreachable(window).ShouldBeEmpty();
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    // ---- Helpers ----

    /// <summary>Lays the sidebar out at the width the hosts screen gives it.</summary>
    private Task MeasureSidebarAsync(Action<IReadOnlyList<string>> assert) =>
        OnTheSidebarAsync((_, window) => assert(LayoutHarness.Unreachable(window)));

    private Task OnTheSidebarAsync(Action<HostSidebar, Window> body) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var sidebar = new HostSidebar { DataContext = vault };

                var window = LayoutHarness.HostAtMinimumSize(
                    sidebar, LayoutHarness.HostSidebarWidth, LayoutHarness.ScreenHeight);

                try
                {
                    body(sidebar, window);
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    /// <summary>Lays the hosts screen out at the size it gets beside the nav rail and under the strip.</summary>
    /// <remarks>
    /// The shell is the data context, not the vault — the sidebar is handed the vault from inside the
    /// screen's own markup. <see cref="MainWindowViewModel.Vault"/> is assigned rather than reached through
    /// an unlock, which would be a second enrollment for no extra rectangle.
    /// </remarks>
    private Task MeasureHostsAsync(Action<IReadOnlyList<string>> assert) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                shell.Vault = vault;
                shell.State = ShellState.Unlocked;

                var screen = new HostsScreen { DataContext = shell };

                var window = LayoutHarness.HostAtMinimumSize(
                    screen, LayoutHarness.ScreenWidth, LayoutHarness.ScreenHeight);

                try
                {
                    assert(LayoutHarness.Unreachable(window));
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    /// <summary>Lays the import screen out at the size it gets beside the nav rail.</summary>
    private Task MeasureImportAsync(
        Action<IReadOnlyList<string>> assert,
        ImportViewModel? import = null) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var screen = new ImportScreen
                {
                    DataContext = import ?? new ImportViewModel(vault, new SshConfigLocator()),
                };

                var window = LayoutHarness.HostAtMinimumSize(
                    screen, LayoutHarness.ScreenWidth, LayoutHarness.ScreenHeight);

                try
                {
                    assert(LayoutHarness.Unreachable(window));
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    /// <summary>
    /// An import view model that has scanned a real file, so the table has rows in it.
    /// </summary>
    /// <remarks>
    /// Through a temporary directory rather than by populating the rows directly, because the shape being
    /// measured is what the parser produces — an entry with two warnings under it is taller than one
    /// without, and inventing the rows would measure a layout nothing generates.
    /// </remarks>
    private async Task<ImportViewModel> ScannedImportAsync()
    {
        var directory = Path.Combine(Path.GetTempPath(), $"dodossh-import-{Guid.CreateVersion7():N}");
        Directory.CreateDirectory(directory);

        try
        {
            await File.WriteAllTextAsync(
                Path.Combine(directory, "config"),
                """
                Host *
                  ServerAliveInterval 30

                Host prod-db
                  HostName database.production.internal
                  User deploy
                  Port 2222
                  IdentityFile ~/.ssh/id_ed25519

                Host bastion-eu-west-1
                  HostName bastion.eu-west-1.example.com
                  User ops
                  ProxyCommand nc %h %p
                  Compression yes
                  compression no

                Match host anything
                  User root
                """);

            var import = new ImportViewModel(vault, new SshConfigLocator(directory));

            // Awaited, not fired. ScanCommand reads a file, so executing without awaiting measures an empty
            // table — which is the other test.
            await import.ScanCommand.ExecuteAsync(null);

            import.HasRows.ShouldBeTrue("the fixture has hosts in it");
            import.HasWarnings.ShouldBeTrue("the fixture has a Match block and a wildcard block");

            return import;
        }
        finally
        {
            Directory.Delete(directory, recursive: true);
        }
    }

    /// <summary>Lays the host keys screen out at the size it gets beside the nav rail.</summary>
    private Task MeasurePinsAsync(
        Action<IReadOnlyList<string>> assert,
        KnownHostsViewModel? pins = null) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var screen = new KnownHostsScreen { DataContext = pins ?? new KnownHostsViewModel(vault) };

                var window = LayoutHarness.HostAtMinimumSize(
                    screen, LayoutHarness.ScreenWidth, LayoutHarness.ScreenHeight);

                try
                {
                    assert(LayoutHarness.Unreachable(window));
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    /// <summary>Lays the logs screen out at the size it gets beside the nav rail.</summary>
    private Task MeasureLogsAsync(
        Action<IReadOnlyList<string>> assert,
        LogSection section,
        LogsViewModel? logs = null) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var model = logs ?? NewLogsScreen();
                model.Section = section;

                var screen = new LogsScreen { DataContext = model };

                var window = LayoutHarness.HostAtMinimumSize(
                    screen, LayoutHarness.ScreenWidth, LayoutHarness.ScreenHeight);

                try
                {
                    assert(LayoutHarness.Unreachable(window));
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    private LogsViewModel NewLogsScreen(params LiveConnection[] live) =>
        new(session, () => live);

    /// <summary>
    /// Writes one of each kind of entry and reads them back.
    /// </summary>
    /// <remarks>
    /// Through the repositories the recorders write to, rather than through the recorders themselves: those
    /// write on a background task on purpose, and a layout suite that waited on one would be measuring
    /// rectangles behind a race.
    /// </remarks>
    private async Task<LogsViewModel> SeedLogsAsync()
    {
        await session.ConnectionLog.CreateAsync(
            session.ActiveVaultId,
            new ConnectionLogSecret
            {
                HostLabel = "customer-a-production-database",
                Address = "deployment-account@db-01.customer-a.internal:22022",
                StartedAt = new DateTimeOffset(2026, 7, 30, 9, 15, 0, TimeSpan.Zero),
                Duration = TimeSpan.FromMinutes(74),
                Outcome = ConnectionOutcome.Refused,
                DeviceName = "jaap-jan-workstation",
            },
            Token);

        await session.ActivityLog.CreateAsync(
            session.ActiveVaultId,
            new ActivityLogSecret
            {
                ItemKind = "Host",
                ItemId = Guid.CreateVersion7(),
                ItemLabel = "customer-a-production-database",
                Operation = ActivityOperation.Updated,
                ChangedFields = "Hostname, Port, Username, Options, Group",
                At = new DateTimeOffset(2026, 7, 30, 9, 15, 0, TimeSpan.Zero),
                DeviceName = "jaap-jan-workstation",
            },
            Token);

        var logs = NewLogsScreen(new LiveConnection(
            "customer-a-production-database",
            "deployment-account@db-01.customer-a.internal:22022",
            new DateTimeOffset(2026, 7, 31, 8, 0, 0, TimeSpan.Zero),
            "jaap-jan-workstation"));

        await logs.ReloadAsync(Token);

        return logs;
    }

    /// <summary>Lays the snippets screen out at the size it gets beside the nav rail.</summary>
    /// <remarks>
    /// The insert function throws. Nothing measured here presses a button, and a substitute that returned a
    /// plausible answer would make it possible to write a layout test that quietly exercised the transport.
    /// </remarks>
    private Task MeasureSnippetsAsync(
        Action<IReadOnlyList<string>> assert,
        SnippetsViewModel? snippets = null) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var screen = new SnippetsScreen { DataContext = snippets ?? NewSnippetsScreen() };

                var window = LayoutHarness.HostAtMinimumSize(
                    screen, LayoutHarness.ScreenWidth, LayoutHarness.ScreenHeight);

                try
                {
                    assert(LayoutHarness.Unreachable(window));
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    private SnippetsViewModel NewSnippetsScreen(InsertTarget? target = null) =>
        new(
            vault,
            () => target ?? InsertTarget.None,
            static (_, _, _, _) => throw new InvalidOperationException("A layout test inserts nothing."));

    /// <summary>Lays the transfers screen out at the width it gets beside the nav rail.</summary>
    private Task MeasureTransfersAsync(Action<IReadOnlyList<string>> assert) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var screen = new TransfersScreen { DataContext = transfers };

                var window = LayoutHarness.HostAtMinimumSize(
                    screen, LayoutHarness.ScreenWidth, LayoutHarness.ScreenHeight);

                try
                {
                    assert(LayoutHarness.Unreachable(window));
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    /// <summary>Puts one transfer on the queue in a given state, without moving a byte.</summary>
    private void Enqueue(
        TransferDirection direction,
        string name,
        long length,
        long transferred,
        TransferState state,
        double bytesPerSecond = 0,
        string? failure = null) =>
        transfers.Transfers.Add(new TransferRowViewModel(new TransferSnapshot(
            Guid.CreateVersion7(),
            direction,
            name,
            Path.Combine(Path.GetTempPath(), name),
            SftpPath.Combine("/srv/releases", name),
            length,
            transferred,
            state,
            bytesPerSecond,
            failure)));

    /// <summary>Lays the vault screen out at the width it gets once the nav rail has taken its column.</summary>
    private Task MeasureVaultAsync(Action<IReadOnlyList<string>> assert) =>
        OnTheVaultAsync((_, window) => assert(LayoutHarness.Unreachable(window)));

    private Task OnTheVaultAsync(Action<VaultScreen, Window> body) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var screen = new VaultScreen { DataContext = vault };

                var window = LayoutHarness.HostAtMinimumSize(
                    screen, LayoutHarness.ScreenWidth, LayoutHarness.ScreenHeight);

                try
                {
                    body(screen, window);
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    /// <remarks>
    /// Enough rows in every list that none is empty, because an empty list is the easiest case and the one
    /// least worth certifying.
    /// </remarks>
    private async Task SeedAsync()
    {
        for (var i = 0; i < 6; i++)
        {
            vault.NewHostCommand.Execute(null);
            vault.EditorLabel = $"host-{i}";
            vault.EditorHostname = $"host-{i}.internal";
            vault.EditorUsername = "deploy";
            await vault.SaveHostCommand.ExecuteAsync(null);
        }

        for (var i = 0; i < 4; i++)
        {
            vault.NewKeyCommand.Execute(null);
            vault.KeyEditorLabel = $"key-{i}";
            vault.KeyEditorPrivateKey =
                $"-----BEGIN OPENSSH PRIVATE KEY-----\nMATERIAL-{i}\n-----END OPENSSH PRIVATE KEY-----\n";
            await vault.SaveKeyCommand.ExecuteAsync(null);
        }

        for (var i = 0; i < 3; i++)
        {
            vault.NewCredentialCommand.Execute(null);
            vault.CredentialEditorLabel = $"credential-{i}";
            vault.CredentialEditorPassword = $"password-{i}";
            vault.CredentialEditorUsername = $"account-{i}";
            await vault.SaveCredentialCommand.ExecuteAsync(null);
        }

        // Pins come from approving a fingerprint at connect time, not from an editor, so they are seeded
        // through the store the connect path writes to. Two for one endpoint, because a host offering keys
        // of two algorithms is ordinary and the duplicate is one of the things this list has to show.
        foreach (var (host, algorithm) in new[]
        {
            ("host-0.internal", "ssh-ed25519"),
            ("host-0.internal", "ecdsa-sha2-nistp256"),
            ("gone.internal", "ssh-ed25519"),
        })
        {
            await knownHosts.TrustAsync(
                new HostKeyPresentation(
                    host, 22, algorithm, $"SHA256:{algorithm}-fingerprint-0123456789abcdefghijklmnop"),
                Token);
        }

        // Back to where the vault screen opens, so every test starts from the state a user would see.
        vault.Section = VaultSection.All;

        await vault.LoadAsync(Token);
    }

    /// <summary>
    /// Adds snippets, including the two shapes that decide this screen's height.
    /// </summary>
    /// <remarks>
    /// Not part of <see cref="SeedAsync"/>, so the empty state stays measurable — and because most keychains
    /// have none, which is the shape somebody sees the first time they open the screen.
    /// </remarks>
    private async Task SeedSnippetsAsync()
    {
        await vault.SaveSnippetAsync(
            null,
            new SnippetSecret
            {
                Label = "tail the application log",
                Command = "sudo journalctl -u dodossh-api -f --since '10 minutes ago'",
                Notes = "Ctrl+C to stop.",
            },
            Token);

        await vault.SaveSnippetAsync(
            null,
            new SnippetSecret
            {
                Label = "restart the api",
                Command = "sudo systemctl daemon-reload\nsudo systemctl restart dodossh-api\nsystemctl status dodossh-api --no-pager",
                Notes = "Check the on-call rota before running this in production.",
                RunsOnInsert = true,
            },
            Token);

        vault.Snippets.Count.ShouldBe(2);
    }

    /// <summary>
    /// Adds groups and files the seeded hosts across them.
    /// </summary>
    /// <remarks>
    /// Not part of <see cref="SeedAsync"/>, on purpose. A vault with no groups is what a new one is and what
    /// most of them stay, and it is the shape in which the sidebar draws no headings at all — so it has to
    /// remain the one every other test here measures.
    /// </remarks>
    private async Task SeedGroupsAsync(int count)
    {
        for (var i = 0; i < count; i++)
        {
            vault.GroupEditorLabel = $"customer-{i}-production";
            await vault.SaveGroupCommand.ExecuteAsync(null);
        }

        vault.Groups.Count.ShouldBe(count);

        // Filed through the host editor, which is the only way a user can do it, so this also exercises the
        // picker the sidebar's headings are built out of.
        for (var i = 0; i < vault.Hosts.Count; i++)
        {
            vault.SelectedHost = vault.Hosts[i];
            vault.EditSelectedHostCommand.Execute(null);

            vault.EditorSelectedGroup = vault.EditorGroupChoices
                .First(choice => choice.EntityId == vault.Groups[i % count].EntityId);

            await vault.SaveHostCommand.ExecuteAsync(null);
        }
    }
}