test(07-08): add export and ViewModel unit tests

- UserAccessCsvExportServiceTests (5): summary section, data header, RFC 4180
  quote escaping, 7-column count, WriteSingleFileAsync multi-user output
- UserAccessHtmlExportServiceTests (7): DOCTYPE, stats cards, dual-view sections,
  access type badges, filterTable JS, toggleView JS, HTML entity encoding
- UserAccessAuditViewModelTests (8): AuditUsersAsync invocation, results population,
  summary properties computation, tenant switch reset, GlobalSitesChanged update,
  override guard, CanExport false/true states

SharepointToolbox.Tests/Services/Export/UserAccessCsvExportServiceTests.cs

@@ -0,0 +1,158 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using SharepointToolbox.Core.Models;
+using SharepointToolbox.Services.Export;
+
+namespace SharepointToolbox.Tests.Services.Export;
+
+/// <summary>
+/// Unit tests for UserAccessCsvExportService (Phase 7 Plan 08).
+/// Verifies: summary section, column count, RFC 4180 escaping, per-user content.
+/// </summary>
+public class UserAccessCsvExportServiceTests
+{
+    // ── Helper factory ────────────────────────────────────────────────────────
+
+    private static UserAccessEntry MakeEntry(
+        string userDisplay = "Alice Smith",
+        string userLogin = "alice@contoso.com",
+        string siteUrl = "https://contoso.sharepoint.com",
+        string siteTitle = "Contoso",
+        string objectType = "List",
+        string objectTitle = "Docs",
+        string objectUrl = "https://contoso.sharepoint.com/Docs",
+        string permLevel = "Read",
+        AccessType accessType = AccessType.Direct,
+        string grantedThrough = "Direct Permissions",
+        bool isHighPrivilege = false,
+        bool isExternal = false) =>
+        new(userDisplay, userLogin, siteUrl, siteTitle, objectType, objectTitle, objectUrl,
+            permLevel, accessType, grantedThrough, isHighPrivilege, isExternal);
+
+    private static readonly UserAccessEntry DefaultEntry = MakeEntry();
+
+    // ── Test 1: BuildCsv includes summary section ─────────────────────────────
+
+    [Fact]
+    public void BuildCsv_includes_summary_section()
+    {
+        var svc = new UserAccessCsvExportService();
+        var csv = svc.BuildCsv("Alice Smith", "alice@contoso.com", new[] { DefaultEntry });
+
+        Assert.Contains("User Access Audit Report", csv);
+        Assert.Contains("Alice Smith", csv);
+        Assert.Contains("alice@contoso.com", csv);
+        Assert.Contains("Total Accesses", csv);
+        Assert.Contains("Sites", csv);
+    }
+
+    // ── Test 2: BuildCsv includes data header line ────────────────────────────
+
+    [Fact]
+    public void BuildCsv_includes_data_header()
+    {
+        var svc = new UserAccessCsvExportService();
+        var csv = svc.BuildCsv("Alice Smith", "alice@contoso.com", new[] { DefaultEntry });
+
+        Assert.Contains("Site", csv);
+        Assert.Contains("Object Type", csv);
+        Assert.Contains("Object", csv);
+        Assert.Contains("Permission Level", csv);
+        Assert.Contains("Access Type", csv);
+        Assert.Contains("Granted Through", csv);
+    }
+
+    // ── Test 3: BuildCsv escapes double quotes (RFC 4180) ─────────────────────
+
+    [Fact]
+    public void BuildCsv_escapes_quotes()
+    {
+        var entryWithQuotes = MakeEntry(objectTitle: "Document \"Template\" Library");
+        var svc = new UserAccessCsvExportService();
+        var csv = svc.BuildCsv("Alice", "alice@contoso.com", new[] { entryWithQuotes });
+
+        // RFC 4180: double quotes inside a quoted field are doubled
+        Assert.Contains("\"\"Template\"\"", csv);
+    }
+
+    // ── Test 4: BuildCsv data rows have correct column count ──────────────────
+
+    [Fact]
+    public void BuildCsv_correct_column_count()
+    {
+        var svc = new UserAccessCsvExportService();
+        var csv = svc.BuildCsv("Alice", "alice@contoso.com", new[] { DefaultEntry });
+
+        // Find the header row and count its quoted comma-separated fields
+        // Header is: "Site","Object Type","Object","URL","Permission Level","Access Type","Granted Through"
+        // That is 7 fields.
+        var lines = csv.Split('\n', StringSplitOptions.RemoveEmptyEntries);
+
+        // Find a data row (after the blank line separating summary from data)
+        // Data rows contain the entry content (not the header line itself)
+        // We want to count fields in the header row:
+        var headerLine = lines.FirstOrDefault(l => l.Contains("\"Site\",\"Object Type\""));
+        Assert.NotNull(headerLine);
+
+        // Count comma-separated quoted fields: split by "," boundary
+        var fields = CountCsvFields(headerLine!);
+        Assert.Equal(7, fields);
+    }
+
+    // ── Test 5: WriteSingleFileAsync includes entries for all users ───────────
+
+    [Fact]
+    public async Task WriteSingleFileAsync_includes_all_users()
+    {
+        var alice = MakeEntry(userDisplay: "Alice", userLogin: "alice@contoso.com");
+        var bob   = MakeEntry(userDisplay: "Bob",   userLogin: "bob@contoso.com");
+
+        var svc = new UserAccessCsvExportService();
+        var tmpFile = Path.GetTempFileName();
+        try
+        {
+            await svc.WriteSingleFileAsync(new[] { alice, bob }, tmpFile, CancellationToken.None);
+            var content = await File.ReadAllTextAsync(tmpFile);
+
+            Assert.Contains("alice@contoso.com", content);
+            Assert.Contains("bob@contoso.com", content);
+            Assert.Contains("Users Audited", content);
+        }
+        finally
+        {
+            File.Delete(tmpFile);
+        }
+    }
+
+    // ── Private helpers ───────────────────────────────────────────────────────
+
+    /// <summary>
+    /// Counts the number of comma-separated fields in a CSV line by stripping
+    /// surrounding quotes from each field.
+    /// </summary>
+    private static int CountCsvFields(string line)
+    {
+        // Simple RFC 4180 field counter — works for well-formed quoted fields
+        int count = 1;
+        bool inQuotes = false;
+        for (int i = 0; i < line.Length; i++)
+        {
+            char c = line[i];
+            if (c == '"')
+            {
+                if (inQuotes && i + 1 < line.Length && line[i + 1] == '"')
+                    i++; // skip escaped quote
+                else
+                    inQuotes = !inQuotes;
+            }
+            else if (c == ',' && !inQuotes)
+            {
+                count++;
+            }
+        }
+        return count;
+    }
+}