Added the choice between formal and informal address to the whole app (#1200)

app/Tests/Settings/AddressFormSettingsTests.cs

@@ -0,0 +1,29 @@
+using AIStudio.Settings;
+using AIStudio.Settings.DataModel;
+
+namespace AIStudio.Tests.Settings;
+
+/// <summary>
+/// Checks the setting for how the texts of AI Studio address the person.
+/// </summary>
+/// <remarks>
+/// Only languages with a formal and an informal address, such as German, offer the choice; see
+/// LanguagePluginExtensions.HasInformalAddress.
+/// </remarks>
+[TestFixture]
+public sealed class AddressFormSettingsTests
+{
+    [Test]
+    public void NewSettingsAddressFormally()
+    {
+        Assert.That(new DataApp().AddressForm, Is.EqualTo(AddressForm.FORMAL), "The texts of AI Studio addressed everybody formally before the setting existed.");
+    }
+
+    [Test]
+    public void TheSettingsOfferEveryFormOfAddress()
+    {
+        var forms = ConfigurationSelectDataFactory.GetAddressFormData().Select(data => data.Value);
+
+        Assert.That(forms, Is.EquivalentTo(Enum.GetValues<AddressForm>()));
+    }
+}