Addded language identifier tests.

JSMR.Infrastructure/Common/Languages/LanguageIdentifier.cs

@@ -26,6 +26,9 @@ public class LanguageIdentifier : ILanguageIdentifier
 
     public Language GetLanguage(string text)
     {
+        if (string.IsNullOrWhiteSpace(text))
+            return Language.Unknown;
+
         var rankedLanguages = _identifier.Identify(text).Where(x => _languages.Contains(x.Item1.Iso639_3));
         var identifiedLanguage = rankedLanguages.OrderBy(x => x.Item2).FirstOrDefault();
 

JSMR.Tests/Unit/LanguageIdentifierTests.cs

@@ -0,0 +1,21 @@
+using JSMR.Domain.Enums;
+using JSMR.Infrastructure.Common.Languages;
+using Shouldly;
+
+namespace JSMR.Tests.Unit;
+
+public class LanguageIdentifierTests
+{
+    private readonly LanguageIdentifier _languageIdentifier = new();
+
+    [Theory]
+    [InlineData("これは日本語のサンプル文章です。今日はいい天気ですね。", Language.Japanese)]
+    [InlineData("This is an English sample sentence used for language detection.", Language.English)]
+    [InlineData("這是一段中文（繁體）的範例文字，用於語言辨識。", Language.ChineseTraditional)]
+    [InlineData("이것은 한국어 예문으로, 언어 식별을 위한 문장입니다。", Language.Korean)]
+    [InlineData("", Language.Unknown)]
+    public void Identify_Languages(string text, Language expectedLanguage)
+    {
+        _languageIdentifier.GetLanguage(text).ShouldBe(expectedLanguage);
+    }
+}