diff --git a/LrcParser.Tests/Parser/Kar/Lines/KarLyricParserTest.cs b/LrcParser.Tests/Parser/Kar/Lines/KarLyricParserTest.cs
index f5916bb..393b065 100644
--- a/LrcParser.Tests/Parser/Kar/Lines/KarLyricParserTest.cs
+++ b/LrcParser.Tests/Parser/Kar/Lines/KarLyricParserTest.cs
@@ -1,6 +1,7 @@
 // Copyright (c) karaoke.dev <contact@karaoke.dev>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Collections.Generic;
 using LrcParser.Parser.Kar.Lines;
 using LrcParser.Parser.Kar.Metadata;
 using LrcParser.Tests.Helper;
@@ -22,39 +23,115 @@ public void TestCanDecode(string text, bool expected)
         Assert.That(actual, Is.EqualTo(expected));
     }
 
-    [TestCase("[00:17:97]帰[00:18:37]り[00:18:55]道[00:18:94]は[00:19:22]", "帰り道は", new[] { "[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220" })]
-    [TestCase("帰[00:18:37]り[00:18:55]道[00:18:94]は[00:19:22]", "帰り道は", new[] { "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220" })]
-    [TestCase("[00:17:97]帰[00:18:37]り[00:18:55]道[00:18:94]は", "帰り道は", new[] { "[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940" })]
-    [TestCase("帰り道は", "帰り道は", new string[] { })]
-    [TestCase("", "", new string[] { })]
-    [TestCase(null, "", new string[] { })]
-    public void TestDecode(string lyric, string text, string[] timeTags)
+    [TestCaseSource(nameof(testDecodeSource))]
+    public void TestDecode(string lyric, KarLyric expected)
     {
-        var expected = new KarLyric
-        {
-            Text = text,
-            TimeTags = TestCaseTagHelper.ParseTimeTags(timeTags),
-        };
         var actual = Decode(lyric);
 
-        Assert.That(actual.Text, Is.EqualTo(expected.Text));
-        Assert.That(actual.TimeTags, Is.EqualTo(expected.TimeTags));
+        Assert.That(actual, Is.EqualTo(expected));
     }
 
-    [TestCase("帰り道は", new[] { "[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220" }, "[00:17.97]帰[00:18.37]り[00:18.55]道[00:18.94]は[00:19.22]")]
-    [TestCase("帰り道は", new[] { "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220" }, "帰[00:18.37]り[00:18.55]道[00:18.94]は[00:19.22]")]
-    [TestCase("帰り道は", new[] { "[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940" }, "[00:17.97]帰[00:18.37]り[00:18.55]道[00:18.94]は")]
-    [TestCase("帰り道は", new string[] { }, "帰り道は")]
-    [TestCase("", new string[] { }, "")]
-    public void TestEncode(string text, string[] timeTags, string expected)
+    private static IEnumerable<object[]> testDecodeSource => new object[][]
+    {
+        [
+            "[00:17:97]帰[00:18:37]り[00:18:55]道[00:18:94]は[00:19:22]",
+            new KarLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220"]),
+            },
+        ],
+        [
+            "帰[00:18:37]り[00:18:55]道[00:18:94]は[00:19:22]",
+            new KarLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220"]),
+            },
+        ],
+        [
+            "[00:17:97]帰[00:18:37]り[00:18:55]道[00:18:94]は",
+            new KarLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940"]),
+            },
+        ],
+        [
+            "帰り道は",
+            new KarLyric
+            {
+                Text = "帰り道は",
+                TimeTags = [],
+            },
+        ],
+        [
+            "",
+            new KarLyric
+            {
+                Text = "",
+                TimeTags = [],
+            },
+        ],
+        [
+            null!,
+            new KarLyric
+            {
+                Text = "",
+                TimeTags = [],
+            },
+        ],
+    };
+
+    [TestCaseSource(nameof(testEncodeSource))]
+    public void TestEncode(KarLyric lyric, string expected)
     {
-        var lyric = new KarLyric
-        {
-            Text = text,
-            TimeTags = TestCaseTagHelper.ParseTimeTags(timeTags),
-        };
         var actual = Encode(lyric);
 
         Assert.That(actual, Is.EqualTo(expected));
     }
+
+    private static IEnumerable<object[]> testEncodeSource => new object[][]
+    {
+        [
+            new KarLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220"]),
+            },
+            "[00:17.97]帰[00:18.37]り[00:18.55]道[00:18.94]は[00:19.22]",
+        ],
+        [
+            new KarLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220"]),
+            },
+            "帰[00:18.37]り[00:18.55]道[00:18.94]は[00:19.22]",
+        ],
+        [
+            new KarLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940"]),
+            },
+            "[00:17.97]帰[00:18.37]り[00:18.55]道[00:18.94]は",
+        ],
+        [
+            new KarLyric
+            {
+                Text = "帰り道は",
+                TimeTags = [],
+            },
+            "帰り道は",
+        ],
+        [
+            new KarLyric
+            {
+                Text = "",
+                TimeTags = [],
+            },
+            "",
+        ],
+    };
 }
diff --git a/LrcParser.Tests/Parser/Kar/Lines/KarRubyParserTest.cs b/LrcParser.Tests/Parser/Kar/Lines/KarRubyParserTest.cs
index bdab6d9..ec9f5ab 100644
--- a/LrcParser.Tests/Parser/Kar/Lines/KarRubyParserTest.cs
+++ b/LrcParser.Tests/Parser/Kar/Lines/KarRubyParserTest.cs
@@ -1,6 +1,8 @@
 // Copyright (c) karaoke.dev <contact@karaoke.dev>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
+using System.Collections.Generic;
 using LrcParser.Parser.Kar.Lines;
 using LrcParser.Parser.Kar.Metadata;
 using LrcParser.Tests.Helper;
@@ -22,47 +24,137 @@ public void TestCanDecode(string text, bool expected)
         Assert.That(actual, Is.EqualTo(expected));
     }
 
-    [TestCase("@Ruby1=帰,かえ,[00:53:19],[01:24:77]", "帰", "かえ", new string[] { }, 53190, 84770)]
-    [TestCase("@Ruby1=帰,かえ,[01:24:77]", "帰", "かえ", new string[] { }, 84770, null)]
-    [TestCase("@Ruby1=帰,かえ,,[01:24:77]", "帰", "かえ", new string[] { }, null, 84770)]
-    [TestCase("@Ruby1=帰,かえ", "帰", "かえ", new string[] { }, null, null)]
-    [TestCase("@Ruby1=帰,か[00:00:50]え", "帰", "かえ", new[] { "[1,start]:500" }, null, null)]
-    public void TestDecode(string rubyTag, string parent, string ruby, string[] timeTags, int? startTime, int? endTime)
+    [TestCaseSource(nameof(testDecodeSource))]
+    public void TestDecode(string rubyTag, KarRuby expected)
     {
-        var expected = new KarRuby
-        {
-            Parent = parent,
-            Ruby = ruby,
-            TimeTags = TestCaseTagHelper.ParseTimeTags(timeTags),
-            StartTime = startTime,
-            EndTime = endTime,
-        };
         var actual = Decode(rubyTag);
 
-        Assert.That(actual.Ruby, Is.EqualTo(expected.Ruby));
-        Assert.That(actual.Parent, Is.EqualTo(expected.Parent));
-        Assert.That(actual.TimeTags, Is.EqualTo(expected.TimeTags));
-        Assert.That(actual.StartTime, Is.EqualTo(expected.StartTime));
-        Assert.That(actual.EndTime, Is.EqualTo(expected.EndTime));
+        Assert.That(actual, Is.EqualTo(expected));
     }
 
-    [TestCase("帰", "かえ", new string[] { }, 53190, 84770, "@Ruby1=帰,かえ,[00:53.19],[01:24.77]")]
-    [TestCase("帰", "かえ", new string[] { }, 84770, null, "@Ruby1=帰,かえ,[01:24.77]")]
-    [TestCase("帰", "かえ", new string[] { }, null, 84770, "@Ruby1=帰,かえ,,[01:24.77]")]
-    [TestCase("帰", "かえ", new string[] { }, null, null, "@Ruby1=帰,かえ")]
-    [TestCase("帰", "かえ", new[] { "[1,start]:500" }, null, null, "@Ruby1=帰,か[00:00.50]え")]
-    public void TestEncode(string parent, string ruby, string[] timeTags, int? startTime, int? endTime, string expected)
+    private static IEnumerable<object[]> testDecodeSource => new object[][]
+    {
+        [
+            "@Ruby1=帰,かえ,[00:53:19],[01:24:77]",
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(Array.Empty<string>()),
+                StartTime = 53190,
+                EndTime = 84770,
+            },
+        ],
+        [
+            "@Ruby1=帰,かえ,[01:24:77]",
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(Array.Empty<string>()),
+                StartTime = 84770,
+                EndTime = null,
+            },
+        ],
+        [
+            "@Ruby1=帰,かえ,,[01:24:77]",
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(Array.Empty<string>()),
+                StartTime = null,
+                EndTime = 84770,
+            },
+        ],
+        [
+            "@Ruby1=帰,かえ",
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(Array.Empty<string>()),
+                StartTime = null,
+                EndTime = null,
+            },
+        ],
+        [
+            "@Ruby1=帰,か[00:00:50]え",
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(new[] { "[1,start]:500" }),
+                StartTime = null,
+                EndTime = null,
+            },
+        ],
+    };
+
+    [TestCaseSource(nameof(testEncodeSources))]
+    public void TestEncode(KarRuby rubyTag, string expected)
     {
-        var rubyTag = new KarRuby
-        {
-            Parent = parent,
-            Ruby = ruby,
-            TimeTags = TestCaseTagHelper.ParseTimeTags(timeTags),
-            StartTime = startTime,
-            EndTime = endTime,
-        };
         var actual = Encode(rubyTag);
 
         Assert.That(actual, Is.EqualTo(expected));
     }
+
+    private static IEnumerable<object[]> testEncodeSources => new object[][]
+    {
+        [
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = [],
+                StartTime = 53190,
+                EndTime = 84770,
+            },
+            "@Ruby1=帰,かえ,[00:53.19],[01:24.77]",
+        ],
+        [
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = [],
+                StartTime = 84770,
+                EndTime = null,
+            },
+            "@Ruby1=帰,かえ,[01:24.77]",
+        ],
+        [
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = [],
+                StartTime = null,
+                EndTime = 84770,
+            },
+            "@Ruby1=帰,かえ,,[01:24.77]",
+        ],
+        [
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = [],
+                StartTime = null,
+                EndTime = null,
+            },
+            "@Ruby1=帰,かえ",
+        ],
+        [
+            new KarRuby
+            {
+                Parent = "帰",
+                Ruby = "かえ",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[1,start]:500"]),
+                StartTime = null,
+                EndTime = null,
+            },
+            "@Ruby1=帰,か[00:00.50]え",
+        ],
+    };
 }
diff --git a/LrcParser.Tests/Parser/Lines/BaseSingleLineParserTest.cs b/LrcParser.Tests/Parser/Lines/BaseSingleLineParserTest.cs
index a73facc..08b0386 100644
--- a/LrcParser.Tests/Parser/Lines/BaseSingleLineParserTest.cs
+++ b/LrcParser.Tests/Parser/Lines/BaseSingleLineParserTest.cs
@@ -1,11 +1,13 @@
 // Copyright (c) karaoke.dev <contact@karaoke.dev>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using LrcParser.Parser.Lines;
 
 namespace LrcParser.Tests.Parser.Lines;
 
-public class BaseSingleLineParserTest<TParser, TModel> where TParser : SingleLineParser<TModel>, new() where TModel : class
+public class BaseSingleLineParserTest<TParser, TModel>
+    where TParser : SingleLineParser<TModel>, new() where TModel : struct, IEquatable<TModel>
 {
     protected bool CanDecode(string text) => new TParser().CanDecode(text);
 
diff --git a/LrcParser.Tests/Parser/Lrc/Lines/LrcLyricParserTest.cs b/LrcParser.Tests/Parser/Lrc/Lines/LrcLyricParserTest.cs
index 517f38f..333bf3e 100644
--- a/LrcParser.Tests/Parser/Lrc/Lines/LrcLyricParserTest.cs
+++ b/LrcParser.Tests/Parser/Lrc/Lines/LrcLyricParserTest.cs
@@ -1,6 +1,7 @@
 // Copyright (c) karaoke.dev <contact@karaoke.dev>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Collections.Generic;
 using LrcParser.Parser.Lrc.Lines;
 using LrcParser.Parser.Lrc.Metadata;
 using LrcParser.Tests.Helper;
@@ -15,46 +16,121 @@ public class LrcLyricParserTest : BaseSingleLineParserTest<LrcLyricParser, LrcLy
     [TestCase("karaoke", true)]
     [TestCase("", false)]
     [TestCase(null, false)]
-    [TestCase("@Ruby1=帰,かえ", true)] // will take off this if no other parser to process this line.
     public void TestCanDecode(string text, bool expected)
     {
         var actual = CanDecode(text);
         Assert.That(actual, Is.EqualTo(expected));
     }
 
-    [TestCase("[00:17:97]帰[00:18:37]り[00:18:55]道[00:18:94]は[00:19:22]", "帰り道は", new[] { "[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220" })]
-    [TestCase("帰[00:18:37]り[00:18:55]道[00:18:94]は[00:19:22]", "帰り道は", new[] { "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220" })]
-    [TestCase("[00:17:97]帰[00:18:37]り[00:18:55]道[00:18:94]は", "帰り道は", new[] { "[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940" })]
-    [TestCase("帰り道は", "帰り道は", new string[] { })]
-    [TestCase("", "", new string[] { })]
-    [TestCase(null, "", new string[] { })]
-    public void TestDecode(string lyric, string text, string[] timeTags)
+    [TestCaseSource(nameof(testDecodeSource))]
+    public void TestDecode(string lyric, LrcLyric expected)
     {
-        var expected = new LrcLyric
-        {
-            Text = text,
-            TimeTags = TestCaseTagHelper.ParseTimeTags(timeTags),
-        };
         var actual = Decode(lyric);
 
-        Assert.That(actual.Text, Is.EqualTo(expected.Text));
-        Assert.That(actual.TimeTags, Is.EqualTo(expected.TimeTags));
+        Assert.That(actual, Is.EqualTo(expected));
     }
 
-    [TestCase("帰り道は", new[] { "[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220" }, "[00:17.97]帰[00:18.37]り[00:18.55]道[00:18.94]は[00:19.22]")]
-    [TestCase("帰り道は", new[] { "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220" }, "帰[00:18.37]り[00:18.55]道[00:18.94]は[00:19.22]")]
-    [TestCase("帰り道は", new[] { "[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940" }, "[00:17.97]帰[00:18.37]り[00:18.55]道[00:18.94]は")]
-    [TestCase("帰り道は", new string[] { }, "帰り道は")]
-    [TestCase("", new string[] { }, "")]
-    public void TestEncode(string text, string[] timeTags, string expected)
+    private static IEnumerable<object[]> testDecodeSource => new object[][]
+    {
+        [
+            "[00:17:97]帰[00:18:37]り[00:18:55]道[00:18:94]は[00:19:22]",
+            new LrcLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220"]),
+            },
+        ],
+        [
+            "帰[00:18:37]り[00:18:55]道[00:18:94]は[00:19:22]",
+            new LrcLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220"]),
+            },
+        ],
+        [
+            "[00:17:97]帰[00:18:37]り[00:18:55]道[00:18:94]は",
+            new LrcLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940"]),
+            },
+        ],
+        [
+            "帰り道は",
+            new LrcLyric
+            {
+                Text = "帰り道は",
+                TimeTags = [],
+            },
+        ],
+        [
+            "",
+            new LrcLyric
+            {
+                Text = "",
+                TimeTags = [],
+            },
+        ],
+        [
+            null!,
+            new LrcLyric
+            {
+                Text = "",
+                TimeTags = [],
+            },
+        ],
+    };
+
+    [TestCaseSource(nameof(testEncodeSource))]
+    public void TestEncode(LrcLyric lyric, string expected)
     {
-        var lyric = new LrcLyric
-        {
-            Text = text,
-            TimeTags = TestCaseTagHelper.ParseTimeTags(timeTags),
-        };
         var actual = Encode(lyric);
 
         Assert.That(actual, Is.EqualTo(expected));
     }
+
+    private static IEnumerable<object[]> testEncodeSource => new object[][]
+    {
+        [
+            new LrcLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220"]),
+            },
+            "[00:17.97]帰[00:18.37]り[00:18.55]道[00:18.94]は[00:19.22]",
+        ],
+        [
+            new LrcLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[1,start]:18370", "[2,start]:18550", "[3,start]:18940", "[3,end]:19220"]),
+            },
+            "帰[00:18.37]り[00:18.55]道[00:18.94]は[00:19.22]",
+        ],
+        [
+            new LrcLyric
+            {
+                Text = "帰り道は",
+                TimeTags = TestCaseTagHelper.ParseTimeTags(["[0,start]:17970", "[1,start]:18370", "[2,start]:18550", "[3,start]:18940"]),
+            },
+            "[00:17.97]帰[00:18.37]り[00:18.55]道[00:18.94]は",
+        ],
+        [
+            new LrcLyric
+            {
+                Text = "帰り道は",
+                TimeTags = [],
+            },
+            "帰り道は",
+        ],
+        [
+            new LrcLyric
+            {
+                Text = "",
+                TimeTags = [],
+            },
+            "",
+        ],
+    };
 }
diff --git a/LrcParser.Tests/Parser/LyricParserTest.cs b/LrcParser.Tests/Parser/LyricParserTest.cs
index 8664f3e..7581301 100644
--- a/LrcParser.Tests/Parser/LyricParserTest.cs
+++ b/LrcParser.Tests/Parser/LyricParserTest.cs
@@ -1,6 +1,7 @@
 // Copyright (c) karaoke.dev <contact@karaoke.dev>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using LrcParser.Model;
@@ -45,13 +46,13 @@ public TestLyricParser()
 
         protected override Song PostProcess(List<object> values)
         {
-            var lines = values.OfType<string>();
+            var lines = values.OfType<Line>();
 
             return new Song
             {
                 Lyrics = lines.Select(l => new Lyric
                 {
-                    Text = l,
+                    Text = l.Text,
                 }).ToList(),
             };
         }
@@ -60,14 +61,31 @@ protected override IEnumerable<object> PreProcess(Song song)
             => song.Lyrics.Select(lyric => lyric.Text);
     }
 
-    private class TestLineParser : SingleLineParser<string>
+    private class TestLineParser : SingleLineParser<Line>
     {
         public override bool CanDecode(string text)
             => true;
 
-        public override string Decode(string text) => text;
+        public override Line Decode(string text) => new()
+        {
+            Text = text,
+        };
+
+        public override string Encode(Line component, int index)
+            => $"index:{index}, value: {component.Text}";
+    }
+
+    private struct Line : IEquatable<Line>
+    {
+        public Line()
+        {
+        }
+
+        public string Text { get; set; } = string.Empty;
 
-        public override string Encode(string component, int index)
-            => $"index:{index}, value: {component}";
+        public bool Equals(Line other)
+        {
+            return Text == other.Text;
+        }
     }
 }
diff --git a/LrcParser/Model/Lyric.cs b/LrcParser/Model/Lyric.cs
index e4259f1..6be44bb 100644
--- a/LrcParser/Model/Lyric.cs
+++ b/LrcParser/Model/Lyric.cs
@@ -8,7 +8,7 @@ public class Lyric
     /// <summary>
     /// Text
     /// </summary>
-    public string Text { get; set; } = "";
+    public string Text { get; set; } = string.Empty;
 
     /// <summary>
     /// Time tags
diff --git a/LrcParser/Model/RubyTag.cs b/LrcParser/Model/RubyTag.cs
index c1e0daf..7a91133 100644
--- a/LrcParser/Model/RubyTag.cs
+++ b/LrcParser/Model/RubyTag.cs
@@ -5,7 +5,7 @@ namespace LrcParser.Model;
 
 public class RubyTag
 {
-    public string Text { get; set; } = "";
+    public string Text { get; set; } = string.Empty;
 
     /// <summary>
     /// Time tags
diff --git a/LrcParser/Parser/Kar/Metadata/KarLyric.cs b/LrcParser/Parser/Kar/Metadata/KarLyric.cs
index 997b4f7..0142a0e 100644
--- a/LrcParser/Parser/Kar/Metadata/KarLyric.cs
+++ b/LrcParser/Parser/Kar/Metadata/KarLyric.cs
@@ -5,15 +5,24 @@
 
 namespace LrcParser.Parser.Kar.Metadata;
 
-public class KarLyric
+public struct KarLyric : IEquatable<KarLyric>
 {
+    public KarLyric()
+    {
+    }
+
     /// <summary>
     /// Text
     /// </summary>
-    public string Text { get; set; } = "";
+    public string Text { get; set; } = string.Empty;
 
     /// <summary>
     /// Time tags
     /// </summary>
     public SortedDictionary<TextIndex, int> TimeTags { get; set; } = new();
+
+    public bool Equals(KarLyric other)
+    {
+        return Text == other.Text && TimeTags.SequenceEqual(other.TimeTags);
+    }
 }
diff --git a/LrcParser/Parser/Kar/Metadata/KarRuby.cs b/LrcParser/Parser/Kar/Metadata/KarRuby.cs
index fcc4470..3a9f962 100644
--- a/LrcParser/Parser/Kar/Metadata/KarRuby.cs
+++ b/LrcParser/Parser/Kar/Metadata/KarRuby.cs
@@ -13,17 +13,21 @@ namespace LrcParser.Parser.Kar.Metadata;
 /// @Ruby25=時,じか,,[00:38:45]
 /// @Ruby49=時,とき,[00:38:45],[01:04:49]
 /// </example>
-public class KarRuby
+public struct KarRuby : IEquatable<KarRuby>
 {
+    public KarRuby()
+    {
+    }
+
     /// <summary>
     /// Parent kanji
     /// </summary>
-    public string Parent { get; set; } = "";
+    public string Parent { get; set; } = string.Empty;
 
     /// <summary>
     /// Ruby
     /// </summary>
-    public string Ruby { get; set; } = "";
+    public string Ruby { get; set; } = string.Empty;
 
     /// <summary>
     /// Time tags
@@ -33,10 +37,19 @@ public class KarRuby
     /// <summary>
     /// Start position
     /// </summary>
-    public int? StartTime { get; set; }
+    public int? StartTime { get; set; } = null;
 
     /// <summary>
     /// End position
     /// </summary>
-    public int? EndTime { get; set; }
+    public int? EndTime { get; set; } = null;
+
+    public bool Equals(KarRuby other)
+    {
+        return Parent == other.Parent
+               && Ruby == other.Ruby
+               && TimeTags.SequenceEqual(other.TimeTags)
+               && StartTime == other.StartTime
+               && EndTime == other.EndTime;
+    }
 }
diff --git a/LrcParser/Parser/Kar/Utils/KarTimedTextUtils.cs b/LrcParser/Parser/Kar/Utils/KarTimedTextUtils.cs
index 78cd695..1d6dffb 100644
--- a/LrcParser/Parser/Kar/Utils/KarTimedTextUtils.cs
+++ b/LrcParser/Parser/Kar/Utils/KarTimedTextUtils.cs
@@ -21,7 +21,7 @@ internal static Tuple<string, SortedDictionary<TextIndex, int>> TimedTextToObjec
 
         var startIndex = 0;
 
-        var text = "";
+        var text = string.Empty;
         var timeTags = new SortedDictionary<TextIndex, int>();
 
         foreach (var match in matchTimeTags.ToArray())
diff --git a/LrcParser/Parser/Lines/SingleLineParser.cs b/LrcParser/Parser/Lines/SingleLineParser.cs
index 82fd333..f8f8718 100644
--- a/LrcParser/Parser/Lines/SingleLineParser.cs
+++ b/LrcParser/Parser/Lines/SingleLineParser.cs
@@ -7,7 +7,7 @@ namespace LrcParser.Parser.Lines;
 /// Base component pass string
 /// </inheritdoc>
 /// <typeparam name="T">Encode and decode object type</typeparam>
-public abstract class SingleLineParser<T> : ISingleLineParser where T : class
+public abstract class SingleLineParser<T> : ISingleLineParser where T : struct, IEquatable<T>
 {
     public abstract bool CanDecode(string text);
 
diff --git a/LrcParser/Parser/Lrc/Metadata/LrcLyric.cs b/LrcParser/Parser/Lrc/Metadata/LrcLyric.cs
index 21f3aa9..3d12e20 100644
--- a/LrcParser/Parser/Lrc/Metadata/LrcLyric.cs
+++ b/LrcParser/Parser/Lrc/Metadata/LrcLyric.cs
@@ -5,15 +5,24 @@
 
 namespace LrcParser.Parser.Lrc.Metadata;
 
-public class LrcLyric
+public struct LrcLyric : IEquatable<LrcLyric>
 {
+    public LrcLyric()
+    {
+    }
+
     /// <summary>
     /// Text
     /// </summary>
-    public string Text { get; set; } = "";
+    public string Text { get; set; } = string.Empty;
 
     /// <summary>
     /// Time tags
     /// </summary>
     public SortedDictionary<TextIndex, int> TimeTags { get; set; } = new();
+
+    public bool Equals(LrcLyric other)
+    {
+        return Text == other.Text && TimeTags.SequenceEqual(other.TimeTags);
+    }
 }
diff --git a/LrcParser/Parser/Lrc/Utils/LrcTimedTextUtils.cs b/LrcParser/Parser/Lrc/Utils/LrcTimedTextUtils.cs
index 5c27775..6ce012b 100644
--- a/LrcParser/Parser/Lrc/Utils/LrcTimedTextUtils.cs
+++ b/LrcParser/Parser/Lrc/Utils/LrcTimedTextUtils.cs
@@ -21,7 +21,7 @@ internal static Tuple<string, SortedDictionary<TextIndex, int>> TimedTextToObjec
 
         var startIndex = 0;
 
-        var text = "";
+        var text = string.Empty;
         var timeTags = new SortedDictionary<TextIndex, int>();
 
         foreach (var match in matchTimeTags.ToArray())