diff --git a/Canon.Tests/Utils.cs b/Canon.Tests/Utils.cs
deleted file mode 100644
index 9babb68..0000000
--- a/Canon.Tests/Utils.cs
+++ /dev/null
@@ -1,16 +0,0 @@
-namespace Canon.Tests;
-
-public static class Utils
-{
-    public static LinkedList<char> GetLinkedList(string content)
-    {
-        LinkedList<char> list = [];
-
-        foreach(char c in content)
-        {
-            list.AddLast(c);
-        }
-
-        return list;
-    }
-}
diff --git a/Canon.Tests/Utils/StringSourceReader.cs b/Canon.Tests/Utils/StringSourceReader.cs
new file mode 100644
index 0000000..f83ea4d
--- /dev/null
+++ b/Canon.Tests/Utils/StringSourceReader.cs
@@ -0,0 +1,47 @@
+using System.Diagnostics.CodeAnalysis;
+using Canon.Core.Abstractions;
+
+namespace Canon.Tests.Utils;
+
+/// <summary>
+/// 从字符串中读取源代码
+/// </summary>
+public sealed class StringSourceReader(string source) : ISourceReader, IDisposable
+{
+    private readonly IEnumerator<char> _enumerator =
+        source.GetEnumerator();
+
+    public uint Line { get; private set; } = 1;
+
+    public uint Pos { get; private set; }
+
+    public string FileName => "string";
+
+    public bool TryReadChar([NotNullWhen(true)] out char? c)
+    {
+        if (Pos != 0 || Line != 1)
+        {
+            // 不是第一次读取
+            if (_enumerator.Current == '\n')
+            {
+                Pos = 0;
+                Line += 1;
+            }
+        }
+
+        if (!_enumerator.MoveNext())
+        {
+            c = null;
+            return false;
+        }
+
+        Pos += 1;
+        c = _enumerator.Current;
+        return true;
+    }
+
+    public void Dispose()
+    {
+        _enumerator.Dispose();
+    }
+}
diff --git a/Canon.Tests/Utils/StringSourceReaderTests.cs b/Canon.Tests/Utils/StringSourceReaderTests.cs
new file mode 100644
index 0000000..21c41fe
--- /dev/null
+++ b/Canon.Tests/Utils/StringSourceReaderTests.cs
@@ -0,0 +1,85 @@
+using Canon.Core.Abstractions;
+
+namespace Canon.Tests.Utils;
+
+public class StringSourceReaderTests
+{
+    [Fact]
+    public void LineFeedTest()
+    {
+        ISourceReader reader = new StringSourceReader("program Main;\nbegin\nend.\n");
+
+        Assert.Equal(0u, reader.Pos);
+        Assert.Equal(1u, reader.Line);
+
+        // program
+        Assert.True(reader.TryReadChar(out char? c));
+        Assert.Equal('p', c);
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out c));
+        Assert.Equal(' ', c);
+
+        // main;
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+        Assert.True(reader.TryReadChar(out char? _));
+
+        Assert.True(reader.TryReadChar(out c));
+        Assert.Equal('\n', c);
+
+        // begin
+        for (uint i = 1; i <= 5; i++)
+        {
+            Assert.True(reader.TryReadChar(out char? _));
+            Assert.Equal(i, reader.Pos);
+            Assert.Equal(2u, reader.Line);
+        }
+
+        // \n
+        Assert.True(reader.TryReadChar(out c));
+        Assert.Equal('\n', c);
+
+        // end.
+        foreach (char i in "end.")
+        {
+            Assert.True(reader.TryReadChar(out c));
+            Assert.Equal(i, c);
+        }
+    }
+
+    [Fact]
+    public void CarriageReturnLineFeedTest()
+    {
+        ISourceReader reader = new StringSourceReader("program Main;\r\nbegin\r\nend.\r\n");
+
+        // program Main;
+        foreach ((char value, uint index) in
+                 "program Main;".Select((value, index) => (value, (uint)index)))
+        {
+            Assert.True(reader.TryReadChar(out char? c));
+            Assert.Equal(value, c);
+            Assert.Equal(index + 1, reader.Pos);
+            Assert.Equal(1u, reader.Line);
+        }
+
+        Assert.True(reader.TryReadChar(out _));
+        Assert.True(reader.TryReadChar(out _));
+
+        // begin
+        foreach ((char value, uint index) in
+                 "begin".Select((value, index) => (value, (uint)index)))
+        {
+            Assert.True(reader.TryReadChar(out char? c));
+            Assert.Equal(value, c);
+            Assert.Equal(index + 1, reader.Pos);
+            Assert.Equal(2u, reader.Line);
+        }
+    }
+}