Add capability to add custom replacer to scheme

Closes #463

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Added support extending existing Schemes for customisation
+
 ## [7.0.0.8] - 2024-08-15
 
 ### Added

src/Html2Markdown/Scheme/AbstractScheme.cs

@@ -30,4 +30,9 @@ public IList<IReplacer> Replacers()
     {
         return ReplacerCollection;
     }
+
+    public void AddReplacer(IReplacer replacer)
+    {
+        ReplacerCollection.Add(replacer);
+    }
 }

test/Html2Markdown.Test/Scheme/AbstractSchemeTests.cs

@@ -0,0 +1,106 @@
+using System.Collections.Generic;
+using Html2Markdown.Replacement;
+using Html2Markdown.Scheme;
+
+namespace Html2Markdown.Test.Scheme;
+
+public class AbstractSchemeTests
+{
+    [Test]
+    public void Replacers_WhenCalled_ReturnsReplacerCollection()
+    {
+        // arrange
+        const int expectedCount = 1;
+        var scheme = new TestScheme();
+
+        // act
+        var replacers = scheme.Replacers();
+
+        // assert
+        Assert.That(replacers.Count, Is.EqualTo(expectedCount));
+    }
+
+    [Test]
+    public void Replacers_WhenCalled_ReturnsReplacerCollectionWithTestReplacer()
+    {
+        // arrange
+        var scheme = new TestScheme();
+
+        // act
+        var replacers = scheme.Replacers();
+
+        // assert
+        Assert.That(replacers[0], Is.InstanceOf<TestReplacer>());
+    }
+
+    [Test]
+    public void Replacers_WhenCalled_ReturnsReplacerCollectionWithTestReplacerReplaceMethod()
+    {
+        // arrange
+        const string expected = "test";
+        var scheme = new TestScheme();
+
+        // act
+        var replacers = scheme.Replacers();
+        var result = replacers[0].Replace(string.Empty);
+
+        // assert
+        Assert.That(result, Is.EqualTo(expected));
+    }
+
+    [Test]
+    public void AddReplacer_WhenCalled_AddsReplacerToReplacerCollection()
+    {
+        // arrange
+        const int expectedCount = 2;
+        var scheme = new TestScheme();
+
+        // act
+        scheme.AddReplacer(new TestReplacer());
+        var replacers = scheme.Replacers();
+
+        // assert
+        Assert.That(replacers.Count, Is.EqualTo(expectedCount));
+    }
+
+    [Test]
+    public void AddReplacer_WhenCalled_AddsReplacerToReplacerCollectionWithTestReplacer()
+    {
+        // arrange
+        var scheme = new TestScheme();
+
+        // act
+        scheme.AddReplacer(new TestReplacer());
+        var replacers = scheme.Replacers();
+
+        // assert
+        Assert.That(replacers[1], Is.InstanceOf<TestReplacer>());
+    }
+}
+
+public class TestScheme : AbstractScheme
+{
+    public TestScheme()
+    {
+        AddReplacementGroup(ReplacerCollection, new TestReplacementGroup());
+    }
+}
+
+public class TestReplacementGroup : IReplacementGroup
+{
+    public IEnumerable<IReplacer> Replacers()
+    {
+        return new List<IReplacer>
+        {
+            new TestReplacer()
+        };
+    }
+}
+
+public class TestReplacer : IReplacer
+{
+    public string Replace(string html)
+    {
+        return "test";
+    }
+}