Add unit tests for feature detection

Author: rjmurillo

Diff for: tests/EffectiveCSharp.Analyzers.Tests/SupportsTypeTests.cs

@@ -0,0 +1,51 @@
+using EffectiveCSharp.Analyzers.Common;
+using Microsoft.CodeAnalysis;
+
+namespace EffectiveCSharp.Analyzers.Tests;
+
+public class SupportsTypeTests
+{
+    [Fact]
+    public void Supports_FormattableString()
+    {
+        Compilation compilation = CreateCompilation();
+
+        bool result = compilation.SupportsType("System.FormattableString");
+
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void Supports_StringCreate()
+    {
+        Compilation compilation = CreateCompilation();
+
+        bool result = compilation.SupportsType("System.String", "Create");
+
+        Assert.True(result);
+    }
+
+    private static Compilation CreateCompilation()
+    {
+        const string testCode = """
+                                public class C
+                                {
+                                    public void M()
+                                    {
+                                    }
+                                }
+                                """;
+
+        Compilation compilation = CreateCompilation(testCode);
+        return compilation;
+    }
+
+    private static Compilation CreateCompilation(string sourceCode)
+    {
+        return CSharpCompilation.Create(
+            "TestAssembly",
+            new[] { CSharpSyntaxTree.ParseText(sourceCode) },
+            new[] { MetadataReference.CreateFromFile(typeof(object).Assembly.Location) },
+            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
+    }
+}