feat: improve TryGetFirstDescendent logic

Author: Meir017

src/FluentAssertions.Analyzers.Tests/Tips/CollectionTests.cs

@@ -316,11 +316,32 @@ public class CollectionTests
         [AssertionDiagnostic("actual.ToArray().Count().Should().Be(1{0}).And.ToString();")]
         [Implemented]
         public void CollectionShouldHaveCount_CountShouldBe1_TestAnalyzer(string assertion) => VerifyCSharpDiagnosticCodeBlock(assertion, DiagnosticMetadata.CollectionShouldContainSingle_CountShouldBe1);
-
+        
         [DataTestMethod]
-        [AssertionDiagnostic("actual.ToArray().Length.Should().Be(1{0}).And.ToString();")]
+        [AssertionDiagnostic("(array.Count() + 1).Should().Be(0{0}).And.ToString();")]
+        [AssertionDiagnostic("(array.Count() + 1).Should().Be(1{0}).And.ToString();")]
+        [AssertionDiagnostic("(array.Count() + 1).Should().Be(expectedSize{0}).And.ToString();")]
+        [AssertionDiagnostic("(list.Count + 1).Should().Be(0{0}).And.ToString();")]
+        [AssertionDiagnostic("(list.Count + 1).Should().Be(1{0}).And.ToString();")]
+        [AssertionDiagnostic("(list.Count + 1).Should().Be(expectedSize{0}).And.ToString();")]
         [Implemented]
-        public void CollectionShouldHaveCount_LengthShouldBe_TestAnalyzer(string assertion) => VerifyCSharpDiagnosticCodeBlock(assertion, DiagnosticMetadata.CollectionShouldHaveCount_LengthShouldBe);
+        public void CollectionShouldHaveCount_CountShouldBe_TestNoAnalyzer(string assertion) => DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(new StringBuilder()
+            .AppendLine("using System;")
+            .AppendLine("using System.Collections.Generic;")
+            .AppendLine("using System.Linq;")
+            .AppendLine("using FluentAssertions;")
+            .AppendLine("using FluentAssertions.Extensions;")
+            .AppendLine("namespace TestNamespace")
+            .AppendLine("{")
+            .AppendLine("    public class TestClass")
+            .AppendLine("    {")
+            .AppendLine("        public void TestMethod(string[] array, List<string> list, int expectedSize)")
+            .AppendLine("       {")
+            .AppendLine(assertion)
+            .AppendLine("       }")
+            .AppendLine("    }")
+            .AppendLine("}")
+            .ToString());
 
         [DataTestMethod]
         [AssertionDiagnostic(@"var array = new string[0, 0]; array.Length.Should().Be(0{0});")]
@@ -330,6 +351,7 @@ public class CollectionTests
         [AssertionDiagnostic(@"var array = new string[2, 2]; array.Length.Should().Be(0{0});")]
         [AssertionDiagnostic(@"var array = new string[3, 3, 3]; array.Length.Should().Be(0{0});")]
         [AssertionDiagnostic(@"int[] array1 = [1, 2, 3]; int[] array2 = [4, 5, 6]; int[] both = [..array1, ..array2]; (array1.Length + array2.Length).Should().Be(both.Length{0});")]
+        [AssertionDiagnostic("(actual.Count() + 1).Should().Be(1{0}).And.ToString();")]
         [Implemented(Reason = "https://github.com/fluentassertions/fluentassertions.analyzers/issues/309")]
         public void CollectionShouldHaveCount_LengthShouldBe_TestNoAnalyzer(string assertion) => DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(new StringBuilder()
             .AppendLine("using System;")