diff --git a/src/Cnpj.cs b/src/Cnpj.cs
index a5f45bf..283f825 100644
--- a/src/Cnpj.cs
+++ b/src/Cnpj.cs
@@ -142,7 +142,7 @@ public static Cnpj Parse(string value)
     /// contains a valid Cnpj. If the method returns false, result equals Empty.
     /// </param>
     /// <returns> true if the parse operation was successful; otherwise, false.</returns>
-    public static bool TryParse(string value, out Cnpj result)
+    public static bool TryParse(string? value, out Cnpj result)
     {
         var normalized = Format(value);
         if (!Validate(normalized))
diff --git a/src/Cpf.cs b/src/Cpf.cs
index 2b33258..701dd2b 100644
--- a/src/Cpf.cs
+++ b/src/Cpf.cs
@@ -132,7 +132,7 @@ public static Cpf Parse(string value)
     /// contains a valid Cpf. If the method returns false, result equals Empty.
     /// </param>
     /// <returns> true if the parse operation was successful; otherwise, false.</returns>
-    public static bool TryParse(string value, out Cpf result)
+    public static bool TryParse(string? value, out Cpf result)
     {
         var normalized = Format(value, withMask: false);
         if (!Validate(normalized))
diff --git a/src/CpfCnpj.cs b/src/CpfCnpj.cs
index f13ea89..4e0b55e 100644
--- a/src/CpfCnpj.cs
+++ b/src/CpfCnpj.cs
@@ -170,7 +170,7 @@ public static CpfCnpj Parse(string value)
     /// contains a valid CpfCnpj. If the method returns false, result equals Empty.
     /// </param>
     /// <returns> true if the parse operation was successful; otherwise, false.</returns>
-    public static bool TryParse(string value, out CpfCnpj result)
+    public static bool TryParse(string? value, out CpfCnpj result)
     {
         var type = Validate(value);
         if (type is null)
diff --git a/tests/BrazilModels.Tests/CnpjTests.cs b/tests/BrazilModels.Tests/CnpjTests.cs
index d837949..f496c1a 100644
--- a/tests/BrazilModels.Tests/CnpjTests.cs
+++ b/tests/BrazilModels.Tests/CnpjTests.cs
@@ -3,6 +3,7 @@
 
 namespace BrazilModels.Tests;
 
+[TestFixture]
 public class CnpjTests
 {
     [Test]
@@ -49,7 +50,8 @@ public void ShouldCompareAsString(ValidCnpj first, ValidCnpj second)
     {
         var cnpj1 = new Cnpj(first);
         var cnpj2 = new Cnpj(second);
-        var strCompare = string.Compare(first.Cleared, second.Cleared, StringComparison.OrdinalIgnoreCase);
+        var strCompare = string.Compare(first.Cleared, second.Cleared,
+            StringComparison.OrdinalIgnoreCase);
         cnpj1.CompareTo(cnpj2).Should().Be(strCompare);
     }
 
@@ -187,12 +189,19 @@ public void ShouldCreateUnformattedCnpj(CleanCnpj input)
         }
 
         [PropertyTest]
-        public void ShouldThrowInvalidFormattedCnpj(InvalidCnpj input)
+        public void ShouldReturnFalseForInvalidFormattedCnpj(InvalidCnpj input)
         {
             Cnpj.TryParse(input.Value, out var cnpj).Should().BeFalse();
             cnpj.Value.Should().Be(Cnpj.Empty);
         }
 
+        [Test]
+        public void ShouldReturnFalseForNullString()
+        {
+            Cnpj.TryParse(null, out var cnpj).Should().BeFalse();
+            cnpj.Value.Should().Be(Cnpj.Empty);
+        }
+
         [PropertyTest]
         public void ShouldThrowInvalidUnformattedCnpj(InvalidCnpj input)
         {
diff --git a/tests/BrazilModels.Tests/TaxIdTests.cs b/tests/BrazilModels.Tests/CpfCnpjTests.cs
similarity index 95%
rename from tests/BrazilModels.Tests/TaxIdTests.cs
rename to tests/BrazilModels.Tests/CpfCnpjTests.cs
index ea8fb74..717dbca 100644
--- a/tests/BrazilModels.Tests/TaxIdTests.cs
+++ b/tests/BrazilModels.Tests/CpfCnpjTests.cs
@@ -1,6 +1,7 @@
 namespace BrazilModels.Tests;
 
-public class TaxIdTests
+[TestFixture]
+public class CpfCnpjTests
 {
     [Test]
     public void ShouldHaveEmptyFormattedTaxId() =>
@@ -14,7 +15,7 @@ public void ShouldHaveEmptyTaxId() =>
     public void NewTaxIdShouldBeEmpty() =>
         new CpfCnpj().Should().Be(CpfCnpj.Empty);
 
-    public class TaxIdCnpjTests
+    public class CnpjTests
     {
         [PropertyTest]
         public void ShouldHaveCnpjType(ValidCnpj cnpj) =>
@@ -52,7 +53,8 @@ public void ShouldCompareAsString(ValidCnpj first, ValidCnpj second)
         {
             var cnpj1 = new CpfCnpj(first);
             var cnpj2 = new CpfCnpj(second);
-            var strCompare = string.Compare(first.Cleared, second.Cleared, StringComparison.OrdinalIgnoreCase);
+            var strCompare = string.Compare(first.Cleared, second.Cleared,
+                StringComparison.OrdinalIgnoreCase);
             cnpj1.CompareTo(cnpj2).Should().Be(strCompare);
         }
 
@@ -167,12 +169,19 @@ public void ShouldCreateUnformattedTaxId(CleanCnpj input)
             }
 
             [PropertyTest]
-            public void ShouldThrowInvalidFormattedTaxId(InvalidCnpj input)
+            public void ShouldReturnFalseForInvalidFormattedTaxId(InvalidCnpj input)
             {
                 CpfCnpj.TryParse(input.Value, out var cnpj).Should().BeFalse();
                 cnpj.Value.Should().Be(CpfCnpj.Empty);
             }
 
+            [Test]
+            public void ShouldReturnFalseForNullString()
+            {
+                CpfCnpj.TryParse(null, out var cnpj).Should().BeFalse();
+                cnpj.Value.Should().Be(CpfCnpj.Empty);
+            }
+
             [PropertyTest]
             public void ShouldThrowInvalidUnformattedTaxId(InvalidCnpj input)
             {
@@ -182,9 +191,8 @@ public void ShouldThrowInvalidUnformattedTaxId(InvalidCnpj input)
         }
     }
 
-    public class TaxIdCpfTests
+    public class CpfTests
     {
-
         [PropertyTest]
         public void ShouldHaveCnpjType(ValidCpf cpf) =>
             new CpfCnpj(cpf).Type.Should().Be(DocumentType.CPF);
@@ -221,7 +229,8 @@ public void ShouldCompareAsString(ValidCpf first, ValidCpf second)
         {
             var cpf1 = new CpfCnpj(first);
             var cpf2 = new CpfCnpj(second);
-            var strCompare = string.Compare(first.Cleared, second.Cleared, StringComparison.OrdinalIgnoreCase);
+            var strCompare = string.Compare(first.Cleared, second.Cleared,
+                StringComparison.OrdinalIgnoreCase);
             cpf1.CompareTo(cpf2).Should().Be(strCompare);
         }
 
diff --git a/tests/BrazilModels.Tests/CpfTests.cs b/tests/BrazilModels.Tests/CpfTests.cs
index 19f82f8..db7989d 100644
--- a/tests/BrazilModels.Tests/CpfTests.cs
+++ b/tests/BrazilModels.Tests/CpfTests.cs
@@ -1,5 +1,6 @@
 namespace BrazilModels.Tests;
 
+[TestFixture]
 public class CpfTests
 {
     [Test]
@@ -46,7 +47,8 @@ public void ShouldCompareAsString(ValidCpf first, ValidCpf second)
     {
         var cpf1 = new Cpf(first);
         var cpf2 = new Cpf(second);
-        var strCompare = string.Compare(first.Cleared, second.Cleared, StringComparison.OrdinalIgnoreCase);
+        var strCompare = string.Compare(first.Cleared, second.Cleared,
+            StringComparison.OrdinalIgnoreCase);
         cpf1.CompareTo(cpf2).Should().Be(strCompare);
     }
 
@@ -185,12 +187,19 @@ public void ShouldCreateUnformattedCpf(CleanCpf input)
         }
 
         [PropertyTest]
-        public void ShouldThrowInvalidFormattedCpf(InvalidCpf input)
+        public void ShouldReturnFalseForInvalidFormattedCpf(InvalidCpf input)
         {
             Cpf.TryParse(input.Value, out var cpf).Should().BeFalse();
             cpf.Value.Should().Be(Cpf.Empty);
         }
 
+        [Test]
+        public void ShouldReturnFalseForNullString()
+        {
+            Cpf.TryParse(null, out var cnpj).Should().BeFalse();
+            cnpj.Value.Should().Be(Cpf.Empty);
+        }
+
         [PropertyTest]
         public void ShouldThrowInvalidUnformattedCpf(InvalidCpf input)
         {
diff --git a/tests/BrazilModels.Tests/TypeConvertersTests.cs b/tests/BrazilModels.Tests/TypeConvertersTests.cs
index 368b1c8..c0cede1 100644
--- a/tests/BrazilModels.Tests/TypeConvertersTests.cs
+++ b/tests/BrazilModels.Tests/TypeConvertersTests.cs
@@ -2,8 +2,10 @@
 using BrazilModels;
 using BrazilModels.Tests.Utils;
 
+#pragma warning disable S2187
 namespace BrazilModels.Tests;
 
+[TestFixture]
 public class TypeConverterTests : BaseTest
 {
     public class CpfTests
@@ -102,7 +104,7 @@ public void ConvertToShouldWorkString(ValidCnpj input)
         }
     }
 
-    public class TaxIdTests
+    public class CpfCnpjTests
     {
         [Test]
         public void ConverterIdValidShouldBeTrueToString()