Use Assert.Null when validating against null

exercises/phone-number/PhoneNumberTest.cs

@@ -29,14 +29,14 @@ public void Cleans_numbers_with_multiple_spaces()
     public void Invalid_when_9_digits()
     {
         var phrase = "123456789";
-        Assert.Equal(null, PhoneNumber.Clean(phrase));
+        Assert.Null(PhoneNumber.Clean(phrase));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Invalid_when_11_digits_does_not_start_with_a_1()
     {
         var phrase = "22234567890";
-        Assert.Equal(null, PhoneNumber.Clean(phrase));
+        Assert.Null(PhoneNumber.Clean(phrase));
     }
 
     [Fact(Skip = "Remove to run test")]
@@ -57,34 +57,34 @@ public void Valid_when_11_digits_and_starting_with_1_even_with_punctuation()
     public void Invalid_when_more_than_11_digits()
     {
         var phrase = "321234567890";
-        Assert.Equal(null, PhoneNumber.Clean(phrase));
+        Assert.Null(PhoneNumber.Clean(phrase));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Invalid_with_letters()
     {
         var phrase = "123-abc-7890";
-        Assert.Equal(null, PhoneNumber.Clean(phrase));
+        Assert.Null(PhoneNumber.Clean(phrase));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Invalid_with_punctuations()
     {
         var phrase = "123-@:!-7890";
-        Assert.Equal(null, PhoneNumber.Clean(phrase));
+        Assert.Null(PhoneNumber.Clean(phrase));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Invalid_if_area_code_does_not_start_with_2_9()
     {
         var phrase = "(123) 456-7890";
-        Assert.Equal(null, PhoneNumber.Clean(phrase));
+        Assert.Null(PhoneNumber.Clean(phrase));
     }
 
     [Fact(Skip = "Remove to run test")]
     public void Invalid_if_exchange_code_does_not_start_with_2_9()
     {
         var phrase = "(223) 056-7890";
-        Assert.Equal(null, PhoneNumber.Clean(phrase));
+        Assert.Null(PhoneNumber.Clean(phrase));
     }
 }

generators/Exercise.cs

@@ -69,10 +69,19 @@ protected virtual string RenderTestMethodBody(CanonicalDataCase canonicalDataCas
         protected virtual TestMethodBody CreateTestMethodBody(CanonicalDataCase canonicalDataCase)
         {
             if (canonicalDataCase.ExceptionThrown != null)
+            {
                 return new TestMethodBodyWithExceptionCheck(canonicalDataCase, CanonicalData);
+            }
 
             if (canonicalDataCase.Expected is bool)
+            {
                 return new TestMethodBodyWithBooleanCheck(canonicalDataCase, CanonicalData);
+            }
+
+            if (canonicalDataCase.Expected is null)
+            {
+                return new TestMethodBodyWithNullCheck(canonicalDataCase, CanonicalData);
+            }
 
             return new TestMethodBodyWithEqualityCheck(canonicalDataCase, CanonicalData);
         }
@@ -86,4 +95,4 @@ protected virtual string RenderTestMethodBodyAct(TestMethodBody testMethodBody)
         protected virtual string RenderTestMethodBodyAssert(TestMethodBody testMethodBody)
             => TemplateRenderer.RenderPartial(testMethodBody.AssertTemplateName, testMethodBody.AssertTemplateParameters);
     }
-}
+}

generators/Exercises/PhoneNumber.cs

@@ -1,5 +1,4 @@
 using Generators.Input;
-using Generators.Output;
 
 namespace Generators.Exercises
 {
@@ -10,7 +9,6 @@ protected override void UpdateCanonicalData(CanonicalData canonicalData)
             foreach (var canonicalDataCase in CanonicalData.Cases)
             {
                 canonicalDataCase.UseVariablesForInput = true;
-                canonicalDataCase.Expected = canonicalDataCase.Expected ?? new UnescapedValue("null");
             }
         }
     }

generators/Output/Templates/_AssertNull.liquid

@@ -0,0 +1 @@
+Assert.Null({{ TestedValue }});

generators/Output/TestMethodBodyWithNullCheck.cs

@@ -0,0 +1,13 @@
+using Generators.Input;
+
+namespace Generators.Output
+{
+    public class TestMethodBodyWithNullCheck : TestMethodBody
+    {
+        public TestMethodBodyWithNullCheck(CanonicalDataCase canonicalDataCase, CanonicalData canonicalData) : base(canonicalDataCase, canonicalData)
+        {
+            AssertTemplateName = "AssertNull";
+            AssertTemplateParameters = new { Data.TestedValue };
+        }
+    }
+}