Extend NullableBooleanAssertions by NotBe()

Src/FluentAssertions/Primitives/NullableBooleanAssertions.cs

@@ -118,6 +118,27 @@ public AndConstraint<TAssertions> Be(bool? expected, string because = "", params
             return new AndConstraint<TAssertions>((TAssertions)this);
         }
 
+        /// <summary>
+        /// Asserts that the value is not equal to the specified <paramref name="unexpected"/> value.
+        /// </summary>
+        /// <param name="unexpected">The unexpected value</param>
+        /// <param name="because">
+        /// A formatted phrase as is supported by <see cref="string.Format(string,object[])" /> explaining why the assertion
+        /// is needed. If the phrase does not start with the word <i>because</i>, it is prepended automatically.
+        /// </param>
+        /// <param name="becauseArgs">
+        /// Zero or more objects to format using the placeholders in <paramref name="because" />.
+        /// </param>
+        public AndConstraint<TAssertions> NotBe(bool? unexpected, string because = "", params object[] becauseArgs)
+        {
+            Execute.Assertion
+                .ForCondition(Subject != unexpected)
+                .BecauseOf(because, becauseArgs)
+                .FailWith("Expected {context:nullable boolean} not to be {0}{reason}, but found {1}.", unexpected, Subject);
+
+            return new AndConstraint<TAssertions>((TAssertions)this);
+        }
+
         /// <summary>
         /// Asserts that the value is not <c>false</c>.
         /// </summary>

Tests/Approval.Tests/ApprovedApi/FluentAssertions/net47.verified.txt

@@ -1951,6 +1951,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> Be(bool? expected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> BeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> HaveValue(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotBe(bool? unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeFalse(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeTrue(string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/net6.0.verified.txt

@@ -2008,6 +2008,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> Be(bool? expected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> BeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> HaveValue(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotBe(bool? unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeFalse(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeTrue(string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/netcoreapp2.1.verified.txt

@@ -1951,6 +1951,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> Be(bool? expected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> BeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> HaveValue(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotBe(bool? unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeFalse(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeTrue(string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/netcoreapp3.0.verified.txt

@@ -1951,6 +1951,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> Be(bool? expected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> BeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> HaveValue(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotBe(bool? unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeFalse(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeTrue(string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/netstandard2.0.verified.txt

@@ -1903,6 +1903,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> Be(bool? expected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> BeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> HaveValue(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotBe(bool? unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeFalse(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeTrue(string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/netstandard2.1.verified.txt

@@ -1951,6 +1951,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> Be(bool? expected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> BeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> HaveValue(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotBe(bool? unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeFalse(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeNull(string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotBeTrue(string because = "", params object[] becauseArgs) { }

Tests/FluentAssertions.Specs/Primitives/NullableBooleanAssertionSpecs.cs

@@ -200,6 +200,22 @@ public void When_asserting_boolean_null_value_to_be_equal_to_different_nullable_
                 .WithMessage("Expected False because we want to test the failure message, but found <null>.");
         }
 
+        [Fact]
+        public void When_asserting_boolean_null_value_not_to_be_equal_to_same_value_should_fail()
+        {
+            // Arrange
+            bool? nullableBoolean = null;
+            bool? differentNullableBoolean = null;
+
+            // Act
+            Action action = () =>
+                nullableBoolean.Should().NotBe(differentNullableBoolean, "we want to test the failure {0}", "message");
+
+            // Assert
+            action.Should().Throw<XunitException>()
+                .WithMessage("Expected nullableBoolean not to be <null> because we want to test the failure message, but found <null>.");
+        }
+
         [Fact]
         public void When_asserting_boolean_null_value_to_be_equal_to_null_it_should_succeed()
         {
@@ -215,6 +231,21 @@ public void When_asserting_boolean_null_value_to_be_equal_to_null_it_should_succ
             action.Should().NotThrow();
         }
 
+        [Fact]
+        public void When_asserting_boolean_null_value_not_to_be_equal_to_different_value_it_should_succeed()
+        {
+            // Arrange
+            bool? nullableBoolean = true;
+            bool? otherNullableBoolean = null;
+
+            // Act
+            Action action = () =>
+                nullableBoolean.Should().NotBe(otherNullableBoolean);
+
+            // Assert
+            action.Should().NotThrow();
+        }
+
         [Fact]
         public void When_asserting_true_is_not_false_it_should_succeed()
         {

docs/_pages/releases.md

@@ -13,6 +13,7 @@ sidebar:
 * Annotated `[Not]MatchRegex(string)` with `[StringSyntax("Regex")]` which IDEs can use to colorize the regular expression argument - [#1816](https://github.com/fluentassertions/fluentassertions/pull/1816)
 * Added support for .NET6 `DateOnly` struct - [#1844](https://github.com/fluentassertions/fluentassertions/pull/1844)
 * Added support for .NET6 `TimeOnly` struct - [#1848](https://github.com/fluentassertions/fluentassertions/pull/1848)
+* Added `NotBe` for nullable boolean values - [#1865](https://github.com/fluentassertions/fluentassertions/pull/1865)
 
 ### Fixes
 * `EnumAssertions.Be` did not determine the caller name - [#1835](https://github.com/fluentassertions/fluentassertions/pull/1835)