NotBeApproximately double version accepting nullable subject and expe…

…cted

Src/FluentAssertions/NumericAssertionsExtensions.cs

@@ -1088,13 +1088,53 @@ public static class NumericAssertionsExtensions
             double unexpectedValue, double precision, string because = "",
             params object[] becauseArgs)
         {
-            Execute.Assertion
-                .ForCondition(parent.Subject != null)
+            if (parent.Subject != null)
+            {
+                var nonNullableAssertions = new NumericAssertions<double>((double)parent.Subject);
+                nonNullableAssertions.NotBeApproximately(unexpectedValue, precision, because, becauseArgs);
+            }
+
+            return new AndConstraint<NullableNumericAssertions<double>>(parent);
+        }
+
+        /// <summary>
+        /// Asserts a double value does not approximate another value by a given amount.
+        /// Throws if both subject and <paramref name="unexpectedValue"/> are null.
+        /// </summary>
+        /// <param name="parent">The <see cref="NumericAssertions{T}"/> object that is being extended.</param>
+        /// <param name="unexpectedValue">
+        /// The unexpected value to compare the actual value with.
+        /// </param>
+        /// <param name="precision">
+        /// The minimum exclusive amount of which the two values should differ.
+        /// </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 <see cref="because"/>.
+        /// </param>
+        public static AndConstraint<NullableNumericAssertions<double>> NotBeApproximately(this NullableNumericAssertions<double> parent,
+            double? unexpectedValue, double precision, string because = "",
+            params object[] becauseArgs)
+        {
+            if (parent.Subject == null && unexpectedValue != null ||
+                parent.Subject != null && unexpectedValue == null)
+            {
+                return new AndConstraint<NullableNumericAssertions<double>>(parent);
+            }
+
+            bool succeeded = Execute.Assertion
+                .ForCondition(parent.Subject != null && unexpectedValue != null)
                 .BecauseOf(because, becauseArgs)
-                .FailWith("Expected {context:value} to not approximate {0} +/- {1}{reason}, but it was <null>.", unexpectedValue, precision);
+                .FailWith("Expected {context:value} to not approximate {0} +/- {1}{reason}, but it was {2}.", unexpectedValue, precision, parent.Subject);
 
-            var nonNullableAssertions = new NumericAssertions<double>((double)parent.Subject);
-            NotBeApproximately(nonNullableAssertions, unexpectedValue, precision, because, becauseArgs);
+            if (succeeded)
+            {
+                // ReSharper disable once PossibleInvalidOperationException
+                parent.NotBeApproximately(unexpectedValue.Value, precision, because, becauseArgs);
+            }
 
             return new AndConstraint<NullableNumericAssertions<double>>(parent);
         }

Tests/Shared.Specs/NullableNumericAssertionSpecs.cs

@@ -799,8 +799,7 @@ public void When_asserting_not_approximately_and_nullable_double_has_no_value_it
             //-----------------------------------------------------------------------------------------------------------
             // Assert
             //-----------------------------------------------------------------------------------------------------------
-            act.Should().Throw<XunitException>().WithMessage(
-                "Expected value to not approximate 3.14 +/- 0.001, but it was <null>.");
+            act.Should().NotThrow();
         }
 
         [Fact]
@@ -824,6 +823,107 @@ public void When_asserting_not_approximately_and_nullable_double_is_indeed_appro
                 .WithMessage("Expected value to not approximate 3.14 +/- 0.1, but 3.14*only differed by*");
         }
 
+        [Fact]
+        public void When_asserting_not_approximately_and_nullable_double_is_not_approximating_a_nullable_value_it_should_not_throw()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            double? value = 3.1415927;
+            double? expected = 1.0;
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => value.Should().NotBeApproximately(expected, 0.1);
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.Should().NotThrow();
+        }
+
+        [Fact]
+        public void When_asserting_not_approximately_and_nullable_double_is_not_approximating_a_null_value_it_should_throw()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            double? value = 3.1415927;
+            double? expected = null;
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => value.Should().NotBeApproximately(expected, 0.1);
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.Should().NotThrow();
+        }
+
+        [Fact]
+        public void When_asserting_not_approximately_and_null_double_is_not_approximating_a_nullable_double_value_it_should_throw()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            double? value = null;
+            double? expected = 20.0;
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => value.Should().NotBeApproximately(expected, 0.1);
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.Should().NotThrow();
+        }
+
+        [Fact]
+        public void When_asserting_not_approximately_and_null_double_is_not_approximating_a_null_value_it_should_not_throw()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            double? value = null;
+            double? expected = null;
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => value.Should().NotBeApproximately(expected, 0.1);
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.Should().Throw<XunitException>()
+                .WithMessage("Expected*null*0.1*but*null*");
+        }
+
+        [Fact]
+        public void When_asserting_not_approximately_and_nullable_double_is_approximating_a_nullable_value_it_should_throw()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            double? value = 3.1415927;
+            double? expected = 3.1;
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => value.Should().NotBeApproximately(expected, 0.1F);
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.Should().Throw<XunitException>();
+        }
+
         [Fact]
         public void When_asserting_not_approximately_and_nullable_float_is_not_approximating_a_value_it_should_not_throw()
         {

Tests/Shared.Specs/NumericAssertionSpecs.cs

@@ -1888,9 +1888,7 @@ public void When_a_nullable_double_has_no_value_and_should_not_approximate_it_sh
             //-----------------------------------------------------------------------------------------------------------
             // Assert
             //-----------------------------------------------------------------------------------------------------------
-            act
-                .Should().Throw<XunitException>()
-                .WithMessage("Expected value to not approximate*3.14* +/-*0.001*, but it was <null>.");
+            act.Should().NotThrow();
         }
 
         #endregion