NullReferenceException in BeEquivalentTo() usage with "Using" and "When" EquivalencyAssertationOptions

“When” usage throws NullReferenceException after “Using” EquivalencyAssertionOptions

Test objects have the same type and it has CreatedDate, UpdatedDate properties.

Test Code:

input.Should().BeEquivalentTo(result, options => options
    .Using<DateTime>(context => context.Subject.Should().BeCloseTo(context.Expectation, 1000))
    .When(info => info.SelectedMemberPath.EndsWith("Date")));

Actual behavior:

Result1 StackTrace:	
at FluentAssertions.Equivalency.AssertionContext`1.CreateFromEquivalencyValidationContext(IEquivalencyValidationContext context) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\AssertionContext.cs:line 29
   at FluentAssertions.Equivalency.AssertionRule`1.AssertEquality(IEquivalencyValidationContext context) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\AssertionRule.cs:line 57
   at FluentAssertions.Equivalency.AssertionRuleEquivalencyStepAdapter.Handle(IEquivalencyValidationContext context, IEquivalencyValidator parent, IEquivalencyAssertionOptions config) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\AssertionRuleEquivalencyStepAdapter.cs:line 22
   at FluentAssertions.Equivalency.RunAllUserStepsEquivalencyStep.Handle(IEquivalencyValidationContext context, IEquivalencyValidator parent, IEquivalencyAssertionOptions config) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\RunAllUserStepsEquivalencyStep.cs:line 21
   at FluentAssertions.Equivalency.EquivalencyValidator.RunStepsUntilEquivalencyIsProven(IEquivalencyValidationContext context) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\EquivalencyValidator.cs:line 119
   at FluentAssertions.Equivalency.EquivalencyValidator.AssertEqualityUsing(IEquivalencyValidationContext context) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\EquivalencyValidator.cs:line 54
   at FluentAssertions.Equivalency.StructuralEqualityEquivalencyStep.Handle(IEquivalencyValidationContext context, IEquivalencyValidator parent, IEquivalencyAssertionOptions config) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\StructuralEqualityEquivalencyStep.cs:line 46
   at FluentAssertions.Equivalency.EquivalencyValidator.RunStepsUntilEquivalencyIsProven(IEquivalencyValidationContext context) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\EquivalencyValidator.cs:line 119
   at FluentAssertions.Equivalency.EquivalencyValidator.AssertEqualityUsing(IEquivalencyValidationContext context) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\EquivalencyValidator.cs:line 54
   at FluentAssertions.Equivalency.EquivalencyValidator.AssertEquality(EquivalencyValidationContext context) in C:\Workspaces\fluentassertions\src\FluentAssertions\Equivalency\EquivalencyValidator.cs:line 37
   at FluentAssertions.Primitives.ObjectAssertions.BeEquivalentTo[TExpectation](TExpectation expectation, Func`2 config, String because, Object[] becauseArgs) in C:\Workspaces\fluentassertions\src\FluentAssertions\Primitives\ObjectAssertions.cs:line 123

Result1 Message:	System.NullReferenceException : Object reference not set to an instance of an object.
Result1 StandardOutput:
Result1 StandardError:

Versions

FluentAssertions V5.7.0 .NET framework 4.6.1

Additional Information

Test adapted from “Equivalency Comparison Behavior” of https://fluentassertions.com/objectgraphs/

[dennisdoomen]

Maybe we should change that property to never return null and return an empty string instead.

[jnyrup]

By looking at the provided stack trace and the fact that the property types sounds to be DateTime? this is caused by #799. SelectedMemberPath is not null, it’s SelectedMemberInfo that can be null.