JToken.Should().BeEquivalentTo(differentJToken) returns exception

[jakubozga]

Hello,

Lately I found that if you have 2 different JTokens and call Should().BeEquivalentTo(...) you will get:
"System.FormatException: Input string was not in a correct format." instead of error message.

My guess is that this exception is caused because code is trying to call string.Format(JToken). JToken contains characters like { and } which should be escaped to {{ and }}

[dennisdoomen]

Was that BeEquivalentTo(...) provided by the FluentAssertions.Json package or the core library?

[lancerdima]

Hi,

Decided to try out your library, and hit the same issue reported by @jakubozga .
In my case:

• Library is used in netcoreapp2.0 test project
• I made sure BeEquivalentTo(...) operation is provided by FluentAssertions.Json package, JTokenAssertions class
• I am comparing two JTokens extracted from HttpRequestMessage StringContents

Stack Trace:

at System.Text.StringBuilder.FormatError()
at System.Text.StringBuilder.AppendFormatHelper(IFormatProvider provider, String format, ParamsArray args)
at System.String.FormatHelper(IFormatProvider provider, String format, ParamsArray args)
at System.String.Format(String format, Object[] args)
at FluentAssertions.Execution.MessageBuilder.FormatArgumentPlaceholders(String failureMessage, Object[] failureArgs)
at FluentAssertions.Execution.MessageBuilder.Build(String message, Object[] messageArgs, String reason, ContextDataItems contextData)
at FluentAssertions.Execution.AssertionScope.FailWith(String message, Object[] args)
at FluentAssertions.Json.JTokenAssertions.BeEquivalentTo(JToken expected, String because, Object[] becauseArgs)

Could it be that your MessageBuilder class in the original FluentAssertions app is not handling well messages without placeholders?
JSON's BeEquivalentTo is the only extension method that use FailWith message without placeholders.

[dennisdoomen]

Could it be that your MessageBuilder class in the original FluentAssertions app is not handling well messages without placeholders?

Yes, there was a problem in 4.19.3. See https://github.com/fluentassertions/fluentassertions/releases/tag/4.19.3

[lancerdima]

Using versions:
FluentAssertions - v4.19.4
FluentAssertions.Json - v4.20.0

Issue seems to be away with pre-release 5.0.0-beta0002 and 5.0.0-beta0003.

[dennisdoomen]

Hmm, I found the fix. Unfortunately, I can't resolve this issue on 4.x. You'll have to wait for 5.0.

[304NotModified]

@dennisdoomen Guess this could be closed? (V6 is released)

[dennisdoomen]

Not sure. Completely lost track of this one.