HaveElementWithValue?

[weitzhandler]

Hi,

I wish there was a way to assert a JObject contains an element with a value as specified.

// arrange
...
var expectedTokenKey = "token";
var expectedTokenValue = "1234";

// act
JObject json = await ...GetJsonAsync();

// assert
json.Should().HaveElementWithValue(expectedTokenKey, expectedTokenValue);

Is there another better way for that I'm unaware of?

[dennisdoomen]

No, but we do accept contributions ;-)

[jnyrup]

In the FluentAssertions core library I can only think of
GenericDictionaryAssertions.Contain(TKey key, TValue value) that does a similar combined assertion.

dictionary.Should().Contain(1, "One");

which could also be written as

dictionary.Should().ContainKey(1)
    .WhichValue.Should().Be("One");

In FluentAssertions.Json the proposed HaveElementAndValue(string expectedElement, string expectedValue)

var subject = JToken.Parse("{ 'id': 42 }");

subject.Should().HaveElementAndValue("id", "42");

can also be written as either

var subject = JToken.Parse("{ 'id': 42 }");

subject.Should().HaveElement("id")
    .Which.Should().HaveValue("42");

or

var subject = JToken.Parse("{ 'id': 42 }");

subject.Should().HaveElement("id")
    .Which.Value<string>().Should().Be("42");

Using the existing Which pattern has two benefits:

• has no implicit assumptions that the Value of the id element is convertible to string
• the same code pattern can be used for other expectations than string.

var subject = JToken.Parse("{ 'id': [42] }");

subject.Should().HaveElement("id")
    .Which.Values<int>().Should().ContainSingle()
        .Which.Should().Be(42);

[weitzhandler]

Not only do I like it, but I wasn't even aware of the Which operator, which I was so anxiously looking for 😳

Thank you 💐

[weitzhandler]

Related: fluentassertions/fluentassertions#1355.

[dennisdoomen]

But does that mean we still see value in #39?

[jnyrup]

I haven't really used FA.Json that much, but I'm not seeing cases for HaveElementAndValue that aren't already covered by the existing API.

[weitzhandler]

The use case I encountered is just like you described with the dictionary value.
I get json from HTTP API server. I want to verify the json contains a specified key and value.

[dennisdoomen]

But would subject.Should().HaveElement("id").Which.Value<string>().Should().Be("42"); work for you?

[weitzhandler]

It actually would. A syntax sugar would be nice tho. Like in dictionary, as Jonas mentioned.

[jnyrup]

I haven't dug into the history of Contain(TKey, TValue), so I'm possibly missing some historical context, but I'm not that big fan of it, as it:

• tries to assert multiple things at once, and
• can be accomplished using the WhichValue

To be clear, the existence of Contain(TKey, TValue) (in my opinion) is not the right argument to use to justify the addition of HaveElementAndValue.

[dennisdoomen]

But I don't mind it either. Having a useful shortcut is fine by me.

[weitzhandler]

But I don't mind it either. Having a useful shortcut is fine by me.

Then we're left with the naming to be decided. Let's continue this conversation in #40.

[dennisdoomen]

The naming is fine by me.

[jnyrup]

I'm a bit confused whether we're agreeing on HaveElementWithValue or HaveElementAndValue?

[dennisdoomen]

I think there's two discussions:

1. Whether or not to add this API at all.
2. What the name should be.

I know that we can accomplish the same with a combination of HaveElement and Which, but I don't mind adding this new member. I would prefer to name it HaveElementWithValue.

[jnyrup]

After a nights sleep, I'm fine adding it.
I agree that HaveElementWithValue is preferable to HaveElementAndValue.

Regarding the method signature, I'm looking at https://en.wikipedia.org/wiki/JSON#Data_types_and_syntax to get a picture of possible scenarios.

• Should it be generic HaveElementWithValue<T>(string expectedElement, T expectedValue)?
  • That won't work for Array type, as those should be extracted using Values<T> instead of Value<T>
• Should we have bool, double, string overloads
• Should it be able to handle Object

[dennisdoomen]

Json is text only, so why don't we stick to a string and a Jtoken overload?

[weitzhandler]

• Should it be generic HaveElementWithValue<T>(string expectedElement, T expectedValue)?

I like this.

Json is text only, so why don't we stick to a string and a Jtoken overload?

Eventho JSON is text only, 5 isn't recognized as "5". Similarly null != "null", in the JSON.