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kotlinlang

Couldn't you just do `expectThat(data).dataAssertion()`

I don’t think so. The entire assertion is:
```fun &lt;D : Operation.Data&gt; Result&lt;ApolloResponse&lt;D&gt;, ApolloException&gt;.assertIsSuccessful(
    dataAssertion: (Assertion.Builder&lt;D&gt;.() -&gt; Unit)? = null
): D = expectThat(this)
    .and { get { isSuccess() }.isTrue() } // Result is a success
    .get { get() } // get the ApolloResponse&lt;D&gt;
    .and { get { errors }.isNull() } // ApolloResponse&lt;D&gt; does not have errors
    .get { data }.isNotNull() // ApolloResponse has data D
    .also { data -&gt; dataAssertion?.invoke(data) } // custom assertion on data D
    .subject // return the data D held by ApolloResponse```

It looks like you could replace
```    .get { data }.isNotNull() // ApolloResponse has data D
    .also { data -&gt; dataAssertion?.invoke(data) } // custom assertion on data D```
with
```    .get { data }.isNotNull().dataAssertion()```

`dataAssertion` is nullable, though. I suppose it could be non-nullable and default to always true

it might work if the signature was
```dataAssertion: (Assertion.Builder&lt;D&gt;.() -&gt; Unit) = { },```

actually this
```dataAssertion: (Assertion.Builder&lt;D&gt;.() -&gt; D) = { subject },```


```fun &lt;D : Operation.Data&gt; Result&lt;ApolloResponse&lt;D&gt;, ApolloException&gt;.assertIsSuccessful(
    dataAssertion: (Assertion.Builder&lt;D&gt;.() -&gt; Unit) = { },
): D = expectThat(this)
    .and { get { isSuccess() }.isTrue() }
    .get { get() }
    .and { get { errors }.isNull() }
    .get { data }.isNotNull()
    .and { dataAssertion() }
    .subject```
this wouldn’t require any of the callers to change