Add option to generate chained assertions

[MichaelBitard]

Enhancement

Use case:

• You have an object "objectA" of type ObjectA which contains (among other fields) a field objectB of type ObjectB
• To assert it, I do

assertThat(objectA).hasFieldOfObjectA("field");
assertThat(objectA.objectB).hasFieldOfObjectB("fieldOfObjectB");

• I'd like to be able to assert like this:

assertThat(objectA)
  .hasFieldOfObjectA("field")
  .withObjectB()
    .hasFieldOfObjectB("fieldOfObjectB");

I already do that manually, but I think it could be useful to be able to add this behavior automatically.

What do you think?

[joel-costigliola]

I agree on the idea, I would just use getB() to navigate to the B's assertions.

[yoorick]

I would rather prefer to see it as has<FieldName>Satisfying(Consumer/Condition) pair of methods. Just like hasValueSatisfying for Optional or satisfies for list elements or other similar asserts. This way you can continue to fluently verify other complex fields of objectA. With getB()/withObjectB() approach you have no way to fluently return back to objectA assertions.

[yoorick]

Something like this:

assertThat(objectA)
    .hasFieldOfObjectA("field")
    .hasObjectBSatisfying(
        objectB -> assertThat(objectB)
            .hasFieldB1("value1")
            .hasFieldB2("value2")
    )
    .hasObjectCSatisfying(
        objectC -> assertThat(objectC)
            .hasFieldC1("otherValue1")
            .hasFieldC2(1234)
            .hasFieldC3("otherValue3")
    )
    // ...