AssertJ casting an extracted field to a Map

Question

I have a Message object with MessageHeaders field. The MessageHeaders class implements a Map<String, Object>. I want to assert that I have specific headers set. I'm having trouble getting the MapAssert methods to come up.

Here's what I want to accomplish:

assertThat(actual)
  .extracting(Message::getHeaders) // This returns AbstractObjectAssert though
  .containsKeys("some key");  // Not available

Here's the Message and MessageHeaders class to be clear:

public class Message {
  private MessageHeaders headers;
  // getter
}


public class MessageHeaders implements Map<String, Object>, Serializable {
  // methods
}

jota3 · Accepted Answer · 2020-05-12T13:23:51.503

20

In order to use MapAssert you need to extract directly the MessageHeaders field and cast the extraction with asInstanceOf :

assertThat(actual)
.extracting("headers")
.asInstanceOf(InstanceOfAssertFactories.MAP)
.containsKey("some key");

edited May 12 '20 at 13:23

answered Aug 21 '19 at 21:13

jota3

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`asInstanceOf()` was introduced in `AssertJ Core 3.13.0 Release`. I will have to update. – George Aug 23 '19 at 18:55
It changed to isInstanceOf() – Badr Kacimi Feb 16 '23 at 17:38

Stefano Cordio · Answer 2 · 2019-11-02T20:46:55.660

7

AssertJ Core 3.14.0 provides a new extracting() to support direct casting, so you can write:

assertThat(actual)
  .extracting(Message::getHeaders, as(InstanceOfAssertFactories.MAP))
  .containsKey("some key");

Note that as() is an optional syntax sugar to improve readability.

edited Nov 02 '19 at 20:46

answered Aug 29 '19 at 05:00

Stefano Cordio

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score 0 · Answer 3 · answered Aug 21 '19 at 20:02

0

The solution / workaround I came up with was to assert the map itself instead of using extracting.

assertThat(actual.getHeaders())
  .containsKey("some key");

answered Aug 21 '19 at 20:02

George

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AssertJ casting an extracted field to a Map

3 Answers3