Google Truth and AssertJ delivered a new style of assertions, where you don’t need to remember a lot of method names and class names placed in packages of Hamcrest’s jar file.

It made possible to rely on your IDE for listing available methods, from which you can choose a desired one, instead of relying on your memory for it.

The only thing that you need to remember is the fact that the method assertThat is what you need. Once you type assertThat(yourValue), your IDE will suggest to do static import [Figure.1].

IntelliJ suggest to do static import

And then, list methods that can be imported statically from your classpath[Figure.2].

IntelliJ suggests statically importable assertThat methods

To render these images, I used the code found at [BaeldungAssertJ].

The Pain Points

Please look at the method names and their packages a bit carefully.

These are the custom supports available for the target class Dog.

PersonAssert.assertThat(com.baeldung.assertj.custom) (1)
Assertions.assertThat(com.baeldung.assertj.custom) (2)
UserSubject.assertThat(com.baeldung.assertj.custom) (3)

  1. Support for AssertJ

  2. Support for Hamcrest

  3. Support for Google Truth

For instance, the class PersonAssert is implemented as follows. This code is cited from [BaeldungAssertionTutorial] and I’ve annotated [1].

package com.baeldung.assertj.custom;

import org.assertj.core.api.AbstractAssert;

public class PersonAssert extends AbstractAssert<PersonAssert, Person> {

    public PersonAssert(Person actual) {
        super(actual, PersonAssert.class);
    }

    public static PersonAssert assertThat(Person actual) {
        return new PersonAssert(actual);
    }

    public PersonAssert hasFullName(String fullName) {
        isNotNull();
        if (!actual.getFullName().equals(fullName)) {
            failWithMessage("Expected person to have full name %s but was %s", fullName, actual.getFullName()); //(1)
        }
        return this;
    }

    public PersonAssert isAdult() {
        isNotNull();
        if (actual.getAge() < 18) {
            failWithMessage("Expected person to be adult"); //(1)
        }
        return this;
    }

    public PersonAssert hasNickname(String nickName) {
        isNotNull();
        if (!actual.getNicknames().contains(nickName)) {
            failWithMessage("Expected person to have nickname %s", nickName); //(1)
        }
        return this;
    }
}

  1. A message string that a human programmer needs to come up with.

This is the first paint point in the "fluent" assertion style in these days, I’d point out. As annotated, you need to come up with a good message for each verification method. Another pain is the fact itself that we need to create a custom support class for your class every time.

Next Post: Yet another pain point (or others?)

This time, I mentioned a couple of pain points of the modern fluent assertion style, but they are not all. In the next post, I will discuss yet another pain point, or two.

References

1. So, is Dog a person? Please don’t blame me.