Chained assertions

There are many different ways to write AssertJ assertions. Having many assertions on the same object can decrease the readability. Chained assertions allow you to group multiple assertions on the same object into a single statement, making it much easier to read.

Limited expressiveness

JUnit 3, 4, 5 and 6 only provides basic assertions like assertTrue, assertFalse, assertEquals, and assertNotNull. This makes tests verbose and harder to understand, especially when they fail.

Before
After

ChainedAssertJTest.java
import java.util.List;

class ChainedAssertJTest {

    @Test
    void bundle() {
        List<Book> books = new Bundle().getBooks();

        assertThat(books).isNotNull();
        assertThat(books.size()).isEqualTo(3);
        assertThat(books).contains(new Book("Effective Java", "Joshua Bloch", 2001));
        assertThat(books).contains(new Book("Java Concurrency in Practice", "Brian Goetz", 2006));
        assertThat(books).contains(new Book("Clean Code", "Robert C. Martin", 2008));
        assertThat(books).doesNotContain(new Book("Java 8 in Action", "Raoul-Gabriel Urma", 2014));
    }
}

warning

The long list of assertions makes the test longer and harder to read.

ChainedAssertJTest.java
import org.junit.jupiter.api.Test;

import java.util.List;

import static org.assertj.core.api.Assertions.assertThat;

class ChainedAssertJTest {

    @Test
    void bundle() {
        List<Book> books = new Bundle().getBooks();

        assertThat(books)
                .hasSize(3)
                .contains(
                        new Book("Effective Java", "Joshua Bloch", 2001),
                        new Book("Java Concurrency in Practice", "Brian Goetz", 2006),
                        new Book("Clean Code", "Robert C. Martin", 2008))
                .doesNotContain(new Book("Java 8 in Action", "Raoul-Gabriel Urma", 2014));
    }
}

tip

Using chained assertions makes the test more fluent and easier to read.

Limited expressiveness​

Limited expressiveness