AssertJ-core is a Java library that provides a fluent interface for writing assertions. It can be installed using Maven and provides examples of how to write basic assertions like checking for expected exceptions and comparing arrays. AssertJ-core allows assertions to be written in a fluent style and is concluded to be the best assertion library for Java.

1. AssertJ-core
By Franck Benault
Created 06/06/2015
Last update 07/09/2015

2. Assertj-core introduction
● AssertJ core is a java library that provides a fluent
interface for writing assertion.

3. AssertJ plan

4. AssertJ installation
● Maven dependency
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<!-- use 3.0.0 for Java 8 projects -->
<version>2.0.0</version>
<scope>test</scope>
</dependency>

5. AssertJ is a fluent interface
● Example
String s1 = "Frodo";
assertThat(s1).startsWith("Fro")
.endsWith("do")
.isEqualToIgnoringCase("frodo");

6. AssertJ : write basic assertions
@Test(expected=ArithmeticException.class)
public void t00fail() {
int i1= 0;
int i2= 0;
@SuppressWarnings("unused")
int res = i1/i2;
fail("exception expected");
}

7. AssertJ : write basic assertions
@Test
public void t01AssertArrayEqualsTest() {
int[] ints1 = {1,3};
int[] ints2 = {1,3};
assertThat(ints1).isEqualTo(ints2);
assertThat(ints1).as("tab of int").isEqualTo(ints2);
}

8. Conclusion
● Assertj-core is the best assertion library in java

9. Around AssertJ

10. Around AssertJ