Let's move on to the JUnit 5 programming model. Jupiter comes with many of the assertion methods such as the ones in JUnit 4, and also adds several that can be used with Java 8 lambdas. All JUnit Jupiter assertions are static methods in the Assertions class located in org.junit.jupiter package.
The following picture shows the complete list of these methods:
The following table reviews the different types of basic assertions in Jupiter:
|
Assertion |
Description |
|
fail |
Fails a test with a given message and/or exception |
|
assertTrue |
Asserts that a supplied condition is true |
|
assertFalse |
Asserts that a supplied condition is false |
|
assertNull |
Asserts that a supplied object is null |
|
assertNotNull |
Asserts that a supplied object is not null |
|
assertEquals |
Asserts that two supplied objects are equal |
|
assertArrayEquals |
Asserts that two supplied arrays are equal |
|
assertIterableEquals |
Asserts that two iterable objects are deeply equal |
|
assertLinesMatch |
Asserts that two lists of Strings are equals |
|
assertNotEquals |
Asserts that two supplied objects are not equal |
|
assertSame |
Asserts that two objects are the same, compared with == |
|
assertNotSame |
Asserts that two objects are different, compared with != |
The following example shows a test using the assertEquals, assertTrue, and assertFalse assertion. Note that we are importing the static assertion methods at the beginning of the class in order to improve the readability of the test logic. In the example, we find the assertEquals method, in this case comparing two primitive types (it could also be used for objects). Second, the method assertTrue evaluates if a boolean expression is true. Third, the method assertFalse evaluates if a Boolean expression is false. In this case, notice that the message is created as a Lamdba expression. This way, assertion messages are lazily evaluated to avoid constructing complex messages unnecessarily:
package io.github.bonigarcia;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertTrue;
import org.junit.jupiter.api.Test;
class StandardAssertionsTest {
@Test
void standardAssertions() {
assertEquals(2, 2);
assertTrue(true,
"The optional assertion message is now the last parameter");
assertFalse(false, () -> "Really " + "expensive " + "message"
+ ".");
}
}
The following parts of this section review the advance assertions provided by Jupiter: assertAll, assertThrows, assertTimeout, and assertTimeoutPreemptively.