Test assertions using null comparison can be simplified

Metadata

ID: java-best-practices/simplify-test-assertions-null

Language: Java

Severity: Notice

Category: Best Practices

Description

Test assertions can be made more concise through the use of a more specialized assertion method.

In this rule, we check for null comparisons in assertTrue or assertFalse methods and suggest replacing with either an assertNull or assertNonNull method.

This enhances the error message clarity and improves the overall readability of the assertion for other developers.

Non-Compliant Code Examples

import org.junit.Test;
import static org.junit.Assert.*;

class Foo {
    Object a,b;
    @Test
    void testFoo() {
        assertTrue(a == null); // could be assertNull(a);
        assertTrue(a != null); // could be assertNotNull(a);

        assertFalse(a == null); // could be assertNotNull(a);
        assertFalse(a != null); // could be assertNull(a);
    }
}

Compliant Code Examples

import org.junit.Test;
import static org.junit.Assert.*;

class Foo {
    Object a,b;
    @Test
    void testFoo() {
        assertNull(a);
        assertNotNull(a);

        assertNotNull(a);
        assertNull(a);
    }
}