AssertJ - Condition

[Last Updated: Mar 3, 2026]

An AssertJ Condition<T> is a named, reusable predicate that can be passed to is(), has(), satisfies(), and collection methods like are() and have(). Conditions are useful when the same logical check is applied in multiple tests, or when you want a human-readable name for a complex predicate.

Combining Conditions

AssertJ provides combinators: allOf(c1, c2) requires all conditions to hold, anyOf(c1, c2) requires at least one to hold, and not(condition) inverts the condition.

Creating a Condition

Condition<String> uppercase = new Condition<>(s -> s.equals(s.toUpperCase()), "uppercase");
assertThat("HELLO").is(uppercase);

Example

package com.logicbig.example;

import org.junit.jupiter.api.Test;

import org.assertj.core.api.Condition;
import java.util.List;
import static org.assertj.core.api.Assertions.*;

public class ConditionExample {

    @Test
    void myTest() {
        // define reusable conditions
        Condition<String> longWord = new Condition<>(s -> s.length() > 5,
                                                     "long word");
        Condition<String> startsWithA = new Condition<>(s -> s.startsWith("A"),
                                                        "starts with A");

        assertThat("Algorithm").is(longWord);
        System.out.println("longWord condition passed");

        assertThat("Algorithm").is(startsWithA);
        System.out.println("startsWithA condition passed");

        // allOf combinator
        assertThat("Algorithm").is(allOf(longWord, startsWithA));
        System.out.println("allOf passed");

        // anyOf combinator
        assertThat("JavaProgramming").is(anyOf(longWord, startsWithA));
        System.out.println("anyOf passed");

        // collection with condition
        List<String> words = List.of("Algorithm", "Array", "Abstract");
        assertThat(words).are(startsWithA);
        System.out.println("Collection condition passed");
    }
}

Output

$ mvn clean test -Dtest=*
[INFO] Scanning for projects...
[INFO] 
[INFO] ---------------< com.logicbig.example:assertj-condition >---------------
[INFO] Building assertj-condition 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- clean:3.2.0:clean (default-clean) @ assertj-condition ---
[INFO] Deleting D:\example-projects\assertj\assertj-condition\target
[INFO] 
[INFO] --- resources:3.3.1:resources (default-resources) @ assertj-condition ---
[INFO] skip non existing resourceDirectory D:\example-projects\assertj\assertj-condition\src\main\resources
[INFO] 
[INFO] --- compiler:3.11.0:compile (default-compile) @ assertj-condition ---
[INFO] No sources to compile
[INFO] 
[INFO] --- resources:3.3.1:testResources (default-testResources) @ assertj-condition ---
[INFO] skip non existing resourceDirectory D:\example-projects\assertj\assertj-condition\src\test\resources
[INFO] 
[INFO] --- compiler:3.11.0:testCompile (default-testCompile) @ assertj-condition ---
[INFO] Changes detected - recompiling the module! :source
[INFO] Compiling 1 source file with javac [debug target 17] to target\test-classes
[INFO] 
[INFO] --- surefire:3.2.5:test (default-test) @ assertj-condition ---
[INFO] Using auto detected provider org.apache.maven.surefire.junitplatform.JUnitPlatformProvider
[WARNING] file.encoding cannot be set as system property, use <argLine>-Dfile.encoding=...</argLine> instead
[INFO] 
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running com.logicbig.example.ConditionExample
longWord condition passed
startsWithA condition passed
allOf passed
anyOf passed
Collection condition passed
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.172 s -- in com.logicbig.example.ConditionExample
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  4.234 s
[INFO] Finished at: 2026-03-03T14:22:26+08:00
[INFO] ------------------------------------------------------------------------

Conclusion

The output confirms that defined conditions correctly evaluate their predicates, and that allOf and anyOf compose them as expected. Encapsulating predicates as named Condition objects improves test readability and centralizes reusable validation logic.