2.5. Assumptions

JUnit Jupiter comes with a subset of the assumption methods that JUnit 4 provides and adds a few that lend themselves well to being used with Java 8 lambda expressions and method references. All JUnit Jupiter assumptions are static methods in the [org.junit.jupiter.api.Assumptions](https://junit.org/junit5/docs/current/api/org.junit.jupiter.api/org/junit/jupiter/api/Assumptions.html) class.

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assumptions.assumeTrue;
import static org.junit.jupiter.api.Assumptions.assumingThat;
import example.util.Calculator;
import org.junit.jupiter.api.Test;
class AssumptionsDemo {
    private final Calculator calculator = new Calculator();
    @Test
    void testOnlyOnCiServer() {
        assumeTrue("CI".equals(System.getenv("ENV")));
        // remainder of test
    }
    @Test
    void testOnlyOnDeveloperWorkstation() {
        assumeTrue("DEV".equals(System.getenv("ENV")),
            () -> "Aborting test: not on developer workstation");
        // remainder of test
    }
    @Test
    void testInAllEnvironments() {
        assumingThat("CI".equals(System.getenv("ENV")),
            () -> {
                // perform these assertions only on the CI server
                assertEquals(2, calculator.divide(4, 2));
            });
        // perform these assertions in all environments
        assertEquals(42, calculator.multiply(6, 7));
    }
}