In this part of this section is about the so-called assumptions. Assumptions allow us to only run tests if certain conditions are as expected. All JUnit Jupiter assumptions are static methods in the class Assumptions, located inside the org.junit.jupiter package. The following screenshot shows all the methods of this class:

On the one hand, the methods assumeTrue and assumeFalse can be used to skip tests whose preconditions are not met. On the other hand, the method assumingThat is used to condition the execution of a part in a test:

package io.github.bonigarcia;

import static org.junit.jupiter.api.Assertions.fail;
import static org.junit.jupiter.api.Assumptions.assumeFalse;
import static org.junit.jupiter.api.Assumptions.assumeTrue;
import static org.junit.jupiter.api.Assumptions.assumingThat;

import org.junit.jupiter.api.Test;

class AssumptionsTest {

    @Test
    void assumeTrueTest() {
        assumeTrue(false);
        fail("Test 1 failed");
    }

    @Test
    void assumeFalseTest() {
        assumeFalse(this::getTrue);
        fail("Test 2 failed");
    }

    private boolean getTrue() {
        return true;
    }

    @Test
    void assummingThatTest() {
        assumingThat(false, () -> fail("Test 3 failed"));
    }

}

Notice that in this example, the two first tests (assumeTrueTest and assumeFalseTest) are skipped since the assumptions are not met. Nevertheless, in the assummingThatTest test, only this part of the test (a lambda expression in this case) is not executed, but the whole test is not skipped: