FooTest.java

public class FooTest {
    static class WithValue<T> {
        final T v;
        WithValue(T v) {
            this.v = v;
        }

        void doTest(Consumer<T> f) {
            f.accept(v);
        }
    }

    <T> WithValue<T> with(T v) {
        return new WithValue(v);
    }
  
    @Test public emptyString() {
        with("").doTest(s -> assertEquals(0, s.length()));
    }
}