public TpcEngineBuilder setReactorCount(int reactorCount) {
        this.reactorCount = checkPositive(reactorCount, "reactorCount");
        return this;
    }
@Test
    public void test_setReactorCountWhenZero() {
        TpcEngineBuilder builder = new TpcEngineBuilder();
        assertThrows(IllegalArgumentException.class, () -> builder.setReactorCount(0));
    }