@Test void rateCantBeNegative() {
    Throwable exception = assertThrows(IllegalArgumentException.class, () -> CollectorSampler.create(-1.0f));
    assertThat(exception.getMessage()).contains("rate should be between 0 and 1: was -1.0");
  }
The collector needs to apply the same decision to incremental updates in a trace.
zipkin-collector/core/src/test/java/zipkin2/collector/CollectorSamplerTest.java