@Test void oneMeansKeepAllTraces() {
    CollectorSampler sampler = CollectorSampler.create(1.0f);

    assertThat(lotsOfSpans().filter(s -> sampler.isSampled(s.traceId(), false)))
        .hasSize(LOTS_OF_SPANS.length);
  }
The collector needs to apply the same decision to incremental updates in a trace.
zipkin-collector/core/src/test/java/zipkin2/collector/CollectorSamplerTest.java