### Question:
ZipkinKeys { @Nullable public static Boolean sampledToBoolean(@Nullable String sampled) { return sampled == null ? null : DO_SAMPLE_VALUE.equals(sampled); } private  ZipkinKeys(); @Nullable static String sampledToString(@Nullable Boolean sampled); @Nullable static Boolean sampledToBoolean(@Nullable String sampled); static final String TRACE_ID; static final String SPAN_ID; static final String PARENT_SPAN_ID; static final String SAMPLED; static final String FLAGS; static final String DO_SAMPLE_VALUE; static final String DO_NOT_SAMPLE_VALUE; }### Answer:
@Test public void sampledToBoolean_WhenSampledIsNull_ShouldReturnNull() { assertEquals(null, ZipkinKeys.sampledToBoolean(null)); }
@Test public void sampledToBoolean_WhenSampledIsQuoted1_ShouldReturnTrue() { assertEquals(true, ZipkinKeys.sampledToBoolean("1")); }
@Test public void sampledToBoolean_WhenSampledIsQuoted0_ShouldReturnFalse() { assertEquals(false, ZipkinKeys.sampledToBoolean("0")); }