### Question:
SpanBuilder implements Tracer.SpanBuilder { @Override public Tracer.SpanBuilder asChildOf(io.opentracing.SpanContext parent) { return addReference(CHILD_OF, parent); } SpanBuilder(String operationName, AbstractTracer tracer); @Override Tracer.SpanBuilder asChildOf(io.opentracing.SpanContext parent); @Override Tracer.SpanBuilder asChildOf(io.opentracing.Span parent); @Override Tracer.SpanBuilder addReference(String type, io.opentracing.SpanContext referredTo); @Override Tracer.SpanBuilder ignoreActiveSpan(); Tracer.SpanBuilder withTag(String key, String value); Tracer.SpanBuilder withTag(String key, boolean value); Tracer.SpanBuilder withTag(String key, Number value); Tracer.SpanBuilder withTag(io.opentracing.tag.Tag<T> tag, T value); Tracer.SpanBuilder withStartTimestamp(long microseconds); @SuppressWarnings({"WeakerAccess", "UnusedReturnValue", "SameParameterValue"}) Tracer.SpanBuilder withTraceIdAndSpanId(long traceId, long spanId); @SuppressWarnings("WeakerAccess") Iterable<Map.Entry<String, String>> baggageItems(); @Override io.opentracing.Span start();  }### Answer:
@Test public void testStart_asChildOfSpan() throws Exception { Span span = new Span(null, context, null, 0L); undertest.asChildOf(span); verifySettingsFromParent(); }
@Test public void testStart_asChildOfSpanContext() throws Exception { undertest.asChildOf(context); verifySettingsFromParent(); }