### Question:
TracerShim extends BaseShimObject implements Tracer { @SuppressWarnings("ReturnMissingNullable") @Override public <C> SpanContext extract(Format<C> format, C carrier) { try { if (format == Format.Builtin.TEXT_MAP || format == Format.Builtin.TEXT_MAP_EXTRACT || format == Format.Builtin.HTTP_HEADERS) { return propagation.extractTextMap((TextMapExtract) carrier); } } catch (Exception e) { logger.log( Level.INFO, "Exception caught while extracting span context; returning null. " + "Exception: [{0}] Message: [{1}]", new String[] {e.getClass().getName(), e.getMessage()}); } return null; } TracerShim(TelemetryInfo telemetryInfo); @Override ScopeManager scopeManager(); @Override Span activeSpan(); @Override Scope activateSpan(Span span); @Override SpanBuilder buildSpan(String operationName); @Override void inject(SpanContext context, Format<C> format, C carrier); @SuppressWarnings("ReturnMissingNullable") @Override SpanContext extract(Format<C> format, C carrier); @Override void close();  }### Answer:
@Test void extract_nullContext() { SpanContext result = tracerShim.extract(Format.Builtin.TEXT_MAP, new TextMapAdapter(Collections.emptyMap())); assertNull(result); }