Don't override the return type in buildSpan().

[mmimica]

This makes it possible to override buildSpan(String op) of MockTracer and return another impl of Tracer.SpanBuilder.
A use-case for this would be, for example, to supply an instance of SpanBuilder that delegates to original MockTracer.SpanBuilder, but also performs additional logging.

[coveralls]

Coverage remained the same at 76.586% when pulling 6bc1d8a on mmimica:master into a8557d7 on opentracing:master.

[whiskeysierra]

The proper way of doing this would be composition, not inheritance. You can take a look at https://github.com/zalando/opentracing-toolbox/tree/master/opentracing-proxy to see an example.

[mmimica]

The proper way of doing this would be composition, not inheritance.

Indeed.

[yurishkuro]

if you extend MockTracer.SpanBuilder, then you do not need this change.

[mmimica]

if you extend MockTracer.SpanBuilder, then you do not need this change.

My extension to SpanBuilder is generic and has nothing to do with mocks, so I'm not going do that.

[yurishkuro]

if you're using MockTracer, you should be extending its subcomponents.

You're proposing a breaking change.