Move DD code into its own directory (#6)

reference/tests/utils/tracer.py

@@ -0,0 +1,77 @@
+from ddtrace.encoding import JSONEncoder, MsgpackEncoder
+from ddtrace.internal.writer import AgentWriter
+from ddtrace.tracer import Tracer
+
+
+class DummyWriter(AgentWriter):
+    """DummyWriter is a small fake writer used for tests. not thread-safe."""
+
+    def __init__(self, *args, **kwargs):
+        # original call
+        super(DummyWriter, self).__init__(*args, **kwargs)
+
+        # dummy components
+        self.spans = []
+        self.traces = []
+        self.services = {}
+        self.json_encoder = JSONEncoder()
+        self.msgpack_encoder = MsgpackEncoder()
+
+    def write(self, spans=None, services=None):
+        if spans:
+            # the traces encoding expect a list of traces so we
+            # put spans in a list like we do in the real execution path
+            # with both encoders
+            trace = [spans]
+            self.json_encoder.encode_traces(trace)
+            self.msgpack_encoder.encode_traces(trace)
+            self.spans += spans
+            self.traces += trace
+
+        if services:
+            self.json_encoder.encode_services(services)
+            self.msgpack_encoder.encode_services(services)
+            self.services.update(services)
+
+    def pop(self):
+        # dummy method
+        s = self.spans
+        self.spans = []
+        return s
+
+    def pop_traces(self):
+        # dummy method
+        traces = self.traces
+        self.traces = []
+        return traces
+
+    def pop_services(self):
+        # dummy method
+
+        # Setting service info has been deprecated, we want to make sure nothing ever gets written here
+        assert self.services == {}
+        s = self.services
+        self.services = {}
+        return s
+
+
+class DummyTracer(Tracer):
+    """
+    DummyTracer is a tracer which uses the DummyWriter by default
+    """
+    def __init__(self):
+        super(DummyTracer, self).__init__()
+        self._update_writer()
+
+    def _update_writer(self):
+        self.writer = DummyWriter(
+            hostname=self.writer.api.hostname,
+            port=self.writer.api.port,
+            filters=self.writer._filters,
+            priority_sampler=self.writer._priority_sampler,
+        )
+
+    def configure(self, *args, **kwargs):
+        super(DummyTracer, self).configure(*args, **kwargs)
+        # `.configure()` may reset the writer
+        self._update_writer()