diff --git a/tests/test_tracing.py b/tests/test_tracing.py
new file mode 100644
index 0000000..62171b7
--- /dev/null
+++ b/tests/test_tracing.py
@@ -0,0 +1,57 @@
+import ddtrace
+
+from xocto import tracing
+
+
+class TestSetTags:
+    def test_single_string_tag(self, mocker):
+        span = ddtrace.Span(name="active-span")
+        mocker.patch("xocto.tracing.ddtrace.tracer.current_span", return_value=span)
+        assert tracing.set_tags({"foo": "bar"}) is None
+        assert span.get_tag("foo") == "bar"
+
+    def test_single_bytes_tag(self, mocker):
+        span = ddtrace.Span(name="active-span")
+        mocker.patch("xocto.tracing.ddtrace.tracer.current_span", return_value=span)
+        assert tracing.set_tags({"foo": b"bar"}) is None
+        # bytes cast to str in Python 3, unicode in Python 2 (Python 2 not tested)
+        # see https://ddtrace.readthedocs.io/en/stable/api.html#ddtrace.Span.set_tag_str
+        assert span.get_tag("foo") == str(b"bar")
+
+    def test_multiple_string_tags(self, mocker):
+        span = ddtrace.Span(name="active-span")
+        mocker.patch("xocto.tracing.ddtrace.tracer.current_span", return_value=span)
+        tags = {"foo": "bar", "animal": "cat"}
+        assert tracing.set_tags(tags) is None
+        assert span.get_tag("foo") == "bar"
+        assert span.get_tag("animal") == "cat"
+
+    def test_multiple_mixed_type_tags(self, mocker):
+        span = ddtrace.Span(name="active-span")
+        mocker.patch("xocto.tracing.ddtrace.tracer.current_span", return_value=span)
+        tags = {"foo": "bar", "animal": b"cat"}
+        assert tracing.set_tags(tags) is None
+        assert span.get_tag("foo") == "bar"
+        assert span.get_tag("animal") == str(b"cat")
+
+
+class TestSetTag:
+    def test_single_string_tag(self, mocker):
+        span = ddtrace.Span(name="active-span")
+        mocker.patch("xocto.tracing.ddtrace.tracer.current_span", return_value=span)
+        assert tracing.set_tag(key="foo", value="bar") is None
+        assert span.get_tag("foo") == "bar"
+
+    def test_single_bytes_tag(self, mocker):
+        span = ddtrace.Span(name="active-span")
+        mocker.patch("xocto.tracing.ddtrace.tracer.current_span", return_value=span)
+        assert tracing.set_tag(key="foo", value=b"bar") is None
+        assert span.get_tag("foo") == str(b"bar")
+
+
+class TestSetGlobalTag:
+    def test_set_string_tag(self, mocker):
+        span = ddtrace.Span(name="root-span")
+        mocker.patch("xocto.tracing.ddtrace.tracer.current_root_span", return_value=span)
+        assert tracing.set_global_tag(key="foo", value="bar") is None
+        assert span.get_tag("foo") == "bar"