diff --git a/opencensus/trace/propagation/binary_format.py b/opencensus/trace/propagation/binary_format.py
index b73492bad..3d078ab6b 100644
--- a/opencensus/trace/propagation/binary_format.py
+++ b/opencensus/trace/propagation/binary_format.py
@@ -17,7 +17,7 @@
 import logging
 import struct
 
-from opencensus.trace.span_context import SpanContext
+from opencensus.trace import span_context as span_context_module
 from opencensus.trace.trace_options import TraceOptions
 
 # Used for decoding hex bytes to hex string.
@@ -54,7 +54,7 @@
         trace_id_field_id=UNSIGNED_CHAR,
         trace_id='{}{}'.format(TRACE_ID_SIZE, CHAR_ARRAY_FORMAT),
         span_id_field_id=UNSIGNED_CHAR,
-        span_id=UNSIGNED_LONG_LONG,
+        span_id='{}{}'.format(SPAN_ID_SIZE, CHAR_ARRAY_FORMAT),
         trace_option_field_id=UNSIGNED_CHAR,
         trace_option=UNSIGNED_CHAR)
 
@@ -80,15 +80,15 @@ class BinaryFormatPropagator(object):
         [SpanContext]
             trace_id: hex string with length 32.
                 e.g. 'a0b72ca15c1a4bd18962d0ac59dc90b9'
-            span_id: 64 bits integer.
-                e.g. 7433567179112518326
+            span_id: hex string with length 16.
+                e.g. 'a0b72ca15c1a4bd1'
             enabled (trace option): bool.
                 e.g. True
         [Binary Format]
             trace_id: Bytes with length 16.
                 e.g. b'\xa0\xb7,\xa1\\\x1aK\xd1\x89b\xd0\xacY\xdc\x90\xb9'
             span_id: Bytes with length 8.
-                e.g. b'\xb6\x12\x01\xf5\xf6U)g'
+                e.g. b'\x00\xf0g\xaa\x0b\xa9\x02\xb7'
             trace_option: Byte with length 1.
                 e.g. b'\x01'
     """
@@ -106,25 +106,28 @@ def from_header(self, binary):
         """
         # If no binary provided, generate a new SpanContext
         if binary is None:
-            return SpanContext(from_header=False)
+            return span_context_module.SpanContext(from_header=False)
 
         # If cannot parse, return a new SpanContext and ignore the context
         # from binary.
         try:
             data = Header._make(struct.unpack(BINARY_FORMAT, binary))
         except struct.error:
-            logging.warn('Cannot parse the incoming binary data {}, '
-                         'wrong format. Total bytes length should be {}.'
-                         .format(binary, FORMAT_LENGTH))
-            return SpanContext(from_header=False)
+            logging.warning(
+                'Cannot parse the incoming binary data {}, '
+                'wrong format. Total bytes length should be {}.'.format(
+                    binary, FORMAT_LENGTH
+                )
+            )
+            return span_context_module.SpanContext(from_header=False)
 
         # data.trace_id is in bytes with length 16, hexlify it to hex bytes
         # with length 32, then decode it to hex string using utf-8.
         trace_id = str(binascii.hexlify(data.trace_id).decode(UTF8))
-        span_id = data.span_id
+        span_id = str(binascii.hexlify(data.span_id).decode(UTF8))
         trace_options = TraceOptions(data.trace_option)
 
-        span_context = SpanContext(
+        span_context = span_context_module.SpanContext(
                 trace_id=trace_id,
                 span_id=span_id,
                 trace_options=trace_options,
@@ -149,7 +152,7 @@ def to_header(self, span_context):
         # If there is no span_id in this context, set it to 0, which is
         # considered invalid and won't be set as the downstream parent span_id.
         if span_id is None:
-            span_id = 0
+            span_id = span_context_module.INVALID_SPAN_ID
 
         # Convert trace_id to bytes with length 16, treat span_id as 64 bit
         # integer which is unsigned long long type and convert it to bytes with
@@ -160,6 +163,6 @@ def to_header(self, span_context):
             TRACE_ID_FIELD_ID,
             binascii.unhexlify(trace_id),
             SPAN_ID_FIELD_ID,
-            span_id,
+            binascii.unhexlify(span_id),
             TRACE_OPTION_FIELD_ID,
             trace_options)
diff --git a/opencensus/trace/propagation/google_cloud_format.py b/opencensus/trace/propagation/google_cloud_format.py
index 1c1b607e8..8c635dd73 100644
--- a/opencensus/trace/propagation/google_cloud_format.py
+++ b/opencensus/trace/propagation/google_cloud_format.py
@@ -18,7 +18,7 @@
 from opencensus.trace.span_context import SpanContext
 from opencensus.trace.trace_options import TraceOptions
 
-_TRACE_CONTEXT_HEADER_FORMAT = '([0-9a-f]{32})(\/(\d+))?(;o=(\d+))?'
+_TRACE_CONTEXT_HEADER_FORMAT = '([0-9a-f]{32})(\/([0-9a-f]{16}))?(;o=(\d+))?'
 _TRACE_CONTEXT_HEADER_RE = re.compile(_TRACE_CONTEXT_HEADER_FORMAT)
 _TRACE_ID_DELIMETER = '/'
 _SPAN_ID_DELIMETER = ';'
diff --git a/opencensus/trace/propagation/trace_context_http_header_format.py b/opencensus/trace/propagation/trace_context_http_header_format.py
index 1098ffba2..3ac3301f6 100644
--- a/opencensus/trace/propagation/trace_context_http_header_format.py
+++ b/opencensus/trace/propagation/trace_context_http_header_format.py
@@ -61,7 +61,7 @@ def from_header(self, header):
                 # Need to convert span_id from hex string to int
                 span_context = SpanContext(
                     trace_id=trace_id,
-                    span_id=int(span_id, 16),
+                    span_id=span_id,
                     trace_options=TraceOptions(trace_options),
                     from_header=True)
                 return span_context
@@ -90,10 +90,6 @@ def to_header(self, span_context):
         span_id = span_context.span_id
         trace_options = span_context.trace_options.enabled
 
-        # Need to convert span_id from int to hex string
-        span_id_hex = hex(span_id)
-        span_id = span_id_hex[2:].zfill(16)
-
         # Convert the trace options
         trace_options = '01' if trace_options else '00'
 
diff --git a/opencensus/trace/span_context.py b/opencensus/trace/span_context.py
index 97c02d961..e01c425e9 100644
--- a/opencensus/trace/span_context.py
+++ b/opencensus/trace/span_context.py
@@ -15,16 +15,17 @@
 """SpanContext encapsulates the current context within the request's trace."""
 
 import logging
-import random
 import re
 import uuid
 
 from opencensus.trace import trace_options
 
 _INVALID_TRACE_ID = '0' * 32
-_INVALID_SPAN_ID = 0
+INVALID_SPAN_ID = '0' * 16
 _TRACE_HEADER_KEY = 'X_CLOUD_TRACE_CONTEXT'
-_TRACE_ID_FORMAT = '[0-9a-f]{32}?'
+
+TRACE_ID_PATTERN = re.compile('[0-9a-f]{32}?')
+SPAN_ID_PATTERN = re.compile('[0-9a-f]{16}?')
 
 # Default options, enable tracing
 DEFAULT_OPTIONS = 1
@@ -42,8 +43,9 @@ class SpanContext(object):
     :param trace_id: (Optional) Trace_id is a 32 digits uuid for the trace.
                      If not given, will generate one automatically.
 
-    :type span_id: int
+    :type span_id: str
     :param span_id: (Optional) Identifier for the span, unique within a trace.
+                    If not given, will generate one automatically.
 
     :type trace_options: :class: `~opencensus.trace.trace_options.TraceOptions`
     :param trace_options: (Optional) TraceOptions indicates 8 trace options.
@@ -64,10 +66,10 @@ def __init__(
         if trace_options is None:
             trace_options = DEFAULT
 
-        self.trace_id = self.check_trace_id(trace_id)
-        self.span_id = self.check_span_id(span_id)
-        self.trace_options = trace_options
         self.from_header = from_header
+        self.trace_id = self._check_trace_id(trace_id)
+        self.span_id = self._check_span_id(span_id)
+        self.trace_options = trace_options
 
     def __str__(self):
         """Returns a string form of the SpanContext. This is the format of
@@ -84,41 +86,42 @@ def __str__(self):
             int(enabled))
         return header
 
-    def check_span_id(self, span_id):
-        """Check the type of span_id to ensure it is int. If it is not int,
-        first try to convert it to int, if failed to convert, then log a
-        warning message and set the span_id to None.
+    def _check_span_id(self, span_id):
+        """Check the format of the span_id to ensure it is 16-character hex
+        value representing a 64-bit number. If span_id is invalid, logs a
+        warning message and returns None
 
-        :type span_id: int
-        :param span_id: Identifier for the span, unique within a trace.
+        :type span_id: str
+        :param span_id: Identifier for the span, unique within a span.
 
-        :rtype: int
+        :rtype: str
         :returns: Span_id for the current span.
         """
         if span_id is None:
             return None
+        assert isinstance(span_id, str)
 
-        if span_id == 0:
+        if span_id is INVALID_SPAN_ID:
             logging.warning(
-                'Span_id {} is invalid, cannot be zero.'.format(span_id))
+                'Span_id {} is invalid (cannot be all zero)'.format(span_id))
             self.from_header = False
             return None
 
-        if not isinstance(span_id, int):
-            try:
-                span_id = int(span_id)
-            except (TypeError, ValueError):
-                logging.warning(
-                    'The type of span_id should be int, got {}.'.format(
-                        span_id.__class__.__name__))
-                self.from_header = False
-                span_id = None
+        match = SPAN_ID_PATTERN.match(span_id)
 
-        return span_id
+        if match:
+            return span_id
+        else:
+            logging.warning(
+                'Span_id {} does not the match the '
+                'required format'.format(span_id))
+            self.from_header = False
+            return None
 
-    def check_trace_id(self, trace_id):
+    def _check_trace_id(self, trace_id):
         """Check the format of the trace_id to ensure it is 32-character hex
-        value representing a 128-bit number. Also the trace_id cannot be zero.
+        value representing a 128-bit number. If trace_id is invalid, returns a
+        randomly generated trace id
 
         :type trace_id: str
         :param trace_id:
@@ -131,41 +134,39 @@ def check_trace_id(self, trace_id):
         if trace_id is _INVALID_TRACE_ID:
             logging.warning(
                 'Trace_id {} is invalid (cannot be all zero), '
-                'generate a new one.'.format(trace_id))
+                'generating a new one.'.format(trace_id))
             self.from_header = False
             return generate_trace_id()
 
-        trace_id_pattern = re.compile(_TRACE_ID_FORMAT)
-
-        match = trace_id_pattern.match(trace_id)
+        match = TRACE_ID_PATTERN.match(trace_id)
 
         if match:
             return trace_id
         else:
             logging.warning(
                 'Trace_id {} does not the match the required format,'
-                'generate a new one instead.'.format(trace_id))
+                'generating a new one instead.'.format(trace_id))
             self.from_header = False
             return generate_trace_id()
 
 
 def generate_span_id():
-    """Return the random generated span ID for a span. Must be 16 digits
-    as Stackdriver Trace V2 API only accepts 16 digits span ID.
+    """Return the random generated span ID for a span. Must be a 16 character
+    hexadecimal encoded string
 
-    :rtype: int
-    :returns: Identifier for the span. Must be a 64-bit integer other
-              than 0 and unique within a trace.
+    :rtype: str
+    :returns: 16 digit randomly generated hex trace id.
     """
-    span_id = random.randint(10**15, 10**16 - 1)
+    span_id = uuid.uuid4().hex[:16]
     return span_id
 
 
 def generate_trace_id():
-    """Generate a trace_id randomly.
+    """Generate a trace_id randomly. Must be a 32 character
+    hexadecimal encoded string
 
     :rtype: str
-    :returns: 32 digit randomly generated trace ID.
+    :returns: 32 digit randomly generated hex trace id.
     """
     trace_id = uuid.uuid4().hex
     return trace_id
diff --git a/tests/system/trace/basic_trace/basic_trace_system_test.py b/tests/system/trace/basic_trace/basic_trace_system_test.py
index 2ba3803d7..d919249ba 100644
--- a/tests/system/trace/basic_trace/basic_trace_system_test.py
+++ b/tests/system/trace/basic_trace/basic_trace_system_test.py
@@ -32,7 +32,7 @@ def test_tracer(self):
         from opencensus.trace.propagation import google_cloud_format
 
         trace_id = 'f8739df974a4481f98748cd92b27177d'
-        span_id = '16971691944144156899'
+        span_id = '6e0c63257de34c92'
         trace_option = 1
 
         trace_header = '{}/{};o={}'.format(trace_id, span_id, trace_option)
diff --git a/tests/system/trace/django/django_system_test.py b/tests/system/trace/django/django_system_test.py
index 9871037df..5462c2260 100644
--- a/tests/system/trace/django/django_system_test.py
+++ b/tests/system/trace/django/django_system_test.py
@@ -43,7 +43,7 @@ def wait_app_to_start():
 def generate_header():
     """Generate a trace header."""
     trace_id = uuid.uuid4().hex
-    span_id = random.randint(10**15, 10**16 - 1)
+    span_id = uuid.uuid4().hex[:16]
     trace_option = 1
 
     header = '{}/{};o={}'.format(trace_id, span_id, trace_option)
diff --git a/tests/system/trace/flask/flask_system_test.py b/tests/system/trace/flask/flask_system_test.py
index 3ca0bc4e6..f7c20ae1f 100644
--- a/tests/system/trace/flask/flask_system_test.py
+++ b/tests/system/trace/flask/flask_system_test.py
@@ -42,7 +42,7 @@ def wait_app_to_start():
 def generate_header():
     """Generate a trace header."""
     trace_id = uuid.uuid4().hex
-    span_id = random.randint(10**15, 10**16 - 1)
+    span_id = uuid.uuid4().hex[:16]
     trace_option = 1
 
     header = '{}/{};o={}'.format(trace_id, span_id, trace_option)
diff --git a/tests/unit/trace/exporters/test_stackdriver_exporter.py b/tests/unit/trace/exporters/test_stackdriver_exporter.py
index 8cc989619..dfce4eb4e 100644
--- a/tests/unit/trace/exporters/test_stackdriver_exporter.py
+++ b/tests/unit/trace/exporters/test_stackdriver_exporter.py
@@ -144,7 +144,7 @@ def test_translate_to_stackdriver(self):
         project_id = 'PROJECT'
         trace_id = '6e0c63257de34c92bf9efcd03927272e'
         span_name = 'test span'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         attributes = {
             'attributeMap': {
                 'key': {
@@ -155,7 +155,7 @@ def test_translate_to_stackdriver(self):
                }
             }
         }
-        parent_span_id = 1111
+        parent_span_id = '6e0c63257de34c93'
         start_time = 'test start time'
         end_time = 'test end time'
         trace = {
diff --git a/tests/unit/trace/exporters/test_zipkin_exporter.py b/tests/unit/trace/exporters/test_zipkin_exporter.py
index 69035c939..34715da8e 100644
--- a/tests/unit/trace/exporters/test_zipkin_exporter.py
+++ b/tests/unit/trace/exporters/test_zipkin_exporter.py
@@ -98,8 +98,8 @@ def test_translate_to_zipkin_span_kind_none(self):
             span_data_module.SpanData(
                 name='child_span',
                 context=span_context.SpanContext(trace_id=trace_id),
-                span_id=1234567890,
-                parent_span_id=1111111111,
+                span_id='6e0c63257de34c92',
+                parent_span_id='6e0c63257de34c93',
                 attributes={'test_key': 'test_value'},
                 start_time='2017-08-15T18:02:26.071158Z',
                 end_time='2017-08-15T18:02:36.071158Z',
@@ -114,8 +114,8 @@ def test_translate_to_zipkin_span_kind_none(self):
             span_data_module.SpanData(
                 name='child_span',
                 context=span_context.SpanContext(trace_id=trace_id),
-                span_id=1234567890,
-                parent_span_id=1111111111,
+                span_id='6e0c63257de34c92',
+                parent_span_id='6e0c63257de34c93',
                 attributes={'test_key': 1},
                 start_time='2017-08-15T18:02:26.071158Z',
                 end_time='2017-08-15T18:02:36.071158Z',
@@ -134,7 +134,7 @@ def test_translate_to_zipkin_span_kind_none(self):
             span_data_module.SpanData(
                 name='child_span',
                 context=span_context.SpanContext(trace_id=trace_id),
-                span_id=1234567890,
+                span_id='6e0c63257de34c92',
                 parent_span_id=None,
                 attributes={
                     'test_key': False,
@@ -172,8 +172,8 @@ def test_translate_to_zipkin_span_kind_none(self):
         expected_zipkin_spans_ipv4 = [
             {
                 'traceId': '6e0c63257de34c92bf9efcd03927272e',
-                'id': '1234567890',
-                'parentId': '1111111111',
+                'id': '6e0c63257de34c92',
+                'parentId': '6e0c63257de34c93',
                 'name': 'child_span',
                 'timestamp': 1502820146000000,
                 'duration': 10000000,
@@ -182,8 +182,8 @@ def test_translate_to_zipkin_span_kind_none(self):
             },
             {
                 'traceId': '6e0c63257de34c92bf9efcd03927272e',
-                'id': '1234567890',
-                'parentId': '1111111111',
+                'id': '6e0c63257de34c92',
+                'parentId': '6e0c63257de34c93',
                 'name': 'child_span',
                 'timestamp': 1502820146000000,
                 'duration': 10000000,
@@ -195,7 +195,7 @@ def test_translate_to_zipkin_span_kind_none(self):
         expected_zipkin_spans_ipv6 = [
             {
                 'traceId': '6e0c63257de34c92bf9efcd03927272e',
-                'id': '1234567890',
+                'id': '6e0c63257de34c92',
                 'name': 'child_span',
                 'timestamp': 1502820146000000,
                 'duration': 10000000,
diff --git a/tests/unit/trace/ext/django/test_middleware.py b/tests/unit/trace/ext/django/test_middleware.py
index fd44eff0c..53ddcf959 100644
--- a/tests/unit/trace/ext/django/test_middleware.py
+++ b/tests/unit/trace/ext/django/test_middleware.py
@@ -12,9 +12,21 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import unittest
+
 import mock
+from django.test import RequestFactory
+from django.test.utils import teardown_test_environment
 
-import unittest
+from opencensus.trace import execution_context
+from opencensus.trace.exporters import print_exporter
+from opencensus.trace.exporters import zipkin_exporter
+from opencensus.trace.exporters.transports import sync
+from opencensus.trace.ext import utils
+from opencensus.trace.propagation import google_cloud_format
+from opencensus.trace.samplers import always_on
+from opencensus.trace.samplers import probability
+from opencensus.trace.tracers import base
 
 
 class TestOpencensusMiddleware(unittest.TestCase):
@@ -28,18 +40,11 @@ def setUp(self):
         setup_test_environment()
 
     def tearDown(self):
-        from django.test.utils import teardown_test_environment
-        from opencensus.trace import execution_context
-
         execution_context.clear()
-
         teardown_test_environment()
 
     def test_constructor_cloud(self):
         from opencensus.trace.ext.django import middleware
-        from opencensus.trace.samplers import always_on
-        from opencensus.trace.propagation import google_cloud_format
-        from opencensus.trace.exporters.transports import sync
 
         class MockCloudExporter(object):
             def __init__(self, project_id, transport):
@@ -83,9 +88,6 @@ def __init__(self, project_id, transport):
 
     def test_constructor_zipkin(self):
         from opencensus.trace.ext.django import middleware
-        from opencensus.trace.samplers import always_on
-        from opencensus.trace.exporters import zipkin_exporter
-        from opencensus.trace.propagation import google_cloud_format
 
         service_name = 'test_service'
         host_name = 'test_hostname'
@@ -129,9 +131,6 @@ def test_constructor_zipkin(self):
 
     def test_constructor_probability_sampler(self):
         from opencensus.trace.ext.django import middleware
-        from opencensus.trace.samplers import probability
-        from opencensus.trace.exporters import print_exporter
-        from opencensus.trace.propagation import google_cloud_format
 
         rate = 0.8
         params = {
@@ -171,12 +170,10 @@ def test_constructor_probability_sampler(self):
         self.assertEqual(middleware.sampler.rate, rate)
 
     def test_process_request(self):
-        from django.test import RequestFactory
-
         from opencensus.trace.ext.django import middleware
 
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 123
+        span_id = '6e0c63257de34c92'
         django_trace_id = '{}/{}'.format(trace_id, span_id)
 
         django_request = RequestFactory().get('/', **{
@@ -208,21 +205,15 @@ def test_process_request(self):
         self.assertEqual(span.name, 'mock.mock.Mock')
 
     def test_blacklist_path(self):
-        from django.test import RequestFactory
-
         from opencensus.trace.ext.django import middleware
-        from opencensus.trace.tracers import base
-        from opencensus.trace.tracers import noop_tracer
-        from opencensus.trace.ext import utils
-        from opencensus.trace import execution_context
 
         execution_context.clear()
 
-        blacklist_paths = ['test_blacklist_path',]
+        blacklist_paths = ['test_blacklist_path', ]
         params = {
-            'BLACKLIST_PATHS': ['test_blacklist_path',],
+            'BLACKLIST_PATHS': ['test_blacklist_path', ],
             'TRANSPORT':
-                'opencensus.trace.exporters.transports.sync.SyncTransport',}
+                'opencensus.trace.exporters.transports.sync.SyncTransport', }
         patch_params = mock.patch(
             'opencensus.trace.ext.django.middleware.settings.params',
             params)
@@ -262,12 +253,10 @@ def test_blacklist_path(self):
         assert isinstance(span, base.NullContextManager)
 
     def test_process_response(self):
-        from django.test import RequestFactory
-
         from opencensus.trace.ext.django import middleware
 
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 123
+        span_id = '6e0c63257de34c92'
         django_trace_id = '{}/{}'.format(trace_id, span_id)
 
         django_request = RequestFactory().get('/', **{
@@ -304,7 +293,6 @@ def test_process_response(self):
 
 
 class Test__set_django_attributes(unittest.TestCase):
-
     class Tracer(object):
         def __init__(self):
             self.attributes = {}
@@ -313,8 +301,8 @@ def add_attribute_to_current_span(self, key, value):
             self.attributes[key] = value
 
     def test__set_django_attributes_no_user(self):
-        from opencensus.trace.ext.django.middleware import _set_django_attributes
-
+        from opencensus.trace.ext.django.middleware import \
+            _set_django_attributes
         tracer = self.Tracer()
         request = mock.Mock()
 
@@ -327,8 +315,8 @@ def test__set_django_attributes_no_user(self):
         self.assertEqual(tracer.attributes, expected_attributes)
 
     def test__set_django_attributes_no_user_info(self):
-        from opencensus.trace.ext.django.middleware import _set_django_attributes
-
+        from opencensus.trace.ext.django.middleware import \
+            _set_django_attributes
         tracer = self.Tracer()
         request = mock.Mock()
         django_user = mock.Mock()
@@ -344,8 +332,8 @@ def test__set_django_attributes_no_user_info(self):
         self.assertEqual(tracer.attributes, expected_attributes)
 
     def test__set_django_attributes_with_user_info(self):
-        from opencensus.trace.ext.django.middleware import _set_django_attributes
-
+        from opencensus.trace.ext.django.middleware import \
+            _set_django_attributes
         tracer = self.Tracer()
         request = mock.Mock()
         django_user = mock.Mock()
diff --git a/tests/unit/trace/ext/flask/test_flask_middleware.py b/tests/unit/trace/ext/flask/test_flask_middleware.py
index 1f7e7d598..0c172fe0b 100644
--- a/tests/unit/trace/ext/flask/test_flask_middleware.py
+++ b/tests/unit/trace/ext/flask/test_flask_middleware.py
@@ -17,17 +17,23 @@
 
 import unittest
 
+import flask
 import mock
 
+from opencensus.trace import execution_context
+from opencensus.trace.exporters import print_exporter
 from opencensus.trace.ext.flask import flask_middleware
+from opencensus.trace.propagation import google_cloud_format
+from opencensus.trace.samplers import always_off
+from opencensus.trace.samplers import always_on
+from opencensus.trace.tracers import base
+from opencensus.trace.tracers import noop_tracer
 
 
 class TestFlaskMiddleware(unittest.TestCase):
 
     @staticmethod
     def create_app():
-        import flask
-
         app = flask.Flask(__name__)
 
         @app.route('/')
@@ -46,10 +52,6 @@ def tearDown(self):
         execution_context.clear()
 
     def test_constructor_default(self):
-        from opencensus.trace.exporters import print_exporter
-        from opencensus.trace.samplers import always_on
-        from opencensus.trace.propagation import google_cloud_format
-
         app = mock.Mock()
         middleware = flask_middleware.FlaskMiddleware(app=app)
 
@@ -86,7 +88,7 @@ def test__before_request(self):
 
         flask_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         flask_trace_id = '{}/{}'.format(trace_id, span_id)
 
         app = self.create_app()
@@ -114,13 +116,9 @@ def test__before_request(self):
             self.assertEqual(span_context.trace_id, trace_id)
 
     def test__before_request_blacklist(self):
-        from opencensus.trace import execution_context
-        from opencensus.trace.tracers import base
-        from opencensus.trace.tracers import noop_tracer
-
         flask_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         flask_trace_id = '{}/{}'.format(trace_id, span_id)
 
         app = self.create_app()
@@ -144,12 +142,10 @@ def test_header_encoding(self):
         # This test case is expected to fail at the check_trace_id method
         # in SpanContext because it cannot match the pattern for trace_id,
         # And a new trace_id will generate for the context.
-        from opencensus.trace import execution_context
-        from opencensus.trace.tracers import base
 
         flask_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = "你好"
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         flask_trace_id = '{}/{}'.format(trace_id, span_id)
 
         app = self.create_app()
@@ -177,9 +173,6 @@ def test_header_encoding(self):
             self.assertNotEqual(span_context.trace_id, trace_id)
 
     def test_header_is_none(self):
-        from opencensus.trace import execution_context
-        from opencensus.trace.tracers import base
-
         app = self.create_app()
         flask_middleware.FlaskMiddleware(app=app)
         context = app.test_request_context(
@@ -201,11 +194,9 @@ def test_header_is_none(self):
             assert isinstance(span.parent_span, base.NullContextManager)
 
     def test__after_request_not_sampled(self):
-        from opencensus.trace.samplers import always_off
-
         flask_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         flask_trace_id = '{}/{}'.format(trace_id, span_id)
         sampler = always_off.AlwaysOffSampler()
 
@@ -221,7 +212,7 @@ def test__after_request_not_sampled(self):
     def test__after_request_sampled(self):
         flask_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         flask_trace_id = '{}/{}'.format(trace_id, span_id)
 
         app = self.create_app()
@@ -234,12 +225,9 @@ def test__after_request_sampled(self):
         self.assertEqual(response.status_code, 200)
 
     def test__after_request_blacklist(self):
-        from opencensus.trace import execution_context
-        from opencensus.trace.tracers import noop_tracer
-
         flask_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         flask_trace_id = '{}/{}'.format(trace_id, span_id)
 
         app = self.create_app()
diff --git a/tests/unit/trace/ext/pyramid/test_pyramid_middleware.py b/tests/unit/trace/ext/pyramid/test_pyramid_middleware.py
index 0dbb21cbd..d12ab47f4 100644
--- a/tests/unit/trace/ext/pyramid/test_pyramid_middleware.py
+++ b/tests/unit/trace/ext/pyramid/test_pyramid_middleware.py
@@ -15,13 +15,23 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import mock
 import unittest
 
+import mock
 from pyramid.registry import Registry
 from pyramid.response import Response
 from pyramid.testing import DummyRequest
 
+from opencensus.trace import execution_context
+from opencensus.trace.exporters import print_exporter
+from opencensus.trace.exporters import zipkin_exporter
+from opencensus.trace.exporters.transports import sync
+from opencensus.trace.ext.pyramid import pyramid_middleware
+from opencensus.trace.propagation import google_cloud_format
+from opencensus.trace.samplers import always_on
+from opencensus.trace.tracers import base
+from opencensus.trace.tracers import noop_tracer
+
 
 class TestPyramidMiddleware(unittest.TestCase):
     def tearDown(self):
@@ -30,24 +40,20 @@ def tearDown(self):
         execution_context.clear()
 
     def test_constructor(self):
-        from opencensus.trace.ext.pyramid import pyramid_middleware
-        from opencensus.trace.samplers import always_on
-        from opencensus.trace.propagation import google_cloud_format
-        from opencensus.trace.exporters.transports import sync
-        from opencensus.trace.exporters import print_exporter
-
         pyramid_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         pyramid_trace_id = '{}/{}'.format(trace_id, span_id)
 
         response = Response()
+
         def dummy_handler(request):
             return response
 
         mock_registry = mock.Mock(spec=Registry)
         mock_registry.settings = {}
-        mock_registry.settings['OPENCENSUS_TRACE'] = {'EXPORTER': print_exporter.PrintExporter()}
+        mock_registry.settings['OPENCENSUS_TRACE'] = {
+            'EXPORTER': print_exporter.PrintExporter()}
 
         middleware = pyramid_middleware.OpenCensusTweenFactory(
             dummy_handler,
@@ -71,17 +77,12 @@ def dummy_handler(request):
         assert middleware(request) == response
 
     def test_constructor_zipkin(self):
-        from opencensus.trace.ext.pyramid import pyramid_middleware
-        from opencensus.trace.samplers import always_on
-        from opencensus.trace.exporters import zipkin_exporter
-        from opencensus.trace.propagation import google_cloud_format
-        from opencensus.trace.exporters.transports import sync
-
         service_name = 'test_service'
         host_name = 'test_hostname'
         port = 2333
 
         response = Response()
+
         def dummy_handler(request):
             return response
 
@@ -115,15 +116,13 @@ def dummy_handler(request):
         self.assertEqual(middleware.exporter.port, port)
 
     def test__before_request(self):
-        from opencensus.trace import execution_context
-        from opencensus.trace.ext.pyramid import pyramid_middleware
-
         pyramid_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         pyramid_trace_id = '{}/{}'.format(trace_id, span_id)
 
         response = Response()
+
         def dummy_handler(request):
             return response
 
@@ -159,17 +158,13 @@ def dummy_handler(request):
         self.assertEqual(span_context.trace_id, trace_id)
 
     def test__before_request_blacklist(self):
-        from opencensus.trace import execution_context
-        from opencensus.trace.tracers import base
-        from opencensus.trace.tracers import noop_tracer
-        from opencensus.trace.ext.pyramid import pyramid_middleware
-
         pyramid_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         pyramid_trace_id = '{}/{}'.format(trace_id, span_id)
 
         response = Response()
+
         def dummy_handler(request):
             return response
 
@@ -197,16 +192,13 @@ def dummy_handler(request):
         assert isinstance(span, base.NullContextManager)
 
     def test__after_request(self):
-        from opencensus.trace import execution_context
-        from opencensus.trace.ext.pyramid import pyramid_middleware
-        from opencensus.trace.samplers import always_off
-
         pyramid_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         pyramid_trace_id = '{}/{}'.format(trace_id, span_id)
 
         response = Response(status=200)
+
         def dummy_handler(request):
             return response
 
@@ -244,17 +236,13 @@ def dummy_handler(request):
         self.assertEqual(span.attributes, expected_attributes)
 
     def test__after_request_blacklist(self):
-        from opencensus.trace import execution_context
-        from opencensus.trace.tracers import base
-        from opencensus.trace.tracers import noop_tracer
-        from opencensus.trace.ext.pyramid import pyramid_middleware
-
         pyramid_trace_header = 'X_CLOUD_TRACE_CONTEXT'
         trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         pyramid_trace_id = '{}/{}'.format(trace_id, span_id)
 
         response = Response()
+
         def dummy_handler(request):
             return response
 
diff --git a/tests/unit/trace/propagation/test_binary_format.py b/tests/unit/trace/propagation/test_binary_format.py
index 769639a3e..8fd3e148e 100644
--- a/tests/unit/trace/propagation/test_binary_format.py
+++ b/tests/unit/trace/propagation/test_binary_format.py
@@ -39,12 +39,11 @@ def test_from_header_none(self):
         self.assertFalse(span_context.from_header)
 
     def test_from_header(self):
-        binary_header = b'\x00\x00\xa0\xb7,\xa1\\\x1aK\xd1\x89b\xd0' \
-                        b'\xacY\xdc\x90\xb9\x01g)U\xf6\xf5\x01\x12' \
-                        b'\xb6\x02\x01'
+        binary_header = b'\x00\x00\xa0\xb7,\xa1\\\x1aK\xd1\x89b\xd0\xacY\xdc' \
+                        b'\x90\xb9\x01\xa0\xb7,\xa1\\\x1aK\xd1\x02\x01'
 
         expected_trace_id = 'a0b72ca15c1a4bd18962d0ac59dc90b9'
-        expected_span_id = 7433567179112518326
+        expected_span_id = 'a0b72ca15c1a4bd1'
         expected_trace_option = True
 
         propagator = binary_format.BinaryFormatPropagator()
@@ -74,8 +73,8 @@ def test_to_header_span_id_zero(self):
         binary_header = propagator.to_header(span_context)
 
         expected_binary_header = b'\x00\x00\xa0\xb7,\xa1\\\x1aK\xd1\x89b\xd0' \
-                                 b'\xacY\xdc\x90\xb9\x01\x00\x00\x00\x00\x00' \
-                                 b'\x00\x00\x00\x02\x01'
+                                 b'\xacY\xdc\x90\xb9\x01\x00\x00\x00\x00' \
+                                 b'\x00\x00\x00\x00\x02\x01'
 
         self.assertEqual(expected_binary_header, binary_header)
 
@@ -85,7 +84,7 @@ def test_to_header(self):
 
         span_context = mock.Mock(spec=SpanContext)
         trace_id = 'a0b72ca15c1a4bd18962d0ac59dc90b9'
-        span_id = 7433567179112518326
+        span_id = 'a0b72ca15c1a4bd1'
         trace_options = '1'
         span_context.trace_id = trace_id
         span_context.span_id = span_id
@@ -95,8 +94,8 @@ def test_to_header(self):
 
         binary_header = propagator.to_header(span_context)
 
-        expected_binary_header = b'\x00\x00\xa0\xb7,\xa1\\\x1aK\xd1\x89b\xd0' \
-                                 b'\xacY\xdc\x90\xb9\x01g)U\xf6\xf5\x01\x12' \
-                                 b'\xb6\x02\x01'
+        expected_binary_header = b'\x00\x00\xa0\xb7,\xa1\\\x1aK' \
+                                 b'\xd1\x89b\xd0\xacY\xdc' \
+                                 b'\x90\xb9\x01\xa0\xb7,\xa1\\\x1aK\xd1\x02\x01'
 
         self.assertEqual(expected_binary_header, binary_header)
diff --git a/tests/unit/trace/propagation/test_google_cloud_format.py b/tests/unit/trace/propagation/test_google_cloud_format.py
index 3124f4a3d..b18e7d4aa 100644
--- a/tests/unit/trace/propagation/test_google_cloud_format.py
+++ b/tests/unit/trace/propagation/test_google_cloud_format.py
@@ -37,9 +37,9 @@ def test_header_type_error(self):
 
     def test_header_match(self):
         # Trace option is not enabled.
-        header = '6e0c63257de34c92bf9efcd03927272e/1234;o=0'
+        header = '6e0c63257de34c92bf9efcd03927272e/00f067aa0ba902b7;o=0'
         expected_trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        expected_span_id = 1234
+        expected_span_id = '00f067aa0ba902b7'
 
         propagator = google_cloud_format.GoogleCloudFormatPropagator()
         span_context = propagator.from_header(header)
@@ -49,9 +49,9 @@ def test_header_match(self):
         self.assertFalse(span_context.trace_options.enabled)
 
         # Trace option is enabled.
-        header = '6e0c63257de34c92bf9efcd03927272e/1234;o=1'
+        header = '6e0c63257de34c92bf9efcd03927272e/00f067aa0ba902b7;o=1'
         expected_trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        expected_span_id = 1234
+        expected_span_id = '00f067aa0ba902b7'
 
         propagator = google_cloud_format.GoogleCloudFormatPropagator()
         span_context = propagator.from_header(header)
@@ -61,9 +61,9 @@ def test_header_match(self):
         self.assertTrue(span_context.trace_options.enabled)
 
     def test_header_match_no_option(self):
-        header = '6e0c63257de34c92bf9efcd03927272e/1234'
+        header = '6e0c63257de34c92bf9efcd03927272e/00f067aa0ba902b7'
         expected_trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        expected_span_id = 1234
+        expected_span_id = '00f067aa0ba902b7'
 
         propagator = google_cloud_format.GoogleCloudFormatPropagator()
         span_context = propagator.from_header(header)
@@ -86,7 +86,7 @@ def test_to_header(self):
         from opencensus.trace import trace_options
 
         trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        span_id = 1234
+        span_id = '00f067aa0ba902b7'
         span_context = span_context.SpanContext(
             trace_id=trace_id,
             span_id=span_id,
diff --git a/tests/unit/trace/propagation/test_text_format.py b/tests/unit/trace/propagation/test_text_format.py
index 260b4e8a0..2b6fbf0e2 100644
--- a/tests/unit/trace/propagation/test_text_format.py
+++ b/tests/unit/trace/propagation/test_text_format.py
@@ -18,11 +18,12 @@
 
 from opencensus.trace.propagation import text_format
 
+
 class Test_from_carrier(unittest.TestCase):
 
     def test_from_carrier_keys_exist(self):
         test_trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        test_span_id = 1234
+        test_span_id = '00f067aa0ba902b7'
         test_options = 1
 
         carrier = {
@@ -53,7 +54,7 @@ def test_from_carrier_keys_not_exist(self):
 
     def test_to_carrier_has_span_id(self):
         test_trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        test_span_id = 1234
+        test_span_id = '00f067aa0ba902b7'
         test_options = '2'
 
         span_context = mock.Mock()
diff --git a/tests/unit/trace/propagation/test_trace_context_http_header_format.py b/tests/unit/trace/propagation/test_trace_context_http_header_format.py
index 4989cde70..dc75694f9 100644
--- a/tests/unit/trace/propagation/test_trace_context_http_header_format.py
+++ b/tests/unit/trace/propagation/test_trace_context_http_header_format.py
@@ -51,7 +51,7 @@ def test_header_match(self):
         # Trace option is not enabled.
         header = '00-6e0c63257de34c92bf9efcd03927272e-00f067aa0ba902b7-00'
         expected_trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        expected_span_id = 67667974448284343
+        expected_span_id = '00f067aa0ba902b7'
 
         propagator = trace_context_http_header_format.\
             TraceContextPropagator()
@@ -64,7 +64,7 @@ def test_header_match(self):
         # Trace option is enabled.
         header = '00-6e0c63257de34c92bf9efcd03927272e-00f067aa0ba902b7-01'
         expected_trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        expected_span_id = 67667974448284343
+        expected_span_id = '00f067aa0ba902b7'
 
         propagator = trace_context_http_header_format.\
             TraceContextPropagator()
@@ -77,7 +77,7 @@ def test_header_match(self):
     def test_header_match_no_option(self):
         header = '00-6e0c63257de34c92bf9efcd03927272e-00f067aa0ba902b7'
         expected_trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        expected_span_id = 67667974448284343
+        expected_span_id = '00f067aa0ba902b7'
 
         propagator = trace_context_http_header_format.\
             TraceContextPropagator()
@@ -102,11 +102,10 @@ def test_to_header(self):
         from opencensus.trace import trace_options
 
         trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        span_id = 67667974448284343
         span_id_hex = '00f067aa0ba902b7'
         span_context = span_context.SpanContext(
             trace_id=trace_id,
-            span_id=span_id,
+            span_id=span_id_hex,
             trace_options=trace_options.TraceOptions('1'))
 
         propagator = trace_context_http_header_format.\
diff --git a/tests/unit/trace/test_span_context.py b/tests/unit/trace/test_span_context.py
index 9011937f7..f137081e1 100644
--- a/tests/unit/trace/test_span_context.py
+++ b/tests/unit/trace/test_span_context.py
@@ -13,93 +13,114 @@
 # limitations under the License.
 
 import unittest
+from opencensus.trace import span_context as span_context_module
+from opencensus.trace.trace_options import TraceOptions
 
 
 class TestSpanContext(unittest.TestCase):
-
     project = 'PROJECT'
+    trace_id = '6e0c63257de34c92bf9efcd03927272e'
+    span_id = '6e0c63257de34c92'
 
     @staticmethod
     def _get_target_class():
-        from opencensus.trace.span_context import SpanContext
-
-        return SpanContext
+        return span_context_module.SpanContext
 
     def _make_one(self, *args, **kw):
         return self._get_target_class()(*args, **kw)
 
     def test_constructor(self):
-        trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        span_id = 1234
-
-        span_context = self._make_one(trace_id=trace_id, span_id=span_id)
+        span_context = self._make_one(
+            trace_id=self.trace_id,
+            span_id=self.span_id
+        )
 
-        self.assertEqual(span_context.trace_id, trace_id)
-        self.assertEqual(span_context.span_id, span_id)
+        self.assertEqual(span_context.trace_id, self.trace_id)
+        self.assertEqual(span_context.span_id, self.span_id)
 
     def test__str__(self):
-        from opencensus.trace.trace_options import TraceOptions
-        trace_id = '6e0c63257de34c92bf9efcd03927272e'
-        span_id = 1234
-
         span_context = self._make_one(
-            trace_id=trace_id,
-            span_id=span_id,
+            trace_id=self.trace_id,
+            span_id=self.span_id,
             trace_options=TraceOptions('1'))
 
-        header_expected = '6e0c63257de34c92bf9efcd03927272e/1234;o=1'
+        header_expected = '6e0c63257de34c92bf9efcd03927272e' \
+                          '/6e0c63257de34c92;o=1'
         header = span_context.__str__()
 
         self.assertEqual(header_expected, header)
 
     def test_check_span_id_none(self):
-        span_context = self._make_one(from_header=True)
-        span_id = span_context.check_span_id(None)
-        self.assertIsNone(span_id)
+        span_context = self._make_one(
+            trace_id=self.trace_id,
+            from_header=True)
+        self.assertIsNone(span_context.span_id)
 
     def test_check_span_id_zero(self):
-        span_context = self._make_one(from_header=True)
-        span_id = span_context.check_span_id(0)
+        span_context = self._make_one(
+            from_header=True,
+            trace_id=self.trace_id,
+            span_id=span_context_module.INVALID_SPAN_ID
+        )
         self.assertFalse(span_context.from_header)
-        self.assertIsNone(span_id)
+        self.assertIsNone(span_context.span_id)
 
-    def test_check_span_id_not_int(self):
-        span_id = {}
-        span_context = self._make_one()
-        span_id_checked = span_context.check_span_id(span_id)
-        self.assertIsNone(span_id_checked)
-        self.assertFalse(span_context.from_header)
+    def test_check_span_id_not_str(self):
+        with self.assertRaises(AssertionError):
+            self._make_one(
+                from_header=True,
+                trace_id=self.trace_id,
+                span_id={}
+            )
 
     def test_check_span_id_valid(self):
-        span_id = 1234
-        span_context = self._make_one(from_header=True)
-        span_id_checked = span_context.check_span_id(span_id)
-        self.assertEqual(span_id, span_id_checked)
+        span_context = self._make_one(
+            from_header=True,
+            trace_id=self.trace_id,
+            span_id=self.span_id
+        )
+        self.assertEqual(span_context.span_id, self.span_id)
 
     def test_check_trace_id_invalid(self):
-        from opencensus.trace.span_context import _INVALID_TRACE_ID
-
-        span_context = self._make_one(from_header=True)
-
-        trace_id_checked = span_context.check_trace_id(_INVALID_TRACE_ID)
+        span_context = self._make_one(
+            from_header=True,
+            trace_id=span_context_module._INVALID_TRACE_ID,
+            span_id=self.span_id
+        )
 
         self.assertFalse(span_context.from_header)
-        self.assertNotEqual(trace_id_checked, _INVALID_TRACE_ID)
+        self.assertNotEqual(
+            span_context.trace_id, span_context_module._INVALID_TRACE_ID
+        )
 
-    def test_check_trace_id_not_match(self):
+    def test_check_trace_id_invalid_format(self):
         trace_id_test = 'test_trace_id'
-
-        span_context = self._make_one(from_header=True)
-        trace_id_checked = span_context.check_trace_id(trace_id_test)
+        span_context = self._make_one(
+            from_header=True,
+            trace_id=trace_id_test,
+            span_id=self.span_id
+        )
 
         self.assertFalse(span_context.from_header)
-        self.assertNotEqual(trace_id_checked, trace_id_test)
-
-    def test_check_trace_id_match(self):
-        trace_id = '6e0c63257de34c92bf9efcd03927272e'
+        self.assertNotEqual(span_context.trace_id, trace_id_test)
 
-        span_context = self._make_one(from_header=True)
-        trace_id_checked = span_context.check_trace_id(trace_id)
+    def test_check_trace_id_valid_format(self):
+        span_context = self._make_one(
+            from_header=True,
+            trace_id=self.trace_id,
+            span_id=self.span_id
+        )
 
-        self.assertEqual(trace_id, trace_id_checked)
+        self.assertEqual(span_context.trace_id, self.trace_id)
         self.assertTrue(span_context.from_header)
+
+    def test_check_span_id_invalid_format(self):
+        span_id_test = 'test_trace_id'
+        span_context = self._make_one(
+            from_header=True,
+            trace_id=self.trace_id,
+            span_id=span_id_test
+        )
+
+        self.assertFalse(span_context.from_header)
+        self.assertIsNone(span_context.span_id)
diff --git a/tests/unit/trace/test_span_data.py b/tests/unit/trace/test_span_data.py
index e7dc85dad..8d50843e4 100644
--- a/tests/unit/trace/test_span_data.py
+++ b/tests/unit/trace/test_span_data.py
@@ -28,8 +28,8 @@ def test_create_span_data(self):
         span_data_module.SpanData(
             name='root',
             context=None,
-            span_id=2,
-            parent_span_id=1,
+            span_id='6e0c63257de34c92',
+            parent_span_id='6e0c63257de34c93',
             attributes={'key1': 'value1'},
             start_time=datetime.datetime.utcnow().isoformat() + 'Z',
             end_time=datetime.datetime.utcnow().isoformat() + 'Z',
@@ -46,8 +46,8 @@ def test_span_data_immutable(self):
         span_data = span_data_module.SpanData(
             name='root',
             context=None,
-            span_id=2,
-            parent_span_id=1,
+            span_id='6e0c63257de34c92',
+            parent_span_id='6e0c63257de34c93',
             attributes={'key1': 'value1'},
             start_time=datetime.datetime.utcnow().isoformat() + 'Z',
             end_time=datetime.datetime.utcnow().isoformat() + 'Z',
@@ -71,15 +71,15 @@ def test_format_legacy_trace_json(self):
             name='root',
             context=span_context.SpanContext(
                 trace_id=trace_id,
-                span_id=1111
+                span_id='6e0c63257de34c92'
             ),
-            span_id=2,
-            parent_span_id=1,
+            span_id='6e0c63257de34c92',
+            parent_span_id='6e0c63257de34c93',
             attributes={'key1': 'value1'},
             start_time=datetime.datetime.utcnow().isoformat() + 'Z',
             end_time=datetime.datetime.utcnow().isoformat() + 'Z',
             stack_trace=stack_trace.StackTrace(stack_trace_hash_id='111'),
-            links=[link.Link('1111', span_id='111')],
+            links=[link.Link('1111', span_id='6e0c63257de34c92')],
             status=status.Status(code=0, message='pok'),
             time_events=[
                 time_event.TimeEvent(
diff --git a/tests/unit/trace/tracers/test_context_tracer.py b/tests/unit/trace/tracers/test_context_tracer.py
index 2a2c2c5ee..69588ea37 100644
--- a/tests/unit/trace/tracers/test_context_tracer.py
+++ b/tests/unit/trace/tracers/test_context_tracer.py
@@ -20,7 +20,6 @@
 
 
 class TestContextTracer(unittest.TestCase):
-
     def test_constructor_defaults(self):
         from opencensus.trace import span_context
         from opencensus.trace.exporters import print_exporter
@@ -68,7 +67,7 @@ def test_finish_with_spans(self):
     def test_start_span(self, current_span_mock):
         from opencensus.trace import span_context
 
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         span_name = 'test_span'
         mock_span = mock.Mock()
         mock_span.span_id = span_id
@@ -87,7 +86,7 @@ def test_start_span(self, current_span_mock):
     def test_span(self, current_span_mock):
         from opencensus.trace import span_context
 
-        span_id = 1234
+        span_id = '6e0c63257de34c92'
         span_name = 'test_span'
         mock_span = mock.Mock()
         mock_span.span_id = span_id
@@ -126,7 +125,7 @@ def test_end_span_active(self, mock_current_span):
         mock_span.attributes = {}
         mock_span.__iter__ = mock.Mock(
             return_value=iter([mock_span]))
-        parent_span_id = 1234
+        parent_span_id = '6e0c63257de34c92'
         mock_span.parent_span.span_id = parent_span_id
         mock_current_span.return_value = mock_span
         tracer.end_span()
@@ -174,7 +173,7 @@ def test_end_span_batch_export(self, mock_current_span):
         mock_span.attributes = {}
         mock_span.__iter__ = mock.Mock(
             return_value=iter([mock_span]))
-        parent_span_id = 1234
+        parent_span_id = '6e0c63257de34c92'
         mock_span.parent_span.span_id = parent_span_id
         mock_current_span.return_value = mock_span
         tracer.end_span()