text: import datetime as dt
  
  import pytest
  import pytz
  
  import stix2
  
  from .constants import IDENTITY_ID, INDICATOR_ID, SIGHTING_ID, SIGHTING_KWARGS
  
  EXPECTED_SIGHTING = """{
      "type": "sighting",
      "id": "sighting--bfbc19db-ec35-4e45-beed-f8bde2a772fb",
      "created": "2016-04-06T20:06:37.000Z",
      "modified": "2016-04-06T20:06:37.000Z",
      "sighting_of_ref": "indicator--a740531e-63ff-4e49-a9e1-a0a3eed0e3e7",
      "where_sighted_refs": [
          "identity--311b2d2d-f010-4473-83ec-1edf84858f4c"
      ]
  }"""
  
  BAD_SIGHTING = """{
      "created": "2016-04-06T20:06:37.000Z",
      "id": "sighting--bfbc19db-ec35-4e45-beed-f8bde2a772fb",
      "modified": "2016-04-06T20:06:37.000Z",
      "sighting_of_ref": "indicator--a740531e-63ff-4e49-a9e1-a0a3eed0e3e7",
      "type": "sighting",
      "where_sighted_refs": [
          "malware--8cc7afd6-5455-4d2b-a736-e614ee631d99"
      ]
  }"""
  
  
  def test_sighting_all_required_properties():
      now = dt.datetime(2016, 4, 6, 20, 6, 37, tzinfo=pytz.utc)
  
      s = stix2.v20.Sighting(
          type='sighting',
          id=SIGHTING_ID,
          created=now,
          modified=now,
          sighting_of_ref=INDICATOR_ID,
          where_sighted_refs=[IDENTITY_ID],
      )
      assert str(s) == EXPECTED_SIGHTING
  
  
  def test_sighting_bad_where_sighted_refs():
      now = dt.datetime(2016, 4, 6, 20, 6, 37, tzinfo=pytz.utc)
  
      with pytest.raises(stix2.exceptions.InvalidValueError) as excinfo:
          stix2.v20.Sighting(
              type='sighting',
              id=SIGHTING_ID,
              created=now,
              modified=now,
              sighting_of_ref=INDICATOR_ID,
              where_sighted_refs=["malware--8cc7afd6-5455-4d2b-a736-e614ee631d99"],
          )
  
      assert excinfo.value.cls == stix2.v20.Sighting
      assert excinfo.value.prop_name == "where_sighted_refs"
      assert excinfo.value.reason == "must start with 'identity'."
      assert str(excinfo.value) == "Invalid value for Sighting 'where_sighted_refs': must start with 'identity'."
  
  
  def test_sighting_type_must_be_sightings():
      with pytest.raises(stix2.exceptions.InvalidValueError) as excinfo:
          stix2.v20.Sighting(type='xxx', **SIGHTING_KWARGS)
  
      assert excinfo.value.cls == stix2.v20.Sighting
      assert excinfo.value.prop_name == "type"
      assert excinfo.value.reason == "must equal 'sighting'."
      assert str(excinfo.value) == "Invalid value for Sighting 'type': must equal 'sighting'."
  
  
  def test_invalid_kwarg_to_sighting():
      with pytest.raises(stix2.exceptions.ExtraPropertiesError) as excinfo:
          stix2.v20.Sighting(my_custom_property="foo", **SIGHTING_KWARGS)
  
      assert excinfo.value.cls == stix2.v20.Sighting
      assert excinfo.value.properties == ['my_custom_property']
      assert str(excinfo.value) == "Unexpected properties for Sighting: (my_custom_property)."
  
  
  def test_create_sighting_from_objects_rather_than_ids(malware):  # noqa: F811
      rel = stix2.v20.Sighting(sighting_of_ref=malware)
  
      assert rel.sighting_of_ref == 'malware--00000000-0000-4000-8000-000000000001'
      assert rel.id == 'sighting--00000000-0000-4000-8000-000000000003'
  
  
  @pytest.mark.parametrize(
      "data", [
          EXPECTED_SIGHTING,
          {
              "created": "2016-04-06T20:06:37Z",
              "id": SIGHTING_ID,
              "modified": "2016-04-06T20:06:37Z",
              "sighting_of_ref": "indicator--a740531e-63ff-4e49-a9e1-a0a3eed0e3e7",
              "type": "sighting",
              "where_sighted_refs": [
                  IDENTITY_ID,
              ],
          },
      ],
  )
  def test_parse_sighting(data):
      sighting = stix2.parse(data, version="2.0")
  
      assert sighting.type == 'sighting'
      assert sighting.id == SIGHTING_ID
      assert sighting.created == dt.datetime(2016, 4, 6, 20, 6, 37, tzinfo=pytz.utc)
      assert sighting.modified == dt.datetime(2016, 4, 6, 20, 6, 37, tzinfo=pytz.utc)
      assert sighting.sighting_of_ref == INDICATOR_ID
      assert sighting.where_sighted_refs == [IDENTITY_ID]
  