tests: Make tests runnable from anywhere

tests/test_catalog.py

@@ -939,7 +939,7 @@ def test_collections_cache_correctly(self) -> None:
 
     def test_reading_iterating_and_writing_works_as_expected(self) -> None:
         """Test case to cover issue #88"""
-        stac_uri = "tests/data-files/catalogs/test-case-6/catalog.json"
+        stac_uri = TestCases.get_path("data-files/catalogs/test-case-6/catalog.json")
         cat = Catalog.from_file(stac_uri)
 
         # Iterate over the items. This was causing failure in

tests/test_item_collection.py

@@ -2,6 +2,8 @@
 import json
 from pystac.item_collection import ItemCollection
 import unittest
+from os.path import relpath
+
 import pystac
 
 from tests.utils import TestCases
@@ -101,7 +103,11 @@ def test_raise_error_for_invalid_object(self) -> None:
 
     def test_from_relative_path(self) -> None:
         _ = pystac.ItemCollection.from_file(
-            "./tests/data-files/item-collection/sample-item-collection.json"
+            relpath(
+                TestCases.get_path(
+                    "data-files/item-collection/sample-item-collection.json"
+                )
+            )
         )
 
     def test_from_list_of_dicts(self) -> None:

tests/test_utils.py

@@ -8,6 +8,7 @@
 from pystac import utils
 
 from pystac.utils import make_relative_href, make_absolute_href, is_absolute_href
+from tests.utils import TestCases
 
 
 class UtilsTest(unittest.TestCase):
@@ -273,7 +274,9 @@ def test_datetime_to_str(self) -> None:
 
     def test_geojson_bbox(self) -> None:
         # Use sample Geojson from https://en.wikipedia.org/wiki/GeoJSON
-        with open("tests/data-files/geojson/sample.geojson") as sample_geojson:
+        with open(
+            TestCases.get_path("data-files/geojson/sample.geojson")
+        ) as sample_geojson:
             all_features = json.load(sample_geojson)
             geom_dicts = [f["geometry"] for f in all_features["features"]]
             for geom in geom_dicts: