Test prefix maps using bioregistry's epm as reference. (#406)

Drafted with @matentzn  over a call.

tests/test_prefixes.py

@@ -0,0 +1,18 @@
+"""Test for built-in prefixes."""
+
+import unittest
+
+from sssom.context import get_extended_prefix_map, get_jsonld_context
+
+
+class TestPrefix(unittest.TestCase):
+    """A test case for testing prefixes using EPM."""
+
+    def test_builtin_prefixes(self):
+        """This test ensures that the bioregistry managed EPM (extended prefix-map) does not deviate from the fixed SSSOM built-in prefixes."""
+        prefix_map = get_extended_prefix_map()
+        sssom_schema_context = get_jsonld_context()
+        for k, v in prefix_map.items():
+            if isinstance(v, str):
+                if k in sssom_schema_context["@context"]:
+                    self.assertTrue(sssom_schema_context["@context"][k] == v)