Return certificates by certs fixture.

tests/conftest.py

@@ -35,6 +35,10 @@ def self_signed_cert(test_dir, name):
     (test_dir / f"{name}.crt").write_text(
         crypto.dump_certificate(crypto.FILETYPE_PEM, cert).decode("utf-8")
     )
+    return (
+        crypto.dump_privatekey(crypto.FILETYPE_PEM, k),
+        crypto.dump_certificate(crypto.FILETYPE_PEM, cert),
+    )
 
 
 @pytest.fixture(scope="session")
@@ -97,4 +101,4 @@ def nginx(testdir, pytestconfig, nginx_config, certs, logger, otelcol):
 
 @pytest.fixture(scope="module")
 def certs(testdir):
-    self_signed_cert(testdir, "localhost")
+    yield self_signed_cert(testdir, "localhost")

tests/trace_service.py

@@ -45,14 +45,7 @@ def trace_service(request, pytestconfig, testdir, logger, certs):
     listen_addr = f"127.0.0.1:{24317 if trace_service.use_otelcol else 14317}"
     server.add_insecure_port(listen_addr)
     if pytestconfig.option.otelcol is None:
-        creds = grpc.ssl_server_credentials(
-            [
-                (
-                    (testdir / "localhost.key").read_text().encode(),
-                    (testdir / "localhost.crt").read_text().encode(),
-                )
-            ]
-        )
+        creds = grpc.ssl_server_credentials([certs])
         server.add_secure_port("127.0.0.1:14318", creds)
         listen_addr += " and 127.0.0.1:14318"
     logger.info(f"Starting trace service at {listen_addr}...")