imgtool: initial sanity test

An initial sanity test for imgtool is added, checks
different commands for key operations (keygen, getpriv,
getpub and getpubhash).

Also very basic test for sign / verify is added.

Some tests are disabled (marked as 'xfail') due to
the missing implementation.

Signed-off-by: Denis Mingulov <denis@mingulov.com>
diff --git a/scripts/tests/conftest.py b/scripts/tests/conftest.py
new file mode 100644
index 0000000..797bf25
--- /dev/null
+++ b/scripts/tests/conftest.py
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+# List of tests expected to fail for some reason
+XFAILED_TESTS = {
+    "tests/test_keys.py::test_getpriv[openssl-ed25519]",
+    "tests/test_keys.py::test_getpriv[openssl-x25519]",
+    "tests/test_keys.py::test_getpriv[pkcs8-rsa-2048]",
+    "tests/test_keys.py::test_getpriv[pkcs8-rsa-3072]",
+    "tests/test_keys.py::test_getpriv[pkcs8-ed25519]",
+    "tests/test_keys.py::test_getpub[pem-ed25519]",
+    "tests/test_keys.py::test_sign_verify[x25519]",
+}
+
+
+def pytest_runtest_setup(item):
+    if item.nodeid in XFAILED_TESTS:
+        pytest.xfail()