Added tests/ directory which mimics the one in the main BuildStream repo

tests/__init__.py

+# __init__.py

tests/docker-source.py

+import os
+import pytest

tests/dpkg-build.py

+import os
+import pytest

tests/project/elements/base.bst

+# elements/base.bst
+
+kind: stack
+depends:
+  - base/base-alpine.bst

tests/project/elements/base/base-alpine.bst

+kind: import
+
+description: |
+  Alpine Linux base for tests
+
+  Generated using the `tests/integration-tests/base/generate-base.sh` script.
+
+sources:
+  - kind: tar
+    url: https://gnome7.codethink.co.uk/tarballs/integration-tests-base.v1.x86_64.tar.xz
+    base-dir: ''
+    ref: 3eb559250ba82b64a68d86d0636a6b127aa5f6d25d3601a79f79214dc9703639

tests/project/project.conf

+# Project config for frontend build test
+name: test
+element-path: elements
+aliases:
+  gnome7: https://gnome7.codethink.co.uk/
+  gnomesdk: https://sdk.gnome.org/
+  project_dir: file://{project_dir}
+options:
+  linux:
+    type: bool
+    description: Whether to expect a linux platform
+    default: True
+split-rules:
+  test:
+    - |
+      /tests/*
\ No newline at end of file