Test workflow

test/verify_generated_script.py

@@ -0,0 +1,59 @@
+"""Checks that an exported script looks right and produced a real image.
+
+Run after e2e_save_as_script.py has downloaded a script and that script has been
+executed, to confirm the export reflects the workflow rather than just being
+syntactically valid Python.
+"""
+
+import argparse
+import ast
+import os
+import sys
+
+PNG_MAGIC = b"\x89PNG\r\n\x1a\n"
+
+
+def check_script(path, expected):
+    with open(path, encoding="utf-8") as f:
+        source = f.read()
+
+    # A truncated or error-page download would fail to parse
+    try:
+        ast.parse(source)
+    except SyntaxError as e:
+        raise SystemExit(f"Exported script is not valid Python: {e}")
+
+    missing = [node for node in expected if node not in source]
+    if missing:
+        raise SystemExit(
+            f"Exported script does not reference {missing}; the workflow may not have "
+            "loaded before it was exported."
+        )
+
+    print(f"{path}: valid Python, references {', '.join(expected)}")
+
+
+def check_image(path):
+    if not os.path.isfile(path):
+        raise SystemExit(f"The generated script did not produce {path}")
+    with open(path, "rb") as f:
+        header = f.read(len(PNG_MAGIC))
+    if header != PNG_MAGIC:
+        raise SystemExit(f"{path} is not a PNG (got {header!r})")
+    print(f"{path}: valid PNG, {os.path.getsize(path)} bytes")
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--script", required=True, help="The exported Python script")
+    parser.add_argument("--expect", nargs="*", default=[], help="Node types the script must reference")
+    parser.add_argument("--image", default=None, help="PNG the script was expected to write")
+    args = parser.parse_args()
+
+    check_script(args.script, args.expect)
+    if args.image:
+        check_image(args.image)
+
+
+if __name__ == "__main__":
+    main()