Move unit tests to their own sub-dir in tests

tests/unit_tests/mock_stitching/mock-stitch.py

@@ -0,0 +1,22 @@
+"""CLI script used for testing subprocess calls that should go to openflexure-stitch."""
+
+import sys
+import time
+
+
+def main():
+    """Echo command-line arguments with a short delay between each."""
+    input_arguments = sys.argv[1:]
+    for arg in input_arguments:
+        # This is used to check we catch errors correctly.
+        if arg == "ERROR":
+            raise RuntimeError("I was told to do this.")
+        if arg == "HANG":
+            # Rather than hang, just sleep for 10s:
+            time.sleep(10)
+        print(arg, flush=True)
+        time.sleep(0.2)
+
+
+if __name__ == "__main__":
+    main()