Fix off by one error in metadata tests [skip ci]

Author: adamtheturtle

src/mock_vws/_validators.py

@@ -906,7 +906,8 @@ def validate_metadata_size(
         return wrapped(*args, **kwargs)
     decoded = base64.b64decode(application_metadata)
 
-    if len(decoded) <= 1024 * 1024:
+    max_metadata_bytes = 1024 * 1024 - 1
+    if len(decoded) <= max_metadata_bytes:
         return wrapped(*args, **kwargs)
 
     context.status_code = codes.UNPROCESSABLE_ENTITY

tests/mock_vws/test_add_target.py

@@ -645,11 +645,13 @@ class TestApplicationMetadata:
     Tests for the application metadata parameter.
     """
 
+    _MAX_METADATA_BYTES = 1024 * 1024 - 1
+
     @pytest.mark.parametrize(
         'metadata',
         [
             b'a',
-            b'a' * (1024 * 1024),
+            b'a' * _MAX_METADATA_BYTES,
         ],
         ids=['Short', 'Max length'],
     )
@@ -781,12 +783,12 @@ def test_metadata_too_large(
         png_rgb: io.BytesIO,
     ) -> None:
         """
-        A base64 encoded string of up to 1024 * 1024 bytes is valid application
-        metadata.
+        A base64 encoded string of greater than 1024 * 1024 bytes is too large
+        for application metadata.
         """
         image_data = png_rgb.read()
         image_data_encoded = base64.b64encode(image_data).decode('ascii')
-        metadata = b'a' * (1024 * 1024 + 1)
+        metadata = b'a' * (self._MAX_METADATA_BYTES + 1)
         metadata_encoded = base64.b64encode(metadata).decode('ascii')
 
         data = {