diff --git a/extra_fixtures/extension_configs/extension/good_param/config.json b/extra_fixtures/extension_configs/extensions/good_param/config.json
similarity index 100%
rename from extra_fixtures/extension_configs/extension/good_param/config.json
rename to extra_fixtures/extension_configs/extensions/good_param/config.json
diff --git a/extra_fixtures/extension_configs/extension/no_config/keep b/extra_fixtures/extension_configs/extensions/no_config/keep
similarity index 100%
rename from extra_fixtures/extension_configs/extension/no_config/keep
rename to extra_fixtures/extension_configs/extensions/no_config/keep
diff --git a/extra_fixtures/extension_configs/extension/not_json/config.json b/extra_fixtures/extension_configs/extensions/not_json/config.json
similarity index 100%
rename from extra_fixtures/extension_configs/extension/not_json/config.json
rename to extra_fixtures/extension_configs/extensions/not_json/config.json
diff --git a/extra_fixtures/extension_configs/extensions/not_json_object/config.json b/extra_fixtures/extension_configs/extensions/not_json_object/config.json
new file mode 100644
index 00000000..d70f61cb
--- /dev/null
+++ b/extra_fixtures/extension_configs/extensions/not_json_object/config.json
@@ -0,0 +1,4 @@
+[
+    "This is not a JSON object",
+    "(it is an array, which is not legal for extension config.json)"
+]
diff --git a/ocfl/layout.py b/ocfl/layout.py
index 8cbce0e5..0d500686 100644
--- a/ocfl/layout.py
+++ b/ocfl/layout.py
@@ -1,8 +1,10 @@
 """Handle different storage layouts.
 
-OCFL Storage roots require a deterministic mapping from the object identifiers
-to the path within the storage root. This layout must be consistent across all
-objects in the storage root. It often includes two components:
+OCFL Storage Roots require a deterministic mapping from the object identifiers
+to the path within the storage root. (It is not required that one can deduce the
+object id from the path, as is the case with a hashed layout for example). The
+layout must be consistent across all objects in the storage root. It often
+includes two components:
 
 1) A mapping from the identifier to a set of directory names to create a path
 where objects are somewhatevenly distributed and will not end up with too many
@@ -12,7 +14,7 @@
 
 2) A final directory name that may be a more complete representation of the
 object id, by typically with at least some cleaning for safety. Some layouts
-use just the remainder of a hash however. Obviously algorithms but avoid
+use just the remainder of a hash however. Obviously algorithms must avoid
 collision in this part within a given path.
 
 See: https://ocfl.io/1.1/spec/#root-hierarchies
@@ -98,13 +100,19 @@ def read_layout_params(self, root_fs=None, params_required=False):
           root_fs: the storage root fs object
           params_required: if True then throw exception for params file not present
 
-        Returns None
+        Returns None, sets instance data in accord with the configuration using
+        the methods in self.PARAMS to parse for each key.
+
+        Raises LayoutException if the config can't be read or if required by
+        params_required but not present.
         """
         config = None
+        print("Reading extension config file %s" % (self.config_file))
         if root_fs.exists(self.config_file):
             try:
                 with root_fs.open(self.config_file) as fh:
                     config = json.load(fh)
+                    print("#### " + str(config))
             except Exception as e:
                 raise LayoutException("Storage root extension config file %s exists but can't be read/parsed (%s)" % (self.config_file, str(e)))
             if not isinstance(config, dict):
@@ -122,7 +130,7 @@ def check_and_set_layout_params(self, config, require_extension_name=True):
             require_extension_name: boolean, True by default. If set False then
                 the extensionName paramater is not required
 
-        For each parameter that is recognizedm, the appropriate check and set
+        For each parameter that is recognized, the appropriate check and set
         method in self.PARAMS is called. The methods set instance attributes.
         """
         # Check the extensionName if required and/or specified
@@ -139,6 +147,9 @@ def write_layout_params(self, root_fs=None):
         """Write the config.json file with layout parameters if need for this layout.
 
         Does nothing if there is no config.json content defined for this layout.
+
+        Raises a LayoutException if there is an error trying to write the config.json
+        file, including if one already exists.
         """
         config = self.config
         if config is None:
diff --git a/requirements.txt b/requirements.txt
index e4f45403..f12c9b46 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,3 +6,4 @@ fs_s3fs >= 1.1.1
 pairtree >= 0.8.1
 # Required for extras
 requests >= 2.20.0
+mock >= 5.1.0
diff --git a/setup.py b/setup.py
index e73a9bd4..5f261f6a 100644
--- a/setup.py
+++ b/setup.py
@@ -70,6 +70,9 @@ def run(self):
         'fs_s3fs>=1.1.1',
         'pairtree>=0.8.1'
     ],
+    tests_require=[
+        'mock>=5.1'
+    ],
     test_suite="tests",
     cmdclass={
         'coverage': Coverage
diff --git a/tests/test_layout.py b/tests/test_layout.py
index d9433f1e..97580653 100644
--- a/tests/test_layout.py
+++ b/tests/test_layout.py
@@ -44,7 +44,7 @@ def test_encodea_and_decode(self):
         self.assertEqual(layout.decode('http%3a%2f%2Fa.b.c'), 'http://a.b.c')
         self.assertRaises(LayoutException, layout.identifier_to_path, 'id')
 
-    def text_read_layout_params(self):
+    def test_read_layout_params(self):
         """Test read_layout_params."""
         root_fs = open_fs("extra_fixtures/extension_configs")
         layout = Layout()
@@ -54,14 +54,20 @@ def text_read_layout_params(self):
         def parse_param(value):
             layout.param = value
         layout.PARAMS = {"param": parse_param}
-        layout.read_layout_params(root_fs=root_fs)
+        layout.read_layout_params(root_fs=root_fs, params_required=True)
         self.assertEqual(layout.param, "yay!")
+        # No config file but none required
+        # Idoesn't do anything, nothing to check)
+        layout.NAME = "no_config"
+        layout.read_layout_params(root_fs=root_fs, params_required=False)
         # Error cases
         # No config file
         layout.NAME = "no_config"
-        self.assertRaises(LayoutException, layout.read_layout_params, root_fs=root_fs)
+        self.assertRaises(LayoutException, layout.read_layout_params, root_fs=root_fs, params_required=True)
         layout.NAME = "not_json"
         self.assertRaises(LayoutException, layout.read_layout_params, root_fs=root_fs)
+        layout.NAME = "not_json_object"
+        self.assertRaises(LayoutException, layout.read_layout_params, root_fs=root_fs)
 
     def test_check_and_set_layout_params(self):
         """Test check_and_set_layout_params."""