Include default style map when using custom style map

2 files changed, 20 insertions, 5 deletions

diff --git a/mammoth/options.py b/mammoth/options.py
index 4e4d5f1..a2e32b7 100644
--- a/mammoth/options.py
+++ b/mammoth/options.py
@@ -2,12 +2,9 @@ from . import style_reader, lists
 
 
 def read_options(options):
-    if options.get("style_map") is None:
-        style_map = _default_style_map
-    else:
-        style_map = _read_style_map(style_map)
+    custom_style_map = _read_style_map(options.get("style_map") or "")
     
-    options["style_map"] = style_map
+    options["style_map"] = custom_style_map + _default_style_map
     return options
 
 
diff --git a/tests/options_tests.py b/tests/options_tests.py
new file mode 100644
index 0000000..c646b12
--- /dev/null
+++ b/tests/options_tests.py
@@ -0,0 +1,18 @@
+from nose.tools import istest, assert_equal
+
+from mammoth import style_reader
+from mammoth.options import read_options, _default_style_map
+
+
+@istest
+def default_style_map_is_used_if_style_map_is_not_set():
+    assert_equal(_default_style_map, read_options({})["style_map"])
+
+
+@istest
+def custom_style_mappings_are_prepended_to_default_style_mappings():
+    style_map = read_options({
+        "style_map": "p.SectionTitle => h2"
+    })["style_map"]
+    assert_equal(style_reader.read_style("p.SectionTitle => h2"), style_map[0])
+    assert_equal(_default_style_map, style_map[1:])