1 files changed, 21 insertions, 2 deletions
diff --git a/tests/docx/files_tests.py b/tests/docx/files_tests.py
index c1e15dc..56dc69a 100644
--- a/tests/docx/files_tests.py
+++ b/tests/docx/files_tests.py
@@ -1,7 +1,7 @@
 from nose.tools import istest, assert_equal
 
-from mammoth.docx.files import Files
-from ..testing import test_path
+from mammoth.docx.files import Files, InvalidFileReferenceError
+from ..testing import test_path, assert_raises
 
 
 @istest
@@ -23,3 +23,22 @@ def can_open_files_with_relative_uri():
         assert_equal(bytes, type(contents))
         with open(test_path("tiny-picture.png"), "rb") as source_file:
             assert_equal(source_file.read(), contents)
+
+
+@istest
+def error_is_raised_if_relative_uri_cannot_be_opened():
+    files = Files("/tmp")
+    error = assert_raises(InvalidFileReferenceError, lambda: files.open("not-a-real-file.png"))
+    expected_message = (
+        "could not open external image: 'not-a-real-file.png' (document directory: '/tmp')\n" +
+        "[Errno 2] No such file or directory: '/tmp/not-a-real-file.png'"
+    )
+    assert_equal(expected_message, str(error))
+
+
+@istest
+def error_is_raised_if_file_uri_cannot_be_opened():
+    files = Files("/tmp")
+    error = assert_raises(InvalidFileReferenceError, lambda: files.open("file:///not-a-real-file.png"))
+    expected_message = "could not open external image: 'file:///not-a-real-file.png' (document directory: '/tmp')\n"
+    assert str(error).startswith(expected_message)