add test for #42

features/multiple_files.feature

+Feature: BibTeX
+  As a scholar who likes to blog
+  I want to publish my BibTeX bibliography on my website
+  Based on multiple BibTeX files
+
+
+  Scenario: Multiple bibliography files
+    Given I have a scholar configuration with:
+      | key    | value             |
+      | source | ./_bibliography   |
+    And I have a "_bibliography" directory
+    And I have a file "_bibliography/references1.bib":
+      """
+      @book{ruby,
+        title     = {The Ruby Programming Language},
+        author    = {Flanagan, David and Matsumoto, Yukihiro},
+        year      = {2008},
+        publisher = {O'Reilly Media}
+      }
+      """
+    And I have a file "_bibliography/references2.bib":
+      """
+      @book{microscope,
+        title     = {Ruby Under a Microscope},
+        author    = {Pat Shaughnessy},
+        year      = {2013},
+        publisher = {No Starch Press}
+      }
+      """
+    And I have a page "scholar.html":
+      """
+      ---
+      ---
+      {% bibliography -f references1 -f references2 %}
+      """
+    When I run jekyll
+    Then the _site directory should exist
+    And the "_site/scholar.html" file should exist
+    And I should see "<i>The Ruby Programming Language</i>" in "_site/scholar.html"
+    And I should see "<i>Ruby Under a Microscope</i>" in "_site/scholar.html"
+