diff --git a/.gitignore b/.gitignore
index e74bf5c..94739bb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,6 @@
+# ignore test directories
+spec/index_dir/*
+
 # rcov generated
 coverage
 
diff --git a/lib/polecat/index.rb b/lib/polecat/index.rb
index 9311b4a..a906c04 100644
--- a/lib/polecat/index.rb
+++ b/lib/polecat/index.rb
@@ -16,7 +16,7 @@ class Polecat
 
     # returns true, if it has an index
     def index_dir?
-      false
+      File.exists?(@path + '/index.txt')
     end
 
     def write term
diff --git a/spec/index_spec.rb b/spec/index_spec.rb
index a05139a..71708f5 100644
--- a/spec/index_spec.rb
+++ b/spec/index_spec.rb
@@ -29,7 +29,11 @@ describe "Index" do
       i.index_dir?.should == false
     end
 
-    it "returns true, if the directory contains an index"
+    it "returns true, if the directory contains an index" do
+      i = Polecat::Index.new @path
+      i.write 'foo'
+      i.index_dir?.should == true
+    end
   end
 
   describe "#write" do
@@ -63,5 +67,12 @@ describe "Index" do
       i.write "foo"
       i.search("foo").should == 0
     end
+
+    it "returns nil, when no match was found" do
+      i = Polecat::Index.new @path
+      i.write "foo"
+      i.write "bar"
+      i.search("baz").should == nil
+    end
   end
 end