diff --git a/.gitignore b/.gitignore
index 4e0819e..a2fe427 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@
 mkmf.log
 **/*.swp
 **/*.gem
+/rubyspec_temp/
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..072bbc6
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "spec/ruby_spec"]
+	path = spec/ruby_spec
+	url = https://github.com/ruby/spec
diff --git a/Gemfile b/Gemfile
index b806447..a9dfb0a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,3 +2,6 @@ source 'https://rubygems.org'
 
 # Specify your gem's dependencies in faster_path.gemspec
 gemspec
+
+# https://github.com/ruby/spec dependencies
+eval_gemfile File.expand_path('spec/ruby_spec/Gemfile', File.dirname(__FILE__))
diff --git a/README.md b/README.md
index f492bb9..3be48dd 100644
--- a/README.md
+++ b/README.md
@@ -116,7 +116,7 @@ And then execute:
 Or install it yourself as:
 
     $ gem install faster_path
-    
+
 **MAC USERS:** At the moment Mac users need to install the extension manualy.  Go to the gem directory and run `cargo build --release` .  There is an issue opened for this and I'm looking for people who have Macs to help on this.
 
 ## Usage
@@ -134,7 +134,7 @@ Current methods implemented:
 | `FasterPath.add_trailing_separator` | `Pathname#add_trailing_separator` | 46.8% |
 
 You may choose to use the methods directly, or scope change to rewrite behavior on the
-standard library with the included refinements, or even call a method to monkeypatch 
+standard library with the included refinements, or even call a method to monkeypatch
 everything everywhere.
 
 **Note:** `Pathname#chop_basename` in Ruby STDLIB has a bug with blank strings, that is the
@@ -169,6 +169,42 @@ Whenever feasible implement it in Rust.
 After checking out the repo, make sure you have Rust installed.  Then run `bundle && rake build_lib` .
 Then, run `rake test` to run the tests, and `rake bench` for benchmarks.
 
+### Building and running tests
+
+First, bundle the gem's development dependencies by running `bundle`.
+
+Then, build the rust code:
+
+```sh
+rake build_src
+```
+
+FasterPath is tested with [The Ruby Spec Suite](https://github.com/ruby/spec) to ensure it is compatible with the
+native implementation, and also has its own test suite testing its monkey-patching and refinements functionality.
+
+To run all the tests at once, simply run `rake`.
+To run all the ruby spec tests, run `mspec`.
+
+To run an individual test or benchmark from FasterPath's own suite:
+
+```sh
+# An individual test file:
+ruby -I lib:test test/benches/absolute_benchmark.rb
+# All tests:
+rake minitest
+```
+
+To run an individual ruby spec test, run `mspec` with a path relative to `spec/ruby_spec`, e.g.:
+
+```sh
+# A path to a file or a directory:
+mspec core/file/basename_spec.rb
+# Tests most relevant to FasterPath:
+mspec core/file library/pathname
+# All tests:
+mspec
+```
+
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/danielpclark/faster_path.
diff --git a/Rakefile b/Rakefile
index 304c1a1..d6cafce 100644
--- a/Rakefile
+++ b/Rakefile
@@ -27,12 +27,16 @@ task :build_lib => [:build_src, :clean_src] do
   puts "Completed build!"
 end
 
-Rake::TestTask.new(:test) do |t|
+Rake::TestTask.new(:minitest) do |t|
   t.libs << "test"
   t.libs << "lib"
   t.test_files = FileList['test/**/*_test.rb']
 end
 
+task :test => :minitest do |t|
+  exec 'mspec core/file library/pathname'
+end
+
 Rake::TestTask.new(:bench) do |t|
   t.libs = %w(lib test)
   t.pattern = 'test/**/*_benchmark.rb'
diff --git a/lib/faster_path/optional/monkeypatches.rb b/lib/faster_path/optional/monkeypatches.rb
index 58373fa..a210ec7 100644
--- a/lib/faster_path/optional/monkeypatches.rb
+++ b/lib/faster_path/optional/monkeypatches.rb
@@ -1,10 +1,12 @@
+require 'pathname'
+
 module FasterPath
   def self.sledgehammer_everything!
-    ::File.class_eval do
-      def basename(pth)
-        FasterPath.basename(pth)
-      end 
-    end 
+    ::File.module_eval do
+      def self.basename(pth, ext = '')
+        FasterPath.basename(pth, ext)
+      end
+    end
 
     ::Pathname.class_eval do
       def absolute?
diff --git a/lib/faster_path/optional/refinements.rb b/lib/faster_path/optional/refinements.rb
index d9056a3..a4bb3af 100644
--- a/lib/faster_path/optional/refinements.rb
+++ b/lib/faster_path/optional/refinements.rb
@@ -1,11 +1,11 @@
 module FasterPath
   module RefineFile
     refine File do
-      def basename(pth)
-        FasterPath.basename(pth)
+      def self.basename(pth, ext = '')
+        FasterPath.basename(pth, ext)
       end
     end
-  end 
+  end
 
   module RefinePathname
     refine Pathname do
diff --git a/spec/default.mspec b/spec/default.mspec
new file mode 100644
index 0000000..b8e3c6d
--- /dev/null
+++ b/spec/default.mspec
@@ -0,0 +1,8 @@
+load 'spec/ruby_spec/default.mspec'
+
+class MSpecScript
+  set :requires, ["-r#{File.expand_path('init', File.dirname(__FILE__))}"]
+  set :prefix, 'spec/ruby_spec'
+end
+
+MSpec.disable_feature :encoding
diff --git a/spec/init.rb b/spec/init.rb
new file mode 100644
index 0000000..afe0b11
--- /dev/null
+++ b/spec/init.rb
@@ -0,0 +1,5 @@
+ENV['BUNDLE_GEMFILE'] = File.expand_path('../Gemfile', File.dirname(__FILE__))
+$LOAD_PATH.unshift File.expand_path('../lib', File.dirname(__FILE__))
+require 'faster_path'
+require 'faster_path/optional/monkeypatches'
+FasterPath.sledgehammer_everything!
diff --git a/spec/ruby_spec b/spec/ruby_spec
new file mode 160000
index 0000000..8190a7c
--- /dev/null
+++ b/spec/ruby_spec
@@ -0,0 +1 @@
+Subproject commit 8190a7c915fbcf4776b99390418fe63fc6086c02
diff --git a/src/basename.rs b/src/basename.rs
index 7d69f89..8685219 100644
--- a/src/basename.rs
+++ b/src/basename.rs
@@ -30,15 +30,15 @@ fn it_chomps_strings_correctly(){
   assert_eq!(rubyish_basename(".ruby/ruby.rb.swp",".rb")       , "ruby.rb.swp");
   assert_eq!(rubyish_basename(".ruby/ruby.rb.swp",".swp")      , "ruby.rb");
   assert_eq!(rubyish_basename(".ruby/ruby.rb.swp",".*")        , "ruby.rb");
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp","")           , "asdf.rb.swp"); 
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".*")        , "asdf.rb"); 
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", "*")         , "asdf.rb.swp"); 
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".")         , "asdf.rb.swp"); 
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".*")        , "asdf.rb"); 
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".rb")       , "asdf.rb.swp"); 
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".swp")      , "asdf.rb"); 
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".sw")       , "asdf.rb.swp"); 
-  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".sw*")      , "asdf.rb.swp"); 
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp","")           , "asdf.rb.swp");
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".*")        , "asdf.rb");
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", "*")         , "asdf.rb.swp");
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".")         , "asdf.rb.swp");
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".*")        , "asdf.rb");
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".rb")       , "asdf.rb.swp");
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".swp")      , "asdf.rb");
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".sw")       , "asdf.rb.swp");
+  assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".sw*")      , "asdf.rb.swp");
   assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".rb.s*")    , "asdf.rb.swp");
   assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".s*")       , "asdf.rb.swp");
   assert_eq!(rubyish_basename("asdf/asdf.rb.swp", ".s**")      , "asdf.rb.swp");
@@ -55,32 +55,42 @@ fn it_chomps_strings_correctly(){
 
 #[no_mangle]
 pub extern fn basename(str_pth: *const c_char, comp_ext: *const c_char) -> *const c_char {
+  if str_pth.is_null() || comp_ext.is_null() {
+    return str_pth;
+  }
   let c_str1 = unsafe {
-    if str_pth.is_null(){
-      return str_pth;
-    } 
     CStr::from_ptr(str_pth)
   };
   let c_str2 = unsafe {
-    if comp_ext.is_null() {
-      return str_pth;
-    }
     CStr::from_ptr(comp_ext)
   };
+  // TODO: rb_raise on utf-8 errors
   let string         = str::from_utf8(c_str1.to_bytes()).unwrap();
   let globish_string = str::from_utf8(c_str2.to_bytes()).unwrap();
 
-  let result = if globish_string == ".*" {
-    let base = string.rsplit_terminator(MAIN_SEPARATOR).nth(0).unwrap_or("");
-    let index = base.rfind(".");
-    let (first, _) = base.split_at(index.unwrap());
-    first
+  let result = if string.is_empty() {
+    string
+  } else if globish_string == ".*" {
+    let base = extract_last_segment(string);
+    match base.rfind(".") {
+      Some(index) => &base[0..index],
+      _ => base,
+    }
   } else {
-    if &string[string.len()-globish_string.len()..] == globish_string {
-      &string[0..string.len()-globish_string.len()]
+    extract_last_segment(if &string[string.len() - globish_string.len()..] == globish_string {
+      &string[0..string.len() - globish_string.len()]
     } else {
       string
-    }.rsplit_terminator(MAIN_SEPARATOR).nth(0).unwrap_or("")
+    })
   };
   CString::new(result).unwrap().into_raw()
 }
+
+fn extract_last_segment(str: &str) -> &str {
+  let trimmed_str = str.trim_matches(MAIN_SEPARATOR);
+  if trimmed_str.is_empty() {
+    "/"
+  } else {
+    trimmed_str.rsplit_terminator(MAIN_SEPARATOR).nth(0).unwrap_or("")
+  }
+}