diff --git a/.rspec b/.rspec
new file mode 100644
index 0000000..5f16476
--- /dev/null
+++ b/.rspec
@@ -0,0 +1,2 @@
+--color
+--format progress
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..b0c7645
--- /dev/null
+++ b/Gemfile
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+source 'https://rubygems.org'
+
+gem 'rspec'
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..7359464
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,18 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    diff-lcs (1.2.4)
+    rspec (2.14.1)
+      rspec-core (~> 2.14.0)
+      rspec-expectations (~> 2.14.0)
+      rspec-mocks (~> 2.14.0)
+    rspec-core (2.14.5)
+    rspec-expectations (2.14.3)
+      diff-lcs (>= 1.1.3, < 2.0)
+    rspec-mocks (2.14.3)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  rspec
diff --git a/lib/sudoku_validator.rb b/lib/sudoku_validator.rb
new file mode 100644
index 0000000..c292889
--- /dev/null
+++ b/lib/sudoku_validator.rb
@@ -0,0 +1,77 @@
+require 'Matrix'
+
+class SudokuValidator
+  def initialize(file=nil)
+    return if file.nil?
+
+    puzzle = []
+    open(file).each do |line|
+      row = line.gsub(/[|\-+]/, "")
+      unless row.strip.empty?
+        puzzle.push(row.split(' ').map{|x| x == '.' ? nil : x.to_i})
+      end
+    end
+
+    @puzzle = Matrix.rows(puzzle)
+  end
+
+  def valid?
+    return false if @puzzle.nil?
+    return validate(@puzzle)
+  end
+
+  def complete?
+    @puzzle.row_vectors.each do |row|
+      return false if row.include? nil
+    end
+    true
+  end
+
+  def validate(puzzle)
+    valid_puzzle?(puzzle) && valid_rows?(puzzle) && valid_columns?(puzzle) && valid_submatricies?(puzzle)
+  end
+
+  def valid_puzzle?(puzzle)
+    puzzle.square? && (puzzle.row_count % 3) == 0
+  end
+
+  def valid_rows?(puzzle)
+    puzzle.row_vectors.each do |row|
+      return false unless grouping_valid?(row)
+    end
+
+    true
+  end
+
+  def valid_columns?(puzzle)
+    puzzle.column_vectors.each do |column|
+      return false unless grouping_valid?(column)
+    end
+
+    true
+  end
+
+  def valid_submatricies?(puzzle)
+    (puzzle.row_count / 3).times do |row|
+      (puzzle.column_count / 3).times do |column|
+        subpuzzle = puzzle.minor(3*row..(3*row)+2, 3*column..(3*column)+2)
+        flattened = []
+        subpuzzle.row_vectors.each do |subrow|
+          flattened += subrow.to_a
+        end
+        return false unless grouping_valid?(flattened)
+      end
+    end
+
+    true
+  end
+
+  def grouping_valid?(set)
+    values = Hash.new(0)
+    set.each do |value|
+      values[value] += 1 unless value == nil
+    end
+
+    values.find{|k, v| v > 1 } == nil
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
new file mode 100644
index 0000000..dbc4f1a
--- /dev/null
+++ b/spec/spec_helper.rb
@@ -0,0 +1,17 @@
+# This file was generated by the `rspec --init` command. Conventionally, all
+# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
+# Require this file using `require "spec_helper"` to ensure that it is only
+# loaded once.
+#
+# See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  config.treat_symbols_as_metadata_keys_with_true_values = true
+  config.run_all_when_everything_filtered = true
+  config.filter_run :focus
+
+  # Run specs in random order to surface order dependencies. If you find an
+  # order dependency and want to debug it, you can fix the order by providing
+  # the seed, which is printed after each run.
+  #     --seed 1234
+  config.order = 'random'
+end
diff --git a/spec/sudoku_validator_spec.rb b/spec/sudoku_validator_spec.rb
new file mode 100644
index 0000000..f495a0a
--- /dev/null
+++ b/spec/sudoku_validator_spec.rb
@@ -0,0 +1,49 @@
+require 'sudoku_validator'
+
+describe SudokuValidator do
+  before (:each) do
+    @validator = SudokuValidator.new
+  end
+
+  it "has no duplicates in a row" do
+    validPuzzle = Matrix[[1,2,3],[nil,nil,nil],[nil,nil,nil]]
+    @validator.validate(validPuzzle).should be_true
+
+    invalidPuzzle = Matrix[[1,1,2],[nil,nil,nil],[nil,nil,nil]]
+    @validator.validate(invalidPuzzle).should be_false
+  end
+
+  it "has no duplicates in a column" do
+    validPuzzle = Matrix[[1,nil,nil],[2,nil,nil],[3,nil,nil]]
+    @validator.validate(validPuzzle).should be_true
+
+    invalidPuzzle = Matrix[[1,nil,nil], [1,nil,nil], [2,nil,nil]]
+    @validator.validate(invalidPuzzle).should be_false
+  end
+
+  it "has no duplicates in a sub-grid" do
+    validPuzzle = Matrix[[1,2,3],[4,5,6],[7,8,9]]
+    @validator.validate(validPuzzle).should be_true
+
+    invalidPuzzle = Matrix[[1,2,3],[4,5,6],[7,8,1]]
+    @validator.validate(invalidPuzzle).should be_false
+  end
+
+  it "validates files" do
+    vc = SudokuValidator.new("valid_complete.sudoku")
+    vc.valid?.should be_true
+    vc.complete?.should be_true
+
+    vi = SudokuValidator.new("valid_incomplete.sudoku")
+    vi.valid?.should be_true
+    vi.complete?.should be_false
+
+    ic = SudokuValidator.new("invalid_complete.sudoku")
+    ic.valid?.should be_false
+    ic.complete?.should be_true
+
+    ii = SudokuValidator.new("invalid_incomplete.sudoku")
+    ii.valid?.should be_false
+    ii.complete?.should be_false
+  end
+end
diff --git a/sudoku-validator b/sudoku-validator
new file mode 100755
index 0000000..d379acd
--- /dev/null
+++ b/sudoku-validator
@@ -0,0 +1,5 @@
+#!/usr/bin/env ruby
+require_relative 'lib/sudoku_validator'
+
+validator = SudokuValidator.new(ARGV[0])
+puts "This sudoku is #{!validator.valid? ? "in" : ""}valid#{validator.valid? && !validator.complete? ? ", but incomplete" : ""}."