diff --git a/entrypoint.sh b/entrypoint.sh
index ef03418..f40db37 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -10,14 +10,14 @@ if !ENV["GITHUB_TOKEN"]
   exit(1)
 end
 
-if ARGV[0].empty?
+if ARGV[0]&.empty?
   puts "Missing message argument."
   exit(1)
 end
 
 commenter = Commenter.new(github: GitHub.new(env: ENV),
                           message: ARGV[0],
-                          check_for_dupes: ARGV[1],
+                          check_for_duplicates: ARGV[1],
                           duplicate_pattern: ARGV[2],
                           delete_previous_pattern: ARGV[3])
 
diff --git a/lib/commenter.rb b/lib/commenter.rb
index 73e526c..7acfa55 100644
--- a/lib/commenter.rb
+++ b/lib/commenter.rb
@@ -1,8 +1,8 @@
 class Commenter
-  def initialize(github:, message:, check_for_dupes: true, duplicate_pattern: nil, delete_previous_pattern: nil)
+  def initialize(github:, message:, check_for_duplicates: true, duplicate_pattern: nil, delete_previous_pattern: nil)
     @github = github
     @message = message
-    @block_duplicates = check_for_dupes.to_s.downcase.strip == "true"
+    @block_duplicates = check_for_duplicates.to_s.downcase.strip == "true"
     @duplicate_pattern = !duplicate_pattern.to_s.empty? && Regexp.new(duplicate_pattern)
     @delete_previous_pattern = !delete_previous_pattern.to_s.empty? && Regexp.new(delete_previous_pattern)
   end
@@ -15,16 +15,16 @@ def existing_duplicates?
     if @duplicate_pattern
       @github.comments.any? { |c| c["body"].match(/#{@duplicate_pattern}/) }
     else
-      @github.comments.any? { |c| c["body"] == message }
+      @github.comments.any? { |c| c["body"] == @message }
     end
   end
 
   def delete_matching_comments!
     return if !@delete_previous_pattern
 
-    comments.each do |comment|
-      if comment["body"].match(/#{@delete_prev_regex_msg}/)
-        @github.delete_comment(repo, comment["id"])
+    @github.comments.each do |comment|
+      if comment["body"].match(/#{@delete_previous_pattern}/)
+        @github.delete_comment(@github.repo, comment["id"])
       end
     end
   end
diff --git a/spec/commenter_spec.rb b/spec/commenter_spec.rb
new file mode 100644
index 0000000..c50bece
--- /dev/null
+++ b/spec/commenter_spec.rb
@@ -0,0 +1,85 @@
+  require "spec_helper"
+
+  RSpec.describe Commenter do
+  let(:github) do
+    spy("GitHub", comments: [
+      { "body" => "Oh, hi! I didn't see you there." },
+      { "body" => "Ah, that's just because of my invisibility powers." }
+    ],
+    delete_comment: true)
+  end
+
+  describe "#block_duplicates?" do
+    it "default" do
+      commenter = Commenter.new(github: github, message: "")
+      expect(commenter.block_duplicates?).to eq true
+    end
+
+    it "given true" do
+      commenter = Commenter.new(github: github, message: "", check_for_duplicates: true)
+      expect(commenter.block_duplicates?).to eq true
+    end
+
+    it "given 'true'" do
+      commenter = Commenter.new(github: github, message: "", check_for_duplicates: "true")
+      expect(commenter.block_duplicates?).to eq true
+    end
+
+    it "given 'false'" do
+      commenter = Commenter.new(github: github, message: "", check_for_duplicates: false)
+      expect(commenter.block_duplicates?).to eq false
+    end
+
+    it "given nil" do
+      commenter = Commenter.new(github: github, message: "", check_for_duplicates: nil)
+      expect(commenter.block_duplicates?).to eq false
+    end
+  end
+
+  describe "#existing_duplicates?" do
+    context "default/no pattern" do
+      it "finds exact comment" do
+        commenter = Commenter.new(github: github, message: "Ah, that's just because of my invisibility powers.")
+        expect(commenter.existing_duplicates?).to eq true
+      end
+
+      it "gives false when no matches" do
+        commenter = Commenter.new(github: github, message: "Today I will say a sentence never been said.")
+        expect(commenter.existing_duplicates?).to eq false
+      end
+    end
+
+    context "given pattern" do
+      it "finds matching comment" do
+        commenter = Commenter.new(github: github, message: "Is anyone listening?", duplicate_pattern: "invisibility powers")
+        expect(commenter.existing_duplicates?).to eq true
+      end
+
+      it "gives false when no matches" do
+        commenter = Commenter.new(github: github, message: "Is anyone listening?", duplicate_pattern: "common idioms")
+        expect(commenter.existing_duplicates?).to eq false
+      end
+    end
+  end
+
+  describe "#delete_matching_comments!" do
+    it "does nothing by default" do
+      commenter = Commenter.new(github: github, message: "")
+      expect(commenter.delete_matching_comments!).to eq nil
+      expect(github).to have_received(:delete_comment).exactly(0).times
+    end
+
+    it "does nothing given empty string" do
+      commenter = Commenter.new(github: github, message: "", delete_previous_pattern: "")
+      expect(commenter.delete_matching_comments!).to eq nil
+      expect(github).to have_received(:delete_comment).exactly(0).times
+    end
+
+    it "deletes matching comments given pattern" do
+      commenter = Commenter.new(github: github, message: "", delete_previous_pattern: "invisibility")
+      expect(commenter.delete_matching_comments!).to_not eq nil
+      expect(github).to have_received(:delete_comment).once
+    end
+  end
+
+  end
diff --git a/spec/github_spec.rb b/spec/github_spec.rb
index 41f994c..fc63f9c 100644
--- a/spec/github_spec.rb
+++ b/spec/github_spec.rb
@@ -1,4 +1,5 @@
 require "spec_helper"
+require "pry"
 
 RSpec.describe GitHub do
   describe "#pr_number" do
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 81f3d7a..208d196 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -2,7 +2,3 @@
 require "octokit"
 require_relative "../lib/github"
 require_relative "../lib/commenter"
-
-def stub_env(env)
-  stub_const("ENV", ENV.to_hash.merge(env))
-end