diff --git a/lib/strict_periods/period_pickers/week_picker.rb b/lib/strict_periods/period_pickers/week_picker.rb
index a720534..1ad3bb6 100644
--- a/lib/strict_periods/period_pickers/week_picker.rb
+++ b/lib/strict_periods/period_pickers/week_picker.rb
@@ -11,7 +11,7 @@ def initialize(anchor: nil, past_only: true)
         @steps     = 0
         @anchor    = anchor
         @past_only = past_only
-        raise ArgumentError if @anchor.nil?
+        raise ArgumentError if @anchor.nil? || !@anchor.is_a?(Time)
 
         _offset_anchor
       end
diff --git a/spec/lib/period_pickers/week_picker_spec.rb b/spec/lib/period_pickers/week_picker_spec.rb
index 7a99dc0..d8ac92f 100644
--- a/spec/lib/period_pickers/week_picker_spec.rb
+++ b/spec/lib/period_pickers/week_picker_spec.rb
@@ -3,6 +3,120 @@
 require 'time'
 
 describe StrictPeriods::PeriodPickers::WeekPicker do
-  describe "#new", pending => true do
+
+	let(:anchor) { Time.utc(2016,3,7) }
+	let(:week_picker) { StrictPeriods::PeriodPickers::WeekPicker.new(anchor: anchor) }
+
+  describe "#new" do
+  	context "when a valid anchor date is provided" do
+      it "accepts anchor date formatted as '%Y-%m-%d' string" do
+        expect(week_picker.anchor).to be_truthy
+        expect(week_picker.anchor).to be_an_instance_of Time
+        expect(week_picker.anchor).to eq Time.utc(2016,3,7)
+        expect(week_picker.instance_variable_get(:@steps)).to eq 0
+      end
+    end
+
+    context "when no anchor is provided at all" do
+    	let(:anchor) { nil }
+      it { expect{ week_picker }.to raise_error ArgumentError }
+    end
+
+    context "when an invalid anchor is provided" do
+      let(:anchor) { "INVALID" }
+      it { expect{ week_picker }.to raise_error ArgumentError }
+    end
+
+    context "when past_only is not provided" do 
+    	it { expect(week_picker.past_only).to eq true }
+    end
+
+    context "when past_only is provided" do 
+    	let(:week_picker) { StrictPeriods::PeriodPickers::WeekPicker.new(anchor: anchor, past_only: false) }
+    	it { expect(week_picker.past_only).to eq false }
+    end
+  end
+
+  describe "#operands" do
+  	let(:number_of_weeks) { 2 }
+  	context "when using minus operand" do
+  		before do
+  			week_picker - number_of_weeks
+  		end
+  		it { expect(week_picker.anchor).to eq Time.utc(2016,2,22) }
+  		it { expect(week_picker.instance_variable_get(:@steps)).to eq -number_of_weeks }
+
+  		context "_offset_anchor should be the same" do
+		  	before do
+		  		week_picker.send(:_offset_anchor)
+		  	end
+		  	it { expect(week_picker.instance_variable_get(:@offset)).to eq 60*60*24*(7 - 1)}
+		  end
+  	end
+
+  	context "when using plus operand" do
+  		before do
+  			week_picker + number_of_weeks
+  		end
+  		it { expect(week_picker.anchor).to eq Time.utc(2016,3,21) }
+  		it { expect(week_picker.instance_variable_get(:@steps)).to eq number_of_weeks }
+
+  		context "_offset_anchor should be the same" do
+		  	before do
+		  		week_picker.send(:_offset_anchor)
+		  	end
+		  	it { expect(week_picker.instance_variable_get(:@offset)).to eq 60*60*24*(7 - 1)}
+		  end
+  	end
+  end
+
+  describe "#reset!" do
+  	before do
+  		week_picker.send(:reset!)
+  	end
+  	it { expect(week_picker.instance_variable_get(:@offset)).to eq 60*60*24*(7 - 1)}
+  	it { expect(week_picker.instance_variable_get(:@steps)).to eq 0 }
+  end
+
+  describe "_offset_anchor" do
+  	before do
+  		week_picker.send(:_offset_anchor)
+  	end
+  	it { expect(week_picker.instance_variable_get(:@offset)).to eq 60*60*24*(7 - 1)}
+  end
+
+  describe "_reset_steps" do
+  	let(:number_of_weeks) { 2 }
+
+  	context "when no action was done" do
+  		before do
+	  		week_picker.send(:_reset_steps)
+	  	end
+  		it { expect(week_picker.instance_variable_get(:@steps)).to eq 0 }
+  	end
+
+  	context "when weeks was subtracted" do
+  		before do
+  			week_picker - number_of_weeks
+	  		week_picker.send(:_reset_steps)
+	  	end
+  		it { expect(week_picker.instance_variable_get(:@steps)).to eq 0 }
+  	end
+
+  	context "when weeks was added" do
+  		before do
+  			week_picker + number_of_weeks
+	  		week_picker.send(:_reset_steps)
+	  	end
+  		it { expect(week_picker.instance_variable_get(:@steps)).to eq 0 }
+  	end
+  end
+
+  describe "_reset_offset" do
+  	before do
+  		week_picker.send(:_reset_offset)
+	  		week_picker.send(:_reset_steps)
+  	end
+  	it { expect(week_picker.instance_variable_get(:@offset)).to eq 60*60*24*(7 - 1)}
   end
 end
diff --git a/spec/lib/strict_period_spec.rb b/spec/lib/strict_period_spec.rb
index 27a671a..3c27bce 100644
--- a/spec/lib/strict_period_spec.rb
+++ b/spec/lib/strict_period_spec.rb
@@ -15,7 +15,7 @@
       it "accepts anchor date formatted as '%Y-%m-%d' string" do
         expect(strict_period.anchor).to be_truthy
         expect(strict_period.anchor).to be_an_instance_of Time
-        expect(strict_period.anchor.strftime('%Y-%m-%d')).to eq now.strftime('%Y-%m-%d')
+        expect(strict_period.anchor.strftime('%Y-%m-%d')).to eq Time.utc(2016,3,7).strftime('%Y-%m-%d')
       end
     end
 
@@ -32,6 +32,15 @@
 
       it { expect{ strict_period }.to raise_error ArgumentError }
     end
+
+    context "when past_only is not provided" do 
+      it { expect(strict_period.past_only).to eq true }
+    end
+
+    context "when past_only is provided" do 
+      let(:strict_period) { described_class.new(anchor: anchor, past_only: false) }
+      it { expect(strict_period.past_only).to eq false }
+    end
   end
 
   describe "#_anchor_at" do
@@ -74,9 +83,52 @@
     end
   end
 
-  describe "#previous_weeks", pending => true do
+  describe "#previous_weeks" do
+    let(:anchor) { Time.utc(2015,3,7).strftime('%Y-%m-%d') }
+    let(:number_of_weeks) { 2 }
+
+    context "when number_of_weeks value is not provided" do
+      it { expect(strict_period.previous_weeks).to be_kind_of(Array) }
+      it { expect(strict_period.previous_weeks).to eq [["2015-02-23", "2015-03-01"]] }
+      it { expect(Time.parse(strict_period.previous_weeks[0][0]).monday?).to eq true }
+      it { expect(Time.parse(strict_period.previous_weeks[0][1]).sunday?).to eq true }
+    end
+
+    context "when number_of_weeks value is provided" do
+      it { expect(strict_period.previous_weeks).to be_kind_of(Array) }
+      it { expect(strict_period.previous_weeks(number_of_weeks)).to eq [["2015-02-16", "2015-02-22"],["2015-02-23", "2015-03-01"]] }
+      it { expect(Time.parse(strict_period.previous_weeks(number_of_weeks)[0][0]).monday?).to eq true }
+      it { expect(Time.parse(strict_period.previous_weeks(number_of_weeks)[0][1]).sunday?).to eq true }
+      it { expect(Time.parse(strict_period.previous_weeks(number_of_weeks)[1][0]).monday?).to eq true }
+      it { expect(Time.parse(strict_period.previous_weeks(number_of_weeks)[1][1]).sunday?).to eq true }
+    end
   end
 
-  describe "#next_weeks", pending => true do
+  describe "#next_weeks" do
+    context "when next weeks are in the future" do
+      it { expect(strict_period.next_weeks).to be_kind_of(Array) }
+      it { expect(strict_period.next_weeks).to eq [] }
+    end
+
+    context "when next weeks are in the past" do
+      let(:anchor) { Time.utc(2015,3,7).strftime('%Y-%m-%d') }
+      let(:number_of_weeks) { 2 }
+
+      context "when number_of_weeks value is not provided" do
+        it { expect(strict_period.next_weeks).to be_kind_of(Array) }
+        it { expect(strict_period.next_weeks).to eq [["2015-03-09", "2015-03-15"]] }
+        it { expect(Time.parse(strict_period.next_weeks[0][0]).monday?).to eq true }
+        it { expect(Time.parse(strict_period.next_weeks[0][1]).sunday?).to eq true }
+      end
+
+      context "when number_of_weeks value is provided" do
+        it { expect(strict_period.next_weeks(number_of_weeks)).to be_kind_of(Array) }
+        it { expect(strict_period.next_weeks(number_of_weeks)).to eq [["2015-03-09", "2015-03-15"],["2015-03-16", "2015-03-22"]] }
+        it { expect(Time.parse(strict_period.next_weeks(number_of_weeks)[0][0]).monday?).to eq true }
+        it { expect(Time.parse(strict_period.next_weeks(number_of_weeks)[0][1]).sunday?).to eq true }
+        it { expect(Time.parse(strict_period.next_weeks(number_of_weeks)[1][0]).monday?).to eq true }
+        it { expect(Time.parse(strict_period.next_weeks(number_of_weeks)[1][1]).sunday?).to eq true }
+      end
+    end
   end
 end