add test for new helpers

spec/helpers/date_time_helper_spec.rb

@@ -0,0 +1,37 @@
+require 'spec_helper'
+
+describe DateTimeHelper, type: :helper do
+
+  describe 'format_datetime' do
+    it 'returns nothing if there is no parameter' do
+      expect(format_datetime(nil)).to eq nil
+    end
+
+    it 'returns formatted string' do
+      datetime = Time.zone.local(2016, 05, 04, 11, 30)
+      expect(format_datetime(datetime)).to eq '2016-05-04 11:30'
+    end
+  end
+
+  describe 'show_time' do
+    it 'when length > 60' do
+      expect(show_time(67)).to eq '1 h 7 min'
+    end
+
+    it 'when length = 60' do
+      expect(show_time(60)).to eq '1 h'
+    end
+
+    it 'when length < 60' do
+      expect(show_time(58)).to eq '58 min'
+    end
+
+    it 'when length > 60 and is a decimal number' do
+      expect(show_time(68.3)).to eq '1 h 8 min'
+    end
+
+    it 'when length is nil' do
+      expect(show_time(nil)).to eq '0 h 0 min'
+    end
+  end
+end