Allow for a nil value when mocking OS (#212)

As used in InSpec tests, if a nil is passed in when mocking an OS,
we should still properly create a fully-fledged Mock OS to prevent
further failures.

Signed-off-by: Adam Leff <adam@leff.co>

lib/train/transports/mock.rb

@@ -74,6 +74,9 @@ def uri
     end
 
     def mock_os(value = {})
+      # if a user passes a nil value, set to an empty hash so the merge still succeeds
+      value ||= {}
+
       os_params = { name: 'unknown', family: 'unknown', release: 'unknown', arch: 'unknown' }.merge(value)
       @os = OS.new(self, os_params)
     end

test/unit/transports/mock_test.rb

@@ -81,6 +81,40 @@
       connection.os.redhat?.must_equal true
       connection.os[:family].must_equal 'centos'
     end
+
+    it 'allows the setting of the name' do
+      connection.mock_os({ name: 'foo' })
+      connection.os[:name].must_equal 'foo'
+    end
+
+    it 'allows setting of the family' do
+      connection.mock_os({ family: 'foo' })
+      connection.os[:family].must_equal 'foo'
+    end
+
+    it 'allows setting of the release' do
+      connection.mock_os({ release: '1.2.3' })
+      connection.os[:release].must_equal '1.2.3'
+    end
+
+    it 'allows setting of the arch' do
+      connection.mock_os({ arch: 'amd123' })
+      connection.os[:arch].must_equal 'amd123'
+    end
+
+    it 'allow setting of multiple values' do
+      connection.mock_os({ name: 'foo', family: 'bar' })
+      connection.os[:name].must_equal 'foo'
+      connection.os[:family].must_equal 'bar'
+      connection.os[:arch].must_equal 'unknown'
+      connection.os[:release].must_equal 'unknown'
+    end
+
+    it 'properly handles a nil value' do
+      connection.mock_os(nil)
+      connection.os[:name].must_equal 'unknown'
+      connection.os[:family].must_equal 'unknown'
+    end
   end
 
   describe 'when accessing a mocked file' do