add missing tests for postgresql_conf provider

spec/unit/provider/postgresql_conf/ruby_spec.rb

@@ -7,6 +7,54 @@
   let(:resource) { Puppet::Type.type(:postgresql_conf).new(name: 'foo', value: 'bar') }
   let(:provider) { resource.provider }
 
+  # rubocop:disable RSpec/ReceiveMessages
+  before(:each) do
+    allow(provider).to receive(:file_path).and_return('/tmp/foo')
+    allow(provider).to receive(:read_file).and_return('foo = bar')
+    allow(provider).to receive(:write_file).and_return(true)
+  end
+  # rubocop:enable RSpec/ReceiveMessages
+
+  it 'has a method parse_config' do
+    expect(provider).to respond_to(:parse_config)
+  end
+
+  it 'has a method delete_header' do
+    expect(provider).to respond_to(:delete_header)
+  end
+
+  it 'has a method add_header' do
+    expect(provider).to respond_to(:add_header)
+  end
+
+  it 'has a method exists?' do
+    expect(provider).to respond_to(:exists?)
+  end
+
+  it 'has a method create' do
+    expect(provider).to respond_to(:create)
+  end
+
+  it 'has a method destroy' do
+    expect(provider).to respond_to(:destroy)
+  end
+
+  it 'has a method value' do
+    expect(provider).to respond_to(:value)
+  end
+
+  it 'has a method value=' do
+    expect(provider).to respond_to(:value=)
+  end
+
+  it 'has a method comment' do
+    expect(provider).to respond_to(:comment)
+  end
+
+  it 'has a method comment=' do
+    expect(provider).to respond_to(:comment=)
+  end
+
   it 'is an instance of the Provider Ruby' do
     expect(provider).to be_an_instance_of Puppet::Type::Postgresql_conf::ProviderRuby
   end