Improve test coverage for configuration (#691)

* Improve test coverage for configuration

* Check that set? returns false if value is nil

spec/lib/mina/configuration_spec.rb

@@ -26,6 +26,44 @@
       expect(key).to eq 'env'
       ENV['key'] = nil
     end
+
+    it "returns nil if a default value isn't provided" do
+      expect(config.fetch(:key)).to eq(nil)
+    end
+  end
+
+  describe '#remove' do
+    context 'when key exists' do
+      before do
+        config.set(:key, :value)
+      end
+
+      it 'removes the key' do
+        expect(config.set?(:key)).to eq(true)
+
+        config.remove(:key)
+
+        expect(config.set?(:key)).to eq(false)
+      end
+
+      it 'returns key value' do
+        expect(config.remove(:key)).to eq(:value)
+      end
+    end
+
+    context "when key doesn't exist" do
+      it "doesn't do anything" do
+        expect(config.set?(:key)).to eq(false)
+
+        config.remove(:key)
+
+        expect(config.set?(:key)).to eq(false)
+      end
+
+      it 'returns nil' do
+        expect(config.remove(:key)).to eq(nil)
+      end
+    end
   end
 
   describe '#set?' do
@@ -34,6 +72,11 @@
       expect(config.set?(:key)).to be true
     end
 
+    it 'returns false if key is set with nil value' do
+      config.set(:key, nil)
+      expect(config.set?(:key)).to be false
+    end
+
     it 'returns false if key is not set' do
       expect(config.set?(:key)).to be false
     end
@@ -51,6 +94,20 @@
     end
   end
 
+  describe '#reset!' do
+    before do
+      config.set(:key, :value)
+    end
+
+    it 'cleans all variables' do
+      expect(config.variables).not_to be_empty
+
+      config.reset!
+
+      expect(config.variables).to be_empty
+    end
+  end
+
   describe Mina::Configuration::DSL do
     let(:host_class) { Class.new { include Mina::Configuration::DSL } }
     let(:host) { host_class.new }