Implement condition DSL negated test prefix (no_*)

* Allow no_* to be used for every tests in condition DSL:
  condition { no_has_env :shell, '/bin/sh' };
* Modify Test constructor to accept negated: named argument, implement
  #negated? and #pass?;
* Rename #success? to #verify in all test classes.

spec/producer/core/test_spec.rb

@@ -14,6 +14,18 @@ module Producer::Core
       it 'assigns the arguments' do
         expect(test.instance_eval { @arguments }).to eq arguments
       end
+
+      it 'assigns negated as false by default' do
+        expect(test.instance_eval { @negated }).to be false
+      end
+
+      context 'when negated option is true' do
+        subject(:test) { Test.new(env, *arguments, negated: true) }
+
+        it 'assigns negated as true' do
+          expect(test.instance_eval { @negated }).to be true
+        end
+      end
     end
 
     describe '#env' do
@@ -27,5 +39,45 @@ module Producer::Core
         expect(test.arguments).to eq arguments
       end
     end
+
+    describe '#negated?' do
+      it 'returns false' do
+        expect(test.negated?).to be false
+      end
+
+      context 'when test is negated' do
+        subject(:test) { Test.new(env, *arguments, negated: true) }
+
+        it 'returns true' do
+          expect(test.negated?).to be true
+        end
+      end
+    end
+
+    describe '#pass?' do
+      it 'returns true when #verify is true' do
+        allow(test).to receive(:verify) { true }
+        expect(test.pass?).to be true
+      end
+
+      it 'returns false when #verify is false' do
+        allow(test).to receive(:verify) { false }
+        expect(test.pass?).to be false
+      end
+
+      context 'when test is negated' do
+        subject(:test) { Test.new(env, *arguments, negated: true) }
+
+        it 'returns false when #verify is true' do
+          allow(test).to receive(:verify) { true }
+          expect(test.pass?).to be false
+        end
+
+        it 'returns true when #verify is false' do
+          allow(test).to receive(:verify) { false }
+          expect(test.pass?).to be true
+        end
+      end
+    end
   end
 end