diff --git a/spec/workflow/engine_spec.rb b/spec/workflow/engine_spec.rb
index 2d9225c8..184bbe91 100644
--- a/spec/workflow/engine_spec.rb
+++ b/spec/workflow/engine_spec.rb
@@ -119,6 +119,65 @@ module Kuroko2::Workflow
         end
       end
 
+      context 'with parallel_fork' do
+        let!(:definition) do
+          create(:job_definition_with_instances, script: <<-EOF.strip_heredoc)
+            env: GLOBAL_ENV=g
+            parallel_fork: 3
+              noop: noop1
+              noop: noop2
+          EOF
+        end
+
+        specify do
+          subject.process(token)
+          expect(token.path).to eq '/0-env'
+          subject.process(token)
+          expect(token.path).to eq '/1-parallel_fork'
+
+          subject.process(token)
+          expect(token.children.size).to eq 3
+
+          parallel_tokens = token.children
+          subject.process_all
+
+          parallel_tokens.each(&:reload)
+          expect(token.path).to eq '/1-parallel_fork'
+          expect(parallel_tokens.map(&:path)).to all(eq('/0-sequence'))
+
+          subject.process_all
+          parallel_tokens.each(&:reload)
+          expect(token.path).to eq '/1-parallel_fork'
+          expect(parallel_tokens.map(&:path)).to all(eq('/0-sequence/0-noop'))
+          expect(parallel_tokens.map(&:status_name)).to all(eq('working'))
+          expect(parallel_tokens.map{ |token| token.context['ENV']['KUROKO2_PARALLEL_FORK_SIZE'] }).to all(eq('3'))
+          expect(parallel_tokens.map{ |token| token.context['ENV']['GLOBAL_ENV'] }).to all(eq('g'))
+          expect(parallel_tokens[0].context['ENV']['KUROKO2_PARALLEL_FORK_INDEX']).to eq('0')
+          expect(parallel_tokens[1].context['ENV']['KUROKO2_PARALLEL_FORK_INDEX']).to eq('1')
+          expect(parallel_tokens[2].context['ENV']['KUROKO2_PARALLEL_FORK_INDEX']).to eq('2')
+
+          subject.process_all
+          parallel_tokens.each(&:reload)
+          expect(token.path).to eq '/1-parallel_fork'
+          expect(parallel_tokens.map(&:path)).to all(eq('/0-sequence/1-noop'))
+          expect(parallel_tokens.map(&:status_name)).to all(eq('working'))
+          expect(parallel_tokens.map{ |token| token.context['ENV']['KUROKO2_PARALLEL_FORK_SIZE'] }).to all(eq('3'))
+          expect(parallel_tokens.map{ |token| token.context['ENV']['GLOBAL_ENV'] }).to all(eq('g'))
+          expect(parallel_tokens[0].context['ENV']['KUROKO2_PARALLEL_FORK_INDEX']).to eq('0')
+          expect(parallel_tokens[1].context['ENV']['KUROKO2_PARALLEL_FORK_INDEX']).to eq('1')
+          expect(parallel_tokens[2].context['ENV']['KUROKO2_PARALLEL_FORK_INDEX']).to eq('2')
+
+          subject.process_all
+          parallel_tokens.each(&:reload)
+          expect(token.path).to eq '/1-parallel_fork'
+          expect(parallel_tokens.map(&:path)).to all(eq('/0-sequence/1-noop'))
+          expect(parallel_tokens.map(&:status_name)).to all(eq('finished'))
+
+          subject.process_all
+          expect(Kuroko2::Token.all.count).to eq 0
+        end
+      end
+
       context 'retry' do
         let!(:definition) do
           create(:job_definition_with_instances, script: <<-EOF.strip_heredoc)
diff --git a/spec/workflow/task/parallel_fork_spec.rb b/spec/workflow/task/parallel_fork_spec.rb
index 1cd638e2..62749367 100644
--- a/spec/workflow/task/parallel_fork_spec.rb
+++ b/spec/workflow/task/parallel_fork_spec.rb
@@ -5,16 +5,53 @@ module Kuroko2::Workflow::Task
     let(:node) { Kuroko2::Workflow::ScriptParser.new(token.script).parse.find(token.path) }
     let(:definition) { create(:job_definition) }
     let(:instance) { create(:job_instance, job_definition: definition) }
+    let(:script) do
+      <<-EOF.strip_heredoc
+        parallel_fork: 2
+          noop:
+      EOF
+    end
 
     let(:token) do
-      Kuroko2::Token.create(uuid: SecureRandom.uuid, path: '/0-fork', job_definition: definition, job_instance: instance, script: <<-EOF)
-parallel_fork: 2
-  noop:
-      EOF
+      Kuroko2::Token.create(uuid: SecureRandom.uuid, path: '/0-fork', job_definition: definition, job_instance: instance, script: script)
+    end
+
+    let(:task) { ParallelFork.new(node, token) }
+
+    describe '#validate' do
+      context 'with valid script format' do
+        it 'passes validation' do
+          expect{ task.validate }.not_to raise_error
+        end
+      end
+
+      context 'with invalid option' do
+        let(:script) do
+          <<-EOF.strip_heredoc
+            parallel_fork: B
+              noop:
+          EOF
+        end
+
+        it 'raises AssertionError' do
+          expect{ task.validate }.to raise_error(Kuroko2::Workflow::AssertionError)
+        end
+      end
+
+      context 'with invalid script format' do
+        let(:script) do
+          <<-EOF.strip_heredoc
+            parallel_fork: 100
+          EOF
+        end
+
+        it 'raises AssertionError' do
+          expect{ task.validate }.to raise_error(Kuroko2::Workflow::AssertionError)
+        end
+      end
     end
 
     describe '#execute' do
-      subject(:task) { ParallelFork.new(node, token) }
       let(:children) { token.children }
 
       it do