Fixed the workflow redis key format used in Client#next_free_workflow_id (#120)

Previously, the wrong key prefix was used, which means that this method
was not actually checking whether a workflow id was already in use.

Author: noahfpf

lib/gush/client.rb

@@ -72,7 +72,7 @@ def next_free_workflow_id
       id = nil
       loop do
         id = SecureRandom.uuid
-        available = !redis.exists?("gush.workflow.#{id}")
+        available = !redis.exists?("gush.workflows.#{id}")
 
         break if available
       end

spec/gush/client_spec.rb

@@ -97,6 +97,37 @@
     end
   end
 
+  describe "#next_free_job_id" do
+    it "returns an id" do
+      expect(client.next_free_job_id('123', Prepare.to_s)).to match(/^\h{8}-\h{4}-(\h{4})-\h{4}-\h{12}$/)
+    end
+
+    it "returns an id that doesn't match an existing job id" do
+      workflow = TestWorkflow.create
+      job = workflow.jobs.first
+
+      second_try_id = '1234'
+      allow(SecureRandom).to receive(:uuid).and_return(job.id, second_try_id)
+
+      expect(client.next_free_job_id(workflow.id, job.class.to_s)).to eq(second_try_id)
+    end
+  end
+
+  describe "#next_free_workflow_id" do
+    it "returns an id" do
+      expect(client.next_free_workflow_id).to match(/^\h{8}-\h{4}-(\h{4})-\h{4}-\h{12}$/)
+    end
+
+    it "returns an id that doesn't match an existing workflow id" do
+      workflow = TestWorkflow.create
+
+      second_try_id = '1234'
+      allow(SecureRandom).to receive(:uuid).and_return(workflow.id, second_try_id)
+
+      expect(client.next_free_workflow_id).to eq(second_try_id)
+    end
+  end
+
   describe "#persist_workflow" do
     it "persists JSON dump of the Workflow and its jobs" do
       job = double("job", to_json: 'json')