add tests for FSM#wait_for_state including enforcement that states mu…

…st be symbols

lib/listen/fsm.rb

@@ -53,6 +53,9 @@ def initialize_fsm
     # if not already, waits for a state change (up to timeout seconds--`nil` means infinite)
     # returns truthy iff the transition to one of the desired state has occurred
     def wait_for_state(*wait_for_states, timeout: nil)
+      wait_for_states.each do |state|
+        state.is_a?(Symbol) or raise ArgumentError, "states must be symbols (got #{state.inspect})"
+      end
       @mutex.synchronize do
         if !wait_for_states.include?(@state)
           @state_changed.wait(@mutex, timeout)

spec/lib/listen/fsm_spec.rb

@@ -60,6 +60,44 @@ def initialize
       expect { subject.transition(:started) }.to raise_exception(NoMethodError, /private.*transition/)
       expect { subject.transition!(:started) }.to raise_exception(NoMethodError, /private.*transition!/)
     end
+
+    describe '#wait_for_state' do
+      it 'returns truthy immediately if already in the desired state' do
+        expect(subject.instance_variable_get(:@state_changed)).to_not receive(:wait)
+        result = subject.wait_for_state(:initial)
+        expect(result).to be_truthy
+      end
+
+      it 'waits for the next state change and returns truthy if then in the desired state' do
+        expect(subject.instance_variable_get(:@state_changed)).to receive(:wait).with(anything, anything) do
+          subject.instance_variable_set(:@state, :started)
+        end
+        result = subject.wait_for_state(:started)
+        expect(result).to be_truthy
+      end
+
+      it 'waits for the next state change and returns falsey if then not the desired state' do
+        expect(subject.instance_variable_get(:@state_changed)).to receive(:wait).with(anything, anything)
+        result = subject.wait_for_state(:started)
+        expect(result).to be_falsey
+      end
+
+      it 'passes the timeout: down to wait, if given' do
+        expect(subject.instance_variable_get(:@state_changed)).to receive(:wait).with(anything, 5.0)
+        subject.wait_for_state(:started, timeout: 5.0)
+      end
+
+      it 'passes nil (infinite) timeout: down to wait, if none given' do
+        expect(subject.instance_variable_get(:@state_changed)).to receive(:wait).with(anything, nil)
+        subject.wait_for_state(:started)
+      end
+
+      it 'enforces precondition that states must be symbols' do
+        expect do
+          subject.wait_for_state(:started, 'stopped')
+        end.to raise_exception(ArgumentError, /states must be symbols .*got "stopped"/)
+      end
+    end
   end
 
   context 'FSM with no start state' do