diff --git a/src/components/Epochs.js b/src/components/Epochs.js
index 6a940c3..3764d10 100644
--- a/src/components/Epochs.js
+++ b/src/components/Epochs.js
@@ -39,7 +39,7 @@ const Epochs = ({epochs, errors, dispatch}) => {
   }
   
   const renderAddEpochButton = index => {
-    if (index === epochs.length - 1 ) return (
+    if (epochs && index === epochs.length - 1 ) return (
       <form onSubmit={e=>addEpoch(e)}>
         <input className="form form--add" type="submit" name="add-epoch" value="Add Epoch" ></input>
       </form>
@@ -48,7 +48,7 @@ const Epochs = ({epochs, errors, dispatch}) => {
   }
 
   const renderEpochs = () => {
-    if (epochs.length) return epochs.map((epoch, index) => {
+    if (epochs && epochs.length) return epochs.map((epoch, index) => {
       const epochError = errors.epoch ? errors.error : null
       return (
       <div 
diff --git a/src/reducers/reducer.epochs.test.js b/src/reducers/reducer.epochs.test.js
index 644302f..f2e4cd4 100644
--- a/src/reducers/reducer.epochs.test.js
+++ b/src/reducers/reducer.epochs.test.js
@@ -6,7 +6,8 @@ describe('Epochs', () => {
     state.epochs = [
       {
         name: 'epoch 1',
-        changes: ['']
+        changes: [''],
+        parent: null
       }
     ]
   })
@@ -17,7 +18,7 @@ describe('Epochs', () => {
   });
 
   it('epochs addition returns new epochs list', () => {
-    const action = {type: 'ADD_EPOCH', value: { name: 'epoch 2', changes: ['']}};
+    const action = {type: 'ADD_EPOCH', value: { name: 'epoch 2', changes: [''], parent: null}};
     expect(stateReducer(state, action)).toEqual({...state, epochs: [...state.epochs, action.value]})
   })
   
@@ -28,8 +29,8 @@ describe('Epochs', () => {
     expect(stateReducer(secondState, secondAction)).toEqual(
       {...state, 
         epochs: [
-          {name: 'proto-lang', changes: ['']},
-          {name: 'epoch 2', changes: ['']}
+          {name: 'proto-lang', changes: [''], parent: null},
+          {name: 'epoch 2', changes: [''], parent: null}
         ]
       }
     );
@@ -42,8 +43,8 @@ describe('Epochs', () => {
     expect(stateReducer(secondState, secondAction)).toEqual(
       {...state, 
         epochs: [
-          {name: 'epoch 1', changes: ['n>t/_#', '[+plosive]>[+nasal -plosive]/_n']},
-          {name: 'epoch 2', changes: ['']}
+          {name: 'epoch 1', changes: ['n>t/_#', '[+plosive]>[+nasal -plosive]/_n'], parent: null},
+          {name: 'epoch 2', changes: [''], parent: null}
         ]
       }
       );
@@ -55,7 +56,7 @@ describe('Epochs', () => {
       const secondAction = {type: 'REMOVE_EPOCH', value: {index: 0, name: 'epoch 1'}}
       expect(stateReducer(stateWithTwoEpochs, secondAction)).toEqual({
         ...state,
-        epochs: [{ name: 'epoch 2', changes: ['']}]
+        epochs: [{ name: 'epoch 2', changes: [''], parent: null}]
       });
   });
 
diff --git a/src/reducers/reducer.results.test.js b/src/reducers/reducer.results.test.js
index 2218080..43b7b9e 100644
--- a/src/reducers/reducer.results.test.js
+++ b/src/reducers/reducer.results.test.js
@@ -22,43 +22,99 @@ describe('Results', () => {
   it('rule without ">" returns helpful error message', () => {
     const { phones } = initState();
     const epoch = { name: 'error epoch', changes: [ 't/n/_' ] }
-    expect(decomposeRules(epoch, phones)).toEqual("Error in line 1: Insert '>' operator between target and result");
+    const errorMessage = {epoch: 'error epoch', error: "Error in line 1: Insert '>' operator between target and result"};
+    let receivedError;
+    try {
+      decomposeRules(epoch, phones)
+    }
+    catch (err) {
+      receivedError=err;
+    }
+    expect(receivedError).toStrictEqual(errorMessage);
   })
-
+  
   it('rule with too many ">" returns helpful error message', () => {
     const { phones } = initState();
     const epoch = { name: 'error epoch', changes: [ 't>n>/_' ] }
-    expect(decomposeRules(epoch, phones)).toEqual("Error in line 1: Too many '>' operators");
+    const errorMessage = {epoch: 'error epoch', error: "Error in line 1: Too many '>' operators"};
+    let receivedError;
+    try {
+      decomposeRules(epoch, phones)
+    }
+    catch (err) {
+      receivedError=err;
+    }
+    expect(receivedError).toStrictEqual(errorMessage);
   })
-
+  
   it('rule without "/" returns helpful error message', () => {
     const { phones } = initState();
     const epoch = { name: 'error epoch', changes: [ 't>n_' ] }
-    expect(decomposeRules(epoch, phones)).toEqual("Error in line 1: Insert '/' operator between change and environment");
+    const errorMessage = {epoch: 'error epoch', error: "Error in line 1: Insert '/' operator between change and environment"};
+    let receivedError;
+    try {
+      decomposeRules(epoch, phones)
+    }
+    catch (err) {
+      receivedError=err;
+    }
+    expect(receivedError).toStrictEqual(errorMessage);
   })
-
+  
   it('rule with too many "/" returns helpful error message', () => {
     const { phones } = initState();
     const epoch = { name: 'error epoch', changes: [ 't>n/_/' ] }
-    expect(decomposeRules(epoch, phones)).toEqual("Error in line 1: Too many '/' operators");
+    const errorMessage = {epoch: 'error epoch', error: "Error in line 1: Too many '/' operators"};
+    let receivedError;
+    try {
+      decomposeRules(epoch, phones)
+    }
+    catch (err) {
+      receivedError=err;
+    }
+    expect(receivedError).toStrictEqual(errorMessage);
   })
-
+  
   it('rule without "_" returns helpful error message', () => {
     const { phones } = initState();
     const epoch = { name: 'error epoch', changes: [ 't>n/' ] }
-    expect(decomposeRules(epoch, phones)).toEqual("Error in line 1: Insert '_' operator in environment");
+    const errorMessage = {epoch: 'error epoch', error: "Error in line 1: Insert '_' operator in environment"};
+    let receivedError;
+    try {
+      decomposeRules(epoch, phones)
+    }
+    catch (err) {
+      receivedError=err;
+    }
+    expect(receivedError).toStrictEqual(errorMessage);
   })
-
+  
   it('rule with too many "_" returns helpful error message', () => {
     const { phones } = initState();
     const epoch = { name: 'error epoch', changes: [ 't>n/__' ] }
-    expect(decomposeRules(epoch, phones)).toEqual("Error in line 1: Too many '_' operators");
+    const errorMessage = {epoch: 'error epoch', error: "Error in line 1: Too many '_' operators"};
+    let receivedError;
+    try {
+      decomposeRules(epoch, phones)
+    }
+    catch (err) {
+      receivedError=err;
+    }
+    expect(receivedError).toStrictEqual(errorMessage);
   })
-
+  
   it('rule with incorrect feature syntax returns helpful error message', () => {
     const { phones } = initState();
     const epoch = { name: 'error epoch', changes: [ '[+ occlusive - nasal = obstruent]>n/_' ] }
-    expect(decomposeRules(epoch, phones)).toEqual("Error in line 1: Unknown token '='");
+    const errorMessage = {epoch: 'error epoch', error: "Error in line 1: Unknown token '='"};
+    let receivedError;
+    try {
+      decomposeRules(epoch, phones)
+    }
+    catch (err) {
+      receivedError=err;
+    }
+    expect(receivedError).toStrictEqual(errorMessage);
   })
 
   it('expect transform lexeme to apply rule to lexeme', () => {