Test failure path in LLM flow

Author: rowanseymour

flows/actions/testdata/call_llm.json

@@ -24,7 +24,7 @@
             "@input.text"
         ],
         "locals": {
-            "_llm_output": "<FAILED>"
+            "_llm_output": "\u003cFAILED\u003e"
         },
         "inspection": {
             "dependencies": [
@@ -66,26 +66,26 @@
         },
         "events": [
             {
+                "type": "llm_called",
                 "created_on": "2018-10-18T14:20:30.000123456Z",
-                "elapsed_ms": 0,
-                "input": "Hi everybody",
-                "instructions": "Categorize the following text as positive or negative",
+                "step_uuid": "9688d21d-95aa-4bed-afc7-f31b35731a3d",
                 "llm": {
-                    "name": "Claude",
-                    "uuid": "51ade705-8338-40a9-8a77-37657a936966"
+                    "uuid": "51ade705-8338-40a9-8a77-37657a936966",
+                    "name": "Claude"
                 },
-                "output": "You asked:\n\nCategorize the following text as positive or negative\n\nHi everybody",
-                "step_uuid": "9688d21d-95aa-4bed-afc7-f31b35731a3d",
+                "instructions": "Categorize the following text as positive or negative",
+                "input": "Hi everybody",
+                "output": "negative",
                 "tokens_used": 123,
-                "type": "llm_called"
+                "elapsed_ms": 0
             }
         ],
         "templates": [
             "Categorize the following text as positive or negative",
             "@input.text"
         ],
         "locals": {
-            "_llm_output": "You asked:\n\nCategorize the following text as positive or negative\n\nHi everybody"
+            "_llm_output": "negative"
         },
         "inspection": {
             "dependencies": [

test/services/llm.go

@@ -2,6 +2,7 @@ package services
 
 import (
 	"context"
+	"errors"
 	"strings"
 
 	"github.com/nyaruka/goflow/flows"
@@ -16,9 +17,11 @@ func NewLLM() *LLMService {
 
 func (s *LLMService) Response(ctx context.Context, instructions, input string, maxTokens int) (*flows.LLMResponse, error) {
 	var output string
-	if strings.HasPrefix(input, "\\return ") { // an input like "\return foo" will return "foo"
+	if strings.HasPrefix(input, "\\error ") { // an input like "\error foo" will return the error "foo"
+		return nil, errors.New(input[7:])
+	} else if strings.HasPrefix(input, "\\return ") { // an input like "\return foo" will return "foo"
 		output = input[8:]
-	} else if strings.HasPrefix(input, "Categorize") { // instructions like "Categorize... Category2, Category3" will return "Category3"
+	} else if strings.HasPrefix(instructions, "Categorize") { // instructions like "Categorize... Category2, Category3" will return "Category3"
 		words := strings.Fields(instructions)
 		output = words[len(words)-1]
 	} else {