diff --git a/chat_service.go b/chat_service.go
index e8e6bb7..a444618 100644
--- a/chat_service.go
+++ b/chat_service.go
@@ -9,34 +9,43 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-type ChatService struct {
-	LLM       *LLMClient
-	reasonsDB ReasonDB
+// ChatServiceAPI allows mocking ChatService in other places
+// Only public methods should be included
+
+type ChatServiceAPI interface {
+	HandleChat(c *gin.Context)
 }
 
-func NewChatService(llm *LLMClient, db ReasonDB) *ChatService {
+// ChatService handles chat interactions and orchestrates LLM and DB calls.
+type ChatService struct {
+	LLM       LLMClientAPI
+	reasonsDB ReasonDBAPI
+}
+
+var _ ChatServiceAPI = (*ChatService)(nil)
+
+func NewChatService(llm LLMClientAPI, db ReasonDBAPI) ChatServiceAPI {
 	return &ChatService{LLM: llm, reasonsDB: db}
 }
 
+// HandleChat is the main entrypoint for chat requests. It delegates to modular helpers.
 func (cs *ChatService) HandleChat(c *gin.Context) {
 	ctx := context.Background()
 	req, err := cs.parseRequest(c)
 	if err != nil {
 		return
 	}
-	keywordsResponse, err := cs.getKeywordsResponse(ctx, req.Message)
+	keywords, err := cs.extractKeywords(ctx, req.Message)
 	if err != nil {
-		cs.logChat(req, keywordsResponse, nil, "", err)
-		c.JSON(http.StatusOK, ChatResponse{Match: nil})
+		cs.respondWithError(c, req, keywords, err)
 		return
 	}
-	keywordList := cs.keywordsToStrings(keywordsResponse["keyword"])
-	best, err := cs.findVisitReason(ctx, req, keywordList)
-
+	best, err := cs.findBestReason(ctx, req, keywords)
 	resp := cs.buildResponse(best)
 	c.JSON(http.StatusOK, resp)
 }
 
+// parseRequest parses and validates the incoming chat request.
 func (cs *ChatService) parseRequest(c *gin.Context) (ChatRequest, error) {
 	var req ChatRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
@@ -47,56 +56,36 @@ func (cs *ChatService) parseRequest(c *gin.Context) (ChatRequest, error) {
 	return req, nil
 }
 
-func (cs *ChatService) getKeywordsResponse(ctx context.Context, message string) (map[string]interface{}, error) {
-	keywords, err := cs.LLM.ExtractKeywords(ctx, message)
-	return keywords, err
-}
-
-func (cs *ChatService) keywordsToStrings(kwIface interface{}) []string {
-	var kwArr []string
-	switch v := kwIface.(type) {
-	case []interface{}:
-		for _, item := range v {
-			if s, ok := item.(string); ok {
-				kwArr = append(kwArr, s)
-			}
-		}
-	case []string:
-		kwArr = v
+// extractKeywords gets keywords from the LLM and normalizes them.
+func (cs *ChatService) extractKeywords(ctx context.Context, message string) ([]string, error) {
+	kwResp, err := cs.LLM.ExtractKeywords(ctx, message)
+	if err != nil {
+		return nil, err
 	}
-	return kwArr
+	return cs.keywordsToStrings(kwResp["keyword"]), nil
 }
 
-func (cs *ChatService) findVisitReason(ctx context.Context, req ChatRequest, keywordList []string) (*Reason, error) {
-	logrus.WithFields(logrus.Fields{
-		"keywords": keywordList,
-		"message":  req.Message,
-	}).Info("Finding visit reason candidates")
-
-	candidateReasonse, err := cs.reasonsDB.findCandidates(keywordList)
-	logrus.WithFields(logrus.Fields{
-		"candidates": candidateReasonse,
-		"error":      err,
-	}).Info("Candidate reasons found")
+// findBestReason finds candidate reasons and disambiguates the best match.
+func (cs *ChatService) findBestReason(ctx context.Context, req ChatRequest, keywords []string) (*Reason, error) {
+	cs.logKeywords(keywords, req.Message)
+	candidates, err := cs.reasonsDB.FindCandidates(keywords)
+	cs.logCandidates(candidates, err)
 	if err != nil {
 		return nil, err
 	}
 	bestID := ""
-	if len(candidateReasonse) > 0 {
-		bestID, err = cs.LLM.DisambiguateBestMatch(ctx, req.Message, candidateReasonse)
-		logrus.WithFields(logrus.Fields{
-			"bestID": bestID,
-			"error":  err,
-		}).Info("Disambiguated best match")
+	if len(candidates) > 0 {
+		bestID, err = cs.LLM.DisambiguateBestMatch(ctx, req.Message, candidates)
+		cs.logBestID(bestID, err)
 	}
-	reason, err := cs.reasonsDB.findById(bestID)
+	reason, err := cs.reasonsDB.FindById(bestID)
 	if err != nil {
-		return nil, fmt.Errorf("findById: %w", err)
+		return nil, fmt.Errorf("FindById: %w", err)
 	}
 	return &reason, nil
-
 }
 
+// buildResponse constructs the ChatResponse from the best Reason.
 func (cs *ChatService) buildResponse(best *Reason) ChatResponse {
 	if best == nil {
 		resp := ChatResponse{Match: nil}
@@ -115,8 +104,65 @@ func (cs *ChatService) buildResponse(best *Reason) ChatResponse {
 	return resp
 }
 
-func (cs *ChatService) logChat(req ChatRequest, keywords map[string]interface{}, candidates []Reason, bestID string, err error) {
-	logRequest(req, keywords, candidates, bestID, err)
+// respondWithError logs and responds with error details.
+func (cs *ChatService) respondWithError(c *gin.Context, req ChatRequest, keywords []string, err error) {
+	kwMap := map[string]interface{}{"keyword": keywords}
+	cs.logChat(req, kwMap, nil, "", err)
+	c.JSON(http.StatusOK, ChatResponse{Match: nil})
+}
+
+// keywordsToStrings normalizes keyword interface to []string.
+func (cs *ChatService) keywordsToStrings(kwIface interface{}) []string {
+	var kwArr []string
+	switch v := kwIface.(type) {
+	case []interface{}:
+		for _, item := range v {
+			if s, ok := item.(string); ok {
+				kwArr = append(kwArr, s)
+			}
+		}
+	case []string:
+		kwArr = v
+	}
+	return kwArr
+}
+
+// logKeywords logs extracted keywords.
+func (cs *ChatService) logKeywords(keywords []string, message string) {
+	logrus.WithFields(logrus.Fields{
+		"keywords": keywords,
+		"message":  message,
+	}).Info("Finding visit reason candidates")
+}
+
+// logCandidates logs candidate reasons.
+func (cs *ChatService) logCandidates(candidates []Reason, err error) {
+	logrus.WithFields(logrus.Fields{
+		"candidates": candidates,
+		"error":      err,
+	}).Info("Candidate reasons found")
+}
+
+// logBestID logs the best candidate ID.
+func (cs *ChatService) logBestID(bestID string, err error) {
+	logrus.WithFields(logrus.Fields{
+		"bestID": bestID,
+		"error":  err,
+	}).Info("Disambiguated best match")
+}
+
+// logChat logs the chat request and result details.
+func (cs *ChatService) logChat(req ChatRequest, keywords interface{}, candidates []Reason, bestID string, err error) {
+	var kwMap map[string]interface{}
+	switch v := keywords.(type) {
+	case []string:
+		kwMap = map[string]interface{}{"keyword": v}
+	case map[string]interface{}:
+		kwMap = v
+	default:
+		kwMap = map[string]interface{}{"keyword": v}
+	}
+	logRequest(req, kwMap, candidates, bestID, err)
 	if candidates != nil && bestID != "" {
 		var best *Reason
 		for i := range candidates {
diff --git a/chat_service_integration_test.go b/chat_service_integration_test.go
new file mode 100644
index 0000000..5f94655
--- /dev/null
+++ b/chat_service_integration_test.go
@@ -0,0 +1,176 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+// --- Mocks ---
+type mockLLM struct {
+	keywordsResp map[string]interface{}
+	disambigID   string
+	keywordsErr  error
+	disambigErr  error
+}
+
+var _ LLMClientAPI = (*mockLLM)(nil)
+
+func (m *mockLLM) ExtractKeywords(ctx context.Context, msg string) (map[string]interface{}, error) {
+	return m.keywordsResp, m.keywordsErr
+}
+func (m *mockLLM) DisambiguateBestMatch(ctx context.Context, msg string, candidates []Reason) (string, error) {
+	return m.disambigID, m.disambigErr
+}
+
+// --- Test ReasonDB ---
+type testReasonDB struct {
+	candidates []Reason
+	findErr    error
+	byID       map[string]Reason
+}
+
+var _ ReasonDBAPI = (*testReasonDB)(nil)
+
+func (db *testReasonDB) FindCandidates(keywords []string) ([]Reason, error) {
+	return db.candidates, db.findErr
+}
+func (db *testReasonDB) FindById(id string) (Reason, error) {
+	r, ok := db.byID[id]
+	if !ok {
+		return Reason{}, context.DeadlineExceeded
+	}
+	return r, nil
+}
+
+// --- Integration tests ---
+func TestChatService_MatchFound(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	var llm LLMClientAPI = &mockLLM{
+		keywordsResp: map[string]interface{}{"keyword": []string{"worms", "deworming"}},
+		disambigID:   "deworming",
+	}
+	reason := Reason{
+		ID:         "deworming",
+		Procedures: []Procedure{{Name: "Deworming tablet", Price: 30, DurationMin: 10}},
+		Notes:      "Bloodwork ensures organs are safe for treatment.",
+	}
+	var db ReasonDBAPI = &testReasonDB{
+		candidates: []Reason{reason},
+		byID:       map[string]Reason{"deworming": reason},
+	}
+	var cs ChatServiceAPI = NewChatService(llm, db)
+	r := gin.New()
+	r.POST("/chat", cs.HandleChat)
+
+	w := httptest.NewRecorder()
+	body := map[string]string{"message": "My dog needs deworming"}
+	jsonBody, _ := json.Marshal(body)
+	req, _ := http.NewRequest("POST", "/chat", httptestNewBody(jsonBody))
+	req.Header.Set("Content-Type", "application/json")
+
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusOK {
+		t.Fatalf("Expected 200, got %d", w.Code)
+	}
+	var resp ChatResponse
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("Invalid response: %v", err)
+	}
+	if resp.Match == nil || *resp.Match != "deworming" {
+		t.Errorf("Expected match 'deworming', got %v", resp.Match)
+	}
+	if len(resp.Procedures) != 1 || resp.Procedures[0].Name != "Deworming tablet" {
+		t.Errorf("Expected procedure 'Deworming tablet', got %+v", resp.Procedures)
+	}
+	if resp.Notes != reason.Notes {
+		t.Errorf("Expected notes '%s', got '%s'", reason.Notes, resp.Notes)
+	}
+}
+
+func TestChatService_NoMatch(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	llm := &mockLLM{
+		keywordsResp: map[string]interface{}{"keyword": []string{"unknown"}},
+		disambigID:   "",
+	}
+	db := &testReasonDB{
+		candidates: []Reason{},
+		byID:       map[string]Reason{},
+	}
+	cs := NewChatService(llm, db)
+	r := gin.New()
+	r.POST("/chat", cs.HandleChat)
+
+	w := httptest.NewRecorder()
+	body := map[string]string{"message": "No known reason"}
+	jsonBody, _ := json.Marshal(body)
+	req, _ := http.NewRequest("POST", "/chat", httptestNewBody(jsonBody))
+	req.Header.Set("Content-Type", "application/json")
+
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusOK {
+		t.Fatalf("Expected 200, got %d", w.Code)
+	}
+	var resp ChatResponse
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("Invalid response: %v", err)
+	}
+	if resp.Match != nil {
+		t.Errorf("Expected no match, got %v", resp.Match)
+	}
+}
+
+func TestChatService_LLMError(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	llm := &mockLLM{
+		keywordsErr: context.DeadlineExceeded,
+	}
+	db := &testReasonDB{}
+	cs := NewChatService(llm, db)
+	r := gin.New()
+	r.POST("/chat", cs.HandleChat)
+
+	w := httptest.NewRecorder()
+	body := map[string]string{"message": "error"}
+	jsonBody, _ := json.Marshal(body)
+	req, _ := http.NewRequest("POST", "/chat", httptestNewBody(jsonBody))
+	req.Header.Set("Content-Type", "application/json")
+
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusOK {
+		t.Fatalf("Expected 200, got %d", w.Code)
+	}
+	var resp ChatResponse
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("Invalid response: %v", err)
+	}
+	if resp.Match != nil {
+		t.Errorf("Expected no match on LLM error, got %v", resp.Match)
+	}
+}
+
+// --- Helper for request body ---
+func httptestNewBody(b []byte) *httptestBody {
+	return &httptestBody{b: b}
+}
+
+type httptestBody struct {
+	b   []byte
+	pos int
+}
+
+func (r *httptestBody) Read(p []byte) (int, error) {
+	if r.pos >= len(r.b) {
+		return 0, io.EOF
+	}
+	n := copy(p, r.b[r.pos:])
+	r.pos += n
+	return n, nil
+}
+func (r *httptestBody) Close() error { return nil }
diff --git a/db.go b/db.go
index 4df460e..deab67e 100644
--- a/db.go
+++ b/db.go
@@ -22,7 +22,7 @@ func NewReasonDB() ReasonDB {
 	db.init()
 	return db
 }
-func (rdb *ReasonDB) findById(reasonId string) (Reason, error) {
+func (rdb *ReasonDB) FindById(reasonId string) (Reason, error) {
 	for _, reason := range rdb.reasonsDB {
 		if reason.ID == reasonId {
 			return reason, nil
@@ -73,8 +73,8 @@ func (rdb *ReasonDB) indexReasons(reasons []Reason) error {
 	return rdb.reasonsIdx.Batch(batch)
 }
 
-// findCandidates returns reasons with overlapping keywords
-func (rdb *ReasonDB) findCandidates(keywords []string) ([]Reason, error) {
+// FindCandidates returns reasons with overlapping keywords
+func (rdb *ReasonDB) FindCandidates(keywords []string) ([]Reason, error) {
 	query := bleve.NewMatchQuery(strings.Join(keywords, " "))
 	search := bleve.NewSearchRequest(query)
 	searchResults, err := rdb.reasonsIdx.Search(search)
@@ -104,3 +104,13 @@ func sumProcedures(procs []Procedure) (int, int) {
 	}
 	return totalPrice, totalDuration
 }
+
+// ReasonDBAPI allows mocking ReasonDB in other places
+// Only public methods should be included
+
+type ReasonDBAPI interface {
+	FindById(reasonId string) (Reason, error)
+	FindCandidates(keywords []string) ([]Reason, error)
+}
+
+var _ ReasonDBAPI = (*ReasonDB)(nil)
diff --git a/llm.go b/llm.go
index a653201..4836557 100644
--- a/llm.go
+++ b/llm.go
@@ -18,6 +18,14 @@ type LLMClient struct {
 	BaseURL string
 }
 
+// NewLLMClient constructs a new LLMClient with the given API key and base URL
+func NewLLMClient(apiKey, baseURL string) *LLMClient {
+	return &LLMClient{
+		APIKey:  apiKey,
+		BaseURL: baseURL,
+	}
+}
+
 // renderPrompt renders a Go template with the given data
 func renderPrompt(tmplStr string, data any) (string, error) {
 	tmpl, err := template.New("").Parse(tmplStr)
@@ -133,3 +141,13 @@ func (llm *LLMClient) openAICompletion(ctx context.Context, prompt string, forma
 	logrus.WithField("content", result.Message.Content).Info("[LLM] openAICompletion: got content")
 	return result.Message.Content, nil
 }
+
+// LLMClientAPI allows mocking LLMClient in other places
+// Only public methods should be included
+
+type LLMClientAPI interface {
+	ExtractKeywords(ctx context.Context, message string) (map[string]interface{}, error)
+	DisambiguateBestMatch(ctx context.Context, message string, candidates []Reason) (string, error)
+}
+
+var _ LLMClientAPI = (*LLMClient)(nil)
diff --git a/main.go b/main.go
index 369f34a..0cc512c 100644
--- a/main.go
+++ b/main.go
@@ -20,11 +20,11 @@ func main() {
 	if err := loadUITemplate("ui.html"); err != nil {
 		logrus.Fatalf("Failed to load ui.html: %v", err)
 	}
-	llm := &LLMClient{
-		APIKey:  os.Getenv("OPENAI_API_KEY"),
-		BaseURL: os.Getenv("OPENAI_BASE_URL"),
-	}
-	chatService := NewChatService(llm, reasonDB)
+	var llm LLMClientAPI = NewLLMClient(
+		os.Getenv("OPENAI_API_KEY"),
+		os.Getenv("OPENAI_BASE_URL"),
+	)
+	chatService := NewChatService(llm, &reasonDB)
 	r := gin.Default()
 	r.GET("/", func(c *gin.Context) {
 		c.Status(200)
diff --git a/main_test.go b/main_test.go
deleted file mode 100644
index cbe6193..0000000
--- a/main_test.go
+++ /dev/null
@@ -1,145 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"encoding/json"
-	"io"
-	"net/http"
-	"net/http/httptest"
-	"os"
-	"testing"
-
-	"github.com/gin-gonic/gin"
-)
-
-type testDB struct {
-	file string
-	data string
-}
-
-func (tdb *testDB) setup() {
-	err := os.WriteFile(tdb.file, []byte(tdb.data), 0644)
-	if err != nil {
-		panic(err)
-	}
-}
-
-func (tdb *testDB) teardown() {
-	_ = os.Remove(tdb.file)
-}
-
-func TestChatEndpoint_MatchFound(t *testing.T) {
-	tdb := testDB{
-		file: "db.yaml",
-		data: `
-- id: deworming
-  reason: Deworming for dogs
-  keywords: ["worms", "deworming", "parasite"]
-  procedures:
-    - name: Deworming tablet
-      price: 30
-      duration_minutes: 10
-    - name: Bloodwork
-      price: 35
-      duration_minutes: 35
-  notes: Bloodwork ensures organs are safe for treatment.
-- id: vaccination
-  reason: Annual vaccination
-  keywords: ["vaccine", "vaccination", "shots"]
-  procedures:
-    - name: Vaccine injection
-      price: 50
-      duration_minutes: 15
-`,
-	}
-	tdb.setup()
-	defer tdb.teardown()
-
-	if err := loadYAMLDB(tdb.file); err != nil {
-		t.Fatalf("Failed to load test db: %v", err)
-	}
-
-	r := setupRouter()
-
-	w := httptest.NewRecorder()
-	body := map[string]string{"message": "My dog needs deworming and bloodwork"}
-	jsonBody, _ := json.Marshal(body)
-	req, _ := http.NewRequest("POST", "/chat", bytes.NewBuffer(jsonBody))
-	req.Header.Set("Content-Type", "application/json")
-
-	r.ServeHTTP(w, req)
-
-	if w.Code != http.StatusOK {
-		t.Fatalf("Expected 200, got %d", w.Code)
-	}
-	respBody, _ := io.ReadAll(w.Body)
-	if !bytes.Contains(respBody, []byte("deworming")) {
-		t.Errorf("Expected match for deworming, got %s", string(respBody))
-	}
-}
-
-func TestChatEndpoint_NoMatch(t *testing.T) {
-	tdb := testDB{
-		file: "db.yaml",
-		data: `
-- id: vaccination
-  reason: Annual vaccination
-  keywords: ["vaccine", "vaccination", "shots"]
-  procedures:
-    - name: Vaccine injection
-      price: 50
-      duration_minutes: 15
-`,
-	}
-	tdb.setup()
-	defer tdb.teardown()
-
-	if err := loadYAMLDB(tdb.file); err != nil {
-		t.Fatalf("Failed to load test db: %v", err)
-	}
-
-	r := setupRouter()
-
-	w := httptest.NewRecorder()
-	body := map[string]string{"message": "My dog has worms"}
-	jsonBody, _ := json.Marshal(body)
-	req, _ := http.NewRequest("POST", "/chat", bytes.NewBuffer(jsonBody))
-	req.Header.Set("Content-Type", "application/json")
-
-	r.ServeHTTP(w, req)
-
-	if w.Code != http.StatusOK {
-		t.Fatalf("Expected 200, got %d", w.Code)
-	}
-	respBody, _ := io.ReadAll(w.Body)
-	if !bytes.Contains(respBody, []byte(`"match":null`)) {
-		t.Errorf("Expected no match, got %s", string(respBody))
-	}
-}
-
-func setupRouter() *gin.Engine {
-	r := gin.Default()
-	r.POST("/chat", func(c *gin.Context) {
-		var req ChatRequest
-		if err := c.ShouldBindJSON(&req); err != nil {
-			c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid request"})
-			return
-		}
-		keywords := naiveKeywordExtract(req.Message)
-		candidates := findCandidates(keywords)
-		if len(candidates) == 0 {
-			c.JSON(http.StatusOK, ChatResponse{Match: nil})
-			return
-		}
-		best := candidates[0]
-		totalPrice, totalDuration := sumProcedures(best.Procedures)
-		c.JSON(http.StatusOK, ChatResponse{
-			Match:         &best.ID,
-			Procedures:    best.Procedures,
-			TotalPrice:    totalPrice,
-			TotalDuration: totalDuration,
-			Notes:         best.Notes,
-		})
-	})
-	return r
-}