Refactor coin toss input handling to use a mockable prompter interface and add unit tests for user interaction

Author: chrisreddington

internal/cointoss/cointoss.go

@@ -7,9 +7,14 @@ import (
 	"strings"
 	"time"
 
-	ghprompt "github.com/cli/go-gh/v2/pkg/prompter"
+	userPrompt "github.com/cli/go-gh/v2/pkg/prompter"
 )
 
+// prompter interface allows us to mock the prompt functionality in tests
+type prompter interface {
+	Select(prompt string, defaultValue string, options []string) (int, error)
+}
+
 func TossCoin() string {
 	rand.Seed(time.Now().UnixNano())
 	if rand.Float32() < 0.5 {
@@ -27,8 +32,11 @@ func ValidateGuess(guess string) error {
 }
 
 func GetNextGuess() (string, bool) {
+	return GetNextGuessWithPrompter(userPrompt.New(os.Stdin, os.Stdout, os.Stderr))
+}
+
+func GetNextGuessWithPrompter(p prompter) (string, bool) {
 	options := []string{"Heads", "Tails", "Quit"}
-	p := ghprompt.New(os.Stdin, os.Stdout, os.Stderr)
 
 	answer, err := p.Select("What's your next guess? Heads, Tails or Quit?", "Heads", options)
 	if err != nil {

internal/cointoss/cointoss_test.go

@@ -1,9 +1,20 @@
 package cointoss
 
 import (
+	"errors"
 	"testing"
 )
 
+// Mock prompter for testing
+type mockPrompter struct {
+	selectAnswer int
+	selectError  error
+}
+
+func (m *mockPrompter) Select(prompt string, defaultValue string, options []string) (int, error) {
+	return m.selectAnswer, m.selectError
+}
+
 func TestValidateGuess(t *testing.T) {
 	validGuesses := []string{"heads", "heads ", " HEADS", "tails", "TAILS", " tails "}
 	invalidGuesses := []string{"", "foo", "123", "heds", "taol"}
@@ -29,3 +40,67 @@ func TestTossCoin(t *testing.T) {
 		}
 	}
 }
+
+func TestGetNextGuessWithPrompter(t *testing.T) {
+	tests := []struct {
+		name          string
+		selectAnswer  int
+		selectError   error
+		expectedGuess string
+		expectedCont  bool
+	}{
+		{
+			name:          "select heads",
+			selectAnswer:  0,
+			selectError:   nil,
+			expectedGuess: "heads",
+			expectedCont:  true,
+		},
+		{
+			name:          "select tails",
+			selectAnswer:  1,
+			selectError:   nil,
+			expectedGuess: "tails",
+			expectedCont:  true,
+		},
+		{
+			name:          "select quit",
+			selectAnswer:  2,
+			selectError:   nil,
+			expectedGuess: "",
+			expectedCont:  false,
+		},
+		{
+			name:          "error during selection",
+			selectAnswer:  0,
+			selectError:   errors.New("mock error"),
+			expectedGuess: "",
+			expectedCont:  false,
+		},
+		{
+			name:          "error during selection prints error message",
+			selectAnswer:  0,
+			selectError:   errors.New("test error"),
+			expectedGuess: "",
+			expectedCont:  false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mockP := &mockPrompter{
+				selectAnswer: tt.selectAnswer,
+				selectError:  tt.selectError,
+			}
+
+			guess, cont := GetNextGuessWithPrompter(mockP)
+
+			if guess != tt.expectedGuess {
+				t.Errorf("GetNextGuessWithPrompter() guess = %v, want %v", guess, tt.expectedGuess)
+			}
+			if cont != tt.expectedCont {
+				t.Errorf("GetNextGuessWithPrompter() cont = %v, want %v", cont, tt.expectedCont)
+			}
+		})
+	}
+}