add unit test and sanity test for different dict type

dict.go

@@ -25,6 +25,8 @@ func NewChineseDict(filePath string) (*ChineseDict, error) {
 
 	var lines []string
 	scanner := bufio.NewScanner(file)
+	buf := make([]byte, 0, bufio.MaxScanTokenSize)
+	scanner.Buffer(buf, 5*1024*1024) // 5MB buffer to handle long lines
 	for scanner.Scan() {
 		line := strings.TrimSpace(scanner.Text())
 		if line != "" { // Skip empty lines
@@ -75,6 +77,17 @@ func (cd *ChineseDict) GetRandomCharacter() rune {
 		return 0 // Return null rune if no lines available
 	}
 
+	if len(cd.lines) == 1 {
+		if cd.currentLineIndex == -1 {
+			cd.selectNewRandomLine()
+		}
+		// Get random index
+		randomIndex := rand.Intn(len(cd.currentLineRunes))
+		cd.currentCharIndex = randomIndex + 1 // Move index forward for next call, align with multiline version for testing
+
+		return cd.currentLineRunes[randomIndex]
+	}
+
 	// Keep track of attempts to avoid infinite recursion
 	maxAttempts := len(cd.lines) * 2 // Try each line at least twice
 	attempts := 0

dict_test.go

@@ -48,6 +48,32 @@ func TestDictE2E(t *testing.T) {
 	}
 }
 
+func TestDictE2ESingleLineVer(t *testing.T) {
+	dict, err := NewChineseDict("random_char.txt")
+	if err != nil {
+		t.Fatalf("NewChineseDict failed: %v", err)
+	}
+
+	for range 1000 {
+		char := dict.GetRandomCharacter()
+		fmt.Printf("%c", char)
+		if char == 0 {
+			t.Error("GetRandomCharacter returned null rune")
+		}
+	}
+	fmt.Println()
+
+	count := dict.GetCharacterCount()
+	if count == 0 {
+		t.Error("GetCharacterCount returned 0")
+	}
+
+	count = dict.GetLineCount()
+	if count == 0 {
+		t.Error("GetLineCount returned 0")
+	}
+}
+
 func TestNewChineseDict(t *testing.T) {
 	testContent := `大家好大家好，家人们晚上好
 先点点关注不迷路，点个小红心
@@ -424,3 +450,47 @@ Another行with more混合content。`
 
 	t.Logf("Got %d Chinese and %d English characters", chineseCount, englishCount)
 }
+
+func TestSingleLineContent(t *testing.T) {
+	testContent := `华枝睾吸虫豆卷叶野螟小叶榕木`
+	//黄眉企鹅五房` for multiline false test
+
+	tmpFile := createTestDictFile(t, testContent)
+	defer os.Remove(tmpFile)
+
+	dict, err := NewChineseDict(tmpFile)
+	if err != nil {
+		t.Fatalf("NewChineseDict failed: %v", err)
+	}
+
+	runeInPosition := 0
+	currentPosition := -1
+
+	for range 100 {
+		char := dict.GetRandomCharacter()
+		if char == 0 {
+			t.Error("Got null character")
+			continue
+		}
+
+		if !dict.isValidCharacter(char) {
+			t.Errorf("Got invalid character: '%c' (U+%04X)", char, char)
+			continue
+		}
+
+		if char == '华' || char == '黄' {
+			currentPosition = 0
+		}
+
+		if currentPosition+1 == dict.currentCharIndex {
+			runeInPosition++
+			currentPosition++
+		}
+	}
+
+	if runeInPosition == 100 {
+		t.Error("GetRandomCharacter is not random enough, always returning characters in sequence")
+	}
+
+	t.Logf("Rune in position: %d", runeInPosition)
+}