Add TestSpell function in spelling_test.go

Added a new unit test, TestSpell, to the spelling_test.go file. This new test safely triggers several different spell checking scenarios, from empty strings to non-alphabetical characters. As a result, the function's reliability and robustness is significantly improved.

spelling_test.go

@@ -51,3 +51,62 @@ func TestConvertByteToWord(t *testing.T) {
 		})
 	}
 }
+
+func TestSpell(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   string
+		want    string
+		wantErr bool
+	}{
+		{
+			name:    "empty string",
+			input:   "",
+			want:    "",
+			wantErr: false,
+		},
+		{
+			name:    "single character",
+			input:   "a",
+			want:    "alfa",
+			wantErr: false,
+		},
+		{
+			name:    "multiple characters",
+			input:   "abc",
+			want:    "alfa/bravo/charlie",
+			wantErr: false,
+		},
+		{
+			name:    "non-alphabetic character",
+			input:   "1",
+			want:    "ONE",
+			wantErr: false,
+		},
+		{
+			name:    "mixed alphabetic and non-alphabetic characters",
+			input:   "a1",
+			want:    "alfa/ONE",
+			wantErr: false,
+		},
+		{
+			name:    "not supported characters",
+			input:   "üäö߀",
+			want:    "",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := Spell(tt.input)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Spell() error = %s, wantErr %t", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("Spell() = %s, want %s", got, tt.want)
+			}
+		})
+	}
+}