public void TestAppendString(ConditionalOperation op, string expected)
{
ExpressionBase variable = (op == ConditionalOperation.Not) ? null : new VariableExpression("variable");
var value = new IntegerConstantExpression(99);
var expr = new ConditionalExpression(variable, op, value);
var builder = new StringBuilder();
expr.AppendString(builder);
Assert.That(builder.ToString(), Is.EqualTo(expected));
}