public void MathExpressionContext_Can_Forget_Variable()
{
MathExpressionContext context = new MathExpressionContext();
context.Define("x", 42);
Assert.AreEqual(42, context.Resolve("x").Evaluate(context));
context.Forget("x");
var exception = Assert.Throws<MathExpressionException>(() => context.Resolve("x"));
Assert.AreEqual("The variable 'x' has not been defined.", exception.Message);
}
public void MathExpressionContext_Can_Define_And_Resolve_Expression()
{
MathExpressionContext context = new MathExpressionContext();
context.Define("x", 5);
context.Define("y", MathExpression.Parse("5x"));
Assert.AreEqual(25, context.Resolve("y").Evaluate(context));
}
public void MathExpressionContext_Undefined_Variable_Throws()
{
MathExpressionContext context = new MathExpressionContext();
var exception = Assert.Throws<MathExpressionException>(() => context.Resolve("x"));
Assert.AreEqual("The variable 'x' has not been defined.", exception.Message);
}
public void MathExpressionContext_Can_Redefine_Variable()
{
MathExpressionContext context = new MathExpressionContext();
context.Define("x", 42);
Assert.AreEqual(42, context.Resolve("x").Evaluate(context));
context.Define("x", 107);
Assert.AreEqual(107, context.Resolve("x").Evaluate(context));
}
