public void TestClearVariables()
{
ExpressionTree testTree = new ExpressionTree("A1+2");
testTree.SetVariable("A1", 32);
testTree.SetVariable("B2", -3);
testTree.SetVariable("C3", 2);
Dictionary <string, double> variables = testTree.GetVariables();
Assert.That(3, Is.EqualTo(variables.Count), "Did not set variables in the expressionTree.");
testTree.ClearVariables();
Assert.That(0, Is.EqualTo(variables.Count), "Did not clear variables in the expressionTree.");
}